Category: Solar 101

How many solar panels do I need to power my home?

How many solar panels do I need to power my home?

How many solar panels do I need to power my home?

Solar systems are sized based on your energy usage in kilowatt-hours (kWh). But if you don’t have those numbers handy, this article offers ballpark system sizes based on familiar reference points, like square footage or number of bedrooms in your home.

When people first consider the idea of going solar, one of the very first questions that comes to mind is “how many solar panels do I need to power my home?”

Though the only accurate and reliable way to size a solar system is based on your personal energy usage, we understand not everyone has that information readily accessible. For those of you just beginning your solar research, we wanted to provide benchmark system sizes based on familiar reference points, like square footage and number of bedrooms in your home, to give you a starting point for your research.

Before we go further, we should be clear: these tables are estimates projected based on US national averages. Your energy needs may differ from what is typical of the average American home.

These tables give a benchmark to help you answer preliminary questions like how many panels can fit on your roof and whether going solar fits within your budget. If you decide to move forward, you will need to gather energy usage data and size a system around your individual needs.

Jump to the data:

How many solar panels do I need…

Methodology

We referenced US Census data on average household energy usage, cost of electricity, and occupancy per square foot in the US to work out these projections. In all cases, the tables shown reflects how many solar panels you would need to fully power an “average” American home based on the data available to us.

Because panels come in a wide range of wattages, we’ve run the numbers for two different panel sizes: 315W and 375W. If you opt for lower-efficiency panels, you’ll need more panels in your array to hit the target production number.

Keep this in mind if space is a concern. With limited roof space, you may need to invest in more efficient panels to be able to fit the array on your roof. We’ve provided a range in our projections (from 315W to 375W) to give you a sense of how much it impacts the physical layout of the array.

How many solar panels do I need based on the square footage of my house?

Know the square footage of your home? This table cross-references on US Census data on the average household square footage against the average monthly electric usage of an American household to estimate how many panels you may need based on the size of your home.

Square FootageTypical System Size# of panels (375W)# of panels (315W)Sample System
2500.66 kW23Shop
5001.33 kW45Shop
7501.99 kW67Shop
1,0002.66 kW89Shop
1,2503.32 kW911Shop
1,5003.99 kW1113Shop
1,7504.65 kW1315Shop
2,0005.32 kW1517Shop
2,2505.98 kW1619Shop
2,5006.65 kW1822Shop
2,7507.31 kW2024Shop
3,0007.98 kW2226Shop
3,2508.64 kW2428Shop
3,5009.31 kW2530Shop
3,7509.97 kW2732Shop
4,00010.64 kW2934Shop
4,25011.30 kW3136Shop
4,50011.97 kW3238Shop
4,75012.63 kW3441Shop
5,00013.30 kW3643Shop

How many solar panels do I need based on the number of bedrooms in my home?

If you don’t know the square footage of your house off the top of your head, we’ve also estimated average system size based on the number of bedrooms in your home. 

These estimates are based on research from the NAHB (National Association of Homebuilders) which reports the average American home has 3.38 bedrooms. We’ve referenced that figure against the average monthly electric usage of an American household to produce the table below.

BedroomsTypical System Size# of panels (375W)# of panels (315W)Sample System
11.94 kW67Shop
23.88 kW1113Shop
35.82 kW1619Shop
47.75 kW2125Shop
59.69 kW2631Shop
611.63 kW3237Shop

How many solar panels do I need to eliminate my electric bill?

Lastly, let’s assume you pay the national average rate for electricity, which is 13.3 cents/kWh.  Here’s how many solar panels you would need based on your average monthly electric bill.

Electric BillTypical System Size# of panels (375W)# of panels (315W)Sample System
$201.08 kW34Shop
$402.16 kW67Shop
$603.23 kW911Shop
$804.31 kW1214Shop
$1005.39 kW1518Shop
$1206.47 kW1821Shop
$1407.55 kW2124Shop
$1608.62 kW2328Shop
$1809.70 kW2631Shop
$20010.78 kW2935Shop
$22512.13 kW3339Shop
$25013.47 kW3643Shop
$27514.82 kW4048Shop
$30016.17 kW4452Shop
$32517.52 kW4756Shop
$35018.86 kW5160Shop
$37520.21 kW5465Shop
$40021.56 kW5869Shop

How many solar panels do you need based on your kWh usage?

The tables above simply give a starting point to get you in the ballpark. If you decide to move forward with your project, you’ll need to go through a more accurate sizing process based on your personal energy usage.

Energy usage is measured in kilowatt-hours (kWh), which can be found on your monthly electric bill. 

Ideally, you want to base your system design off the past 12 months of electric bills, to account for peaks and valleys in usage. Bills tend to be higher during summer and winter due to the need to run A/C and heat.

The table below shows benchmark system sizes based on your average monthly energy usage. This is the most accurate way to size out your system, so if you have your energy usage data available, we’d recommend starting here.

Monthly kWh UsageTypical System Size# of panels (375W)# of panels (315W)Sample System
1000.72 kW23Shop
2001.43 kW45Shop
3002.15 kW67Shop
4002.87 kW810Shop
5003.58 kW1012Shop
6004.30 kW1214Shop
7005.02 kW1416Shop
8005.73 kW1619Shop
9006.45 kW1821Shop
1,0007.17 kW2023Shop
1,2008.60 kW2328Shop
1,40010.04 kW2732Shop
1,60011.47 kW3137Shop
1,80012.90 kW3541Shop
2,00014.34 kW3946Shop
2,25016.13 kW4452Shop
2,50017.92 kW4857Shop
2,75019.71 kW5363Shop
3,00021.51 kW5869Shop

To hone in on a more accurate figure, head over to our solar cost calculator and enter your ZIP code and energy usage data. We’ll provide an accurate cost and system size estimate that takes your usage and local climate into account.

Download our free solar panel buying guide!
What is a micro-inverter?

What is a micro-inverter?

What is a micro-inverter?

A micro-inverter is device that connects to a single solar panel, converting DC (direct current) from the panel into AC (alternating current), which can power household appliances or be sent into the grid for energy credits. Unlike string inverters, micro-inverters control the output of a single panel. This article outlines the pros and cons of using micro-inverters in your solar power system.

In solar power systems, the inverter is like the brain of the system. It takes the DC (direct current) electricity produced by solar panels and converts it into AC (alternating current), a format that can be used to power your appliances and sent into the utility grid.

Traditional inverters, called string inverters, are designed to manage groups (or series strings) of panels plugged into an input on the inverter. For example, you might wire 24 solar panels into an SMA Sunny Boy inverter in two strings.

But micro-inverters are different. In a micro-inverter system, each micro-inverter is paired to its own panel. So in the same 24-panel system, you would have 24 micro-inverters installed—one on each panel.

On a per-panel basis, micro-inverters like the Enphase IQ7+ cost a bit more than basic string inverters. But micro-inverters come with features that can optimize the overall output of your system, providing a boost in efficiency that offsets the higher up-front cost.

In this article, we’ll explain what a micro-inverter is, then outline the pros and cons of micro-inverters to help you decide whether you should consider them for your solar project.

What is a micro-inverter?

In simple terms, a micro-inverter is an inverter that controls the output of a single solar panel. Each micro-inverter that is paired with a solar panel essentially creates a self-contained solar energy system. 

Mount it to the back of the panel, plug it in, and you’ve got a system that produces energy, regardless of whether you’ve installed 1 panel or 100.

Advantages of Micro-Inverters

Due to the way they’re configured, micro-inverters have a few key advantages compared to string inverters that justify the higher price tag.

Power Optimization

In order to explain the problem micro-inverters are built to solve, we first need a bit of background context about how string inverters work.

With a traditional string inverter, groups of panels are wired in series. If you have 8 panels in a string, all 8 panels are part of the same circuit, which means they are subject to the same electrical characteristics. 

If the output of a single panel drops, the whole circuit drops to match the reduced output of the under-performing panel. You might have a string of 350W panels, but if one panel falls to 300W output, every panel in the string is restricted to that 300W mark.

Using string inverters, a drop in production from one panel drags down the output of the rest of the array.

With micro-inverters, each panel is isolated from the rest of the array. One shaded panel may drop to 300W, but the rest of the panels remain unaffected and continue to produce at its 350W capacity.

With micro-inverters, a drop in production from one panel doesn't affect the rest of the array.

The net result is that micro-inverters allow you to produce more power out of the same panels. In areas where trees or other obstructions will cast shade on your panels, micro-inverters are well worth the investment. 

Isolated Equipment Failure

Similar to the above point, if a piece of equipment fails completely, the rest of the array won’t be affected. 

Let’s say a panel malfunctions due to faulty wiring and stops producing power. With micro-inverters, that panel is isolated, so the rest of the array keeps producing power. The other panels will continue to work, so you are not stuck without a working system while you file a warranty claim and get it replaced.

With a traditional string inverter like the SMA Sunny Boy, the entire string could be affected to the point where the inverter wouldn’t produce power. You could potentially be left in the dark until you replace the faulty panel.

Ease of Installation

Micro-inverters use standard AC wiring, similar to what is used throughout your house. They are also plug-and-play, with each unit plugging into the next. 

As a result, micro-inverters are extremely easy to install and connect because they use standard AC wiring and it only takes a few seconds to plug in each unit. 

Expandable Design

What if you want to start small and expand your system later? Maybe you don’t have the budget to offset 100% of your energy usage, but you want to get into a smaller system so you can start reaping the benefits of solar. Or maybe you want a self-contained array to power your shed as a “test run” to see if it makes sense to power the rest of your home with solar.

Due to their 1-to-1 nature, systems with micro-inverters can essentially be as small or as large as you want them. If you want, you can start with a single panel+micro-inverter pairing. Adding more panels later isn’t a problem, because none of the existing equipment needs to be moved or re-wired to facilitate the addition.

The same isn’t possible with string inverters, which have minimum string size requirements because the panels need to supply enough voltage to the inverter to power it on. In the linked example, the system is limited to 7-10 panels per string. Outside that range, the inverter may not function properly.

Which means that if you have any future plans for expansion, micro-inverters are the way to go. You can start with a small system now and add on to it later without hassle.

Flexible Array Layout

Panels produce the most energy when they face South (directly at the sun), while East- and West-facing panels will lag behind. 

With string inverters, you typically want all panels in a string to face the same direction. If you mix South- and East-facing panels on the same string, the panels facing East will drag the rest of the string down.

Micro-inverters give you more flexibility with the layout of your array. Depending on your roof configuration, you may need to design a system to distribute panels across multiple sections of your roof. With micro-inverters, the output of each panel is isolated, so you can distribute them however you want without sacrificing output.

Suniva 340 watt solar panel array
These panels have been split across different sections of the roof to take advantage of the limited space available.

Meets Module-Level Rapid Shutdown Requirements

Lastly, the IQ7+ is designed to meet Rapid Shutdown requirements outlined in the latest version of the National Electric Code without the need for any additional equipment.

In short, solar systems need to be able to “de-energize” quickly in case of emergency. If a house were to catch fire, the firefighters may need to climb on the roof and cut a hole to ventilate the smoke. In doing so, they could cut through the solar wiring, which is often routed into the attic to run alongside the roof rafters.

As a safety measure, roof-mounted systems need a way to quickly release the live current running through the wires, to prevent the risk of shock for first responders.

The IQ7+ meets Rapid Shutdown requirements by default. For the SMA Sunny Boy, you’d have to add something like the FireRaptor Rapid Shutdown Unit at an additional cost to meet the regulations.

It’s worth noting that this section only applies to roof-mount systems. Ground-mounted systems won’t interfere with first responders who need to work on your roof, so they’re exempt from the Rapid Shutdown requirements.

Disadvantages of Micro-Inverters

More Expensive Up Front

Of course, the flexibility and added features of micro-inverters make them more expensive than traditional string inverters. A system with Enphase IQ7+s will cost around 15-20% more per panel than an equivalent SMA Sunny Boy system.

That higher initial investment is well worth it if you live in harsh climates, where inclement weather can put a damper on production. It also makes sense if your site is shaded by trees or other obstructions. In these cases, micro-inverters will salvage production that would have otherwise been lost, easily offsetting their higher price tag.

But if your system will be built in a location with full sun exposure, a standard string inverter is a perfectly good option. If shading isn’t a concern, the SMA Sunny Boy will perform comparably to a micro-inverter system at a much lower price point.

Higher Odds of Equipment Failure

In the “pros” section, we mentioned that adding a micro-inverter to each panel can isolate equipment failures. Even if a panel malfunctions, the output from the rest of the array won’t be affected.

The flip side is that micro-inverters introduce more potential failure points. If your system has 24 micro-inverters, the odds that a piece of equipment will malfunction go up compared to a system with a single string inverter.

Another point is that micro-inverters may be more challenging to replace for rooftop installations. Since they are attached to your panels, it may be a pain to climb on the roof and replace one in the middle of an array. By comparison, string inverters are always installed at ground level, making them much easier to replace if necessary.

When Are Micro-Inverters the Right Choice?

Micro-inverters are the best option if you need to build your system under less-than-ideal circumstances. If your panels will be shaded, or part of the array will face East/West due to the configuration of your roof, micro-inverters ensure your system produces as much power as possible.

If you have plenty of space to build your array in full exposure to sunlight, a traditional string inverter may be the better bet, as it can perform the same job for 15-20% less money up front.

For more info, check out our reviews of a few inverters we carry:

You can also grab a free copy of our Solar Inverter Guide by clicking below.

Download your free solar inverter guide
16 Frequently Asked Questions About Solar Energy, Answered

16 Frequently Asked Questions About Solar Energy, Answered

As a solar equipment supplier that sells direct to the public, we get 200+ calls a day from people at every experience level, from seasoned solar installers to homeowners exploring the possibility of going solar for the very first time.

Naturally, there are some questions we receive on a daily basis. So for the sake of convenience, we decided to gather the answers to the most common questions we hear in one place.

For each question, we’ll give a (very brief) summary, then link to a resource providing a more detailed explanation if you want to research a particular topic in depth. 

Here are some of the most frequently asked questions about solar energy we receive. We’ve written the answers with newcomers in mind, so you don’t need any prior solar background to follow along.

Basic Questions About Solar

Cost, Financing & Return on Investment

System Design & Product Research

Basic Questions About Solar Energy

What is the difference between grid-tied and off-grid solar?

Grid-tie systems connect to the public utility grid. The grid acts as storage for the energy produced by your panels, which means you don’t need to buy batteries for storage. This saves a ton of money, which is why we always recommend connecting to the grid if you have a choice.

If you don’t have access to power lines at your property, you’ll need an off-grid system with batteries so you can store energy and use it later.

There’s a third system type: grid-tied with energy storage. These systems connect to the grid, but also include batteries for backup power in case of outages.

Learn more: Grid-tied vs. off-grid solar

What are the components that make up a solar energy system?

The main components for grid-tie systems are:

  • Solar panels, to capture energy from the sun
  • An inverter, to convert that energy to a format that can power our appliances
  • Racking, the foundation on which you mount your system

Battery-based systems also require:

Aside from these main components, systems also come bundled with small parts like meters, disconnects, and wires. Browse our system packages for a complete parts list.

How long will my system last?

Solar panels are warrantied for 25 years, so that should be your benchmark for system lifespan. However, you should expect to replace a few other parts along the way:

  • Grid-tie string inverters: 10-15 year warranty
  • Off-grid inverters: 5-10 year warranty
  • Batteries: 1-10 year warranty (varies widely depending on technology and model/manufacturer)

When looking at lifetime cost of ownership, be sure to account for scheduled part replacements along the way.

Can I install solar myself?

Many of our customers choose to install their own system to save money on their project. Some install the racking rails and panels, then bring in an electrician for the final hookup. Others simply source the equipment from us and hire a local contractor to avoid paying markup to a national solar installer.

If you are interested in installing your own system, take a look at the DIY solar timeline to get an overview of the process, or join our free DIY solar workshop for in-depth training and guidance on your project.

If you would like to hire someone to install for you, learn how to hire a solar installer you can trust.

How do I get a permit for my system?

Contact your local AHJ (authority having jurisdiction), the office that oversees new construction in your area, for instructions on how to permit your system. This is typically your local city or county planning office. 

You will also need to contact your utility provider to sign an interconnection agreement that allows you to connect your system to the grid (if applicable).

Download our free Solar Permitting Guide for detailed instructions on how to permit your solar system.

What is net metering?

Your utility’s net metering policy outlines the terms you agree to when you connect to the grid. It dictates the rates you are charged or credited for power bought from or sent into the grid. It also outlines terms like variable time-of-use rates.

Understanding your net metering policy is key to figuring out what kind of return you can get from your investment into solar. Read more about how it works in our net metering guide.

Cost, Financing & Return on Investment Questions

How much does it cost to go solar?

Here are our best “ballpark figures” based on your approach to installation. The average system cost is based on the national average energy usage for American homes (914 kwh/mo.), based on pricing as of October 2019.

  • Self-installed: $1.10-$1.60 per watt / ~$9,500 average system cost
  • Hire local installer: $1.85-$2.60 per watt / ~$15,352 average system cost
  • National installer: $2.50-$3 per watt / ~$18,975 average system cost

These are broad estimates. Prices will vary greatly based on your specific energy needs and usage patterns. Use our solar cost calculator to get a tailored estimate based on your location and usage data.

What tax credits and incentives are available?

The federal government offers a large tax credit for installing solar, which can be used to offset taxes you owe when you file. The credit is currently 30% of your total project costs, including installation, but the value drops after 2019.

Read our introductory guide to the federal solar tax credit, or watch the video above for a brief overview.

You may also be eligible for state and local incentives which provide additional savings on top of the value of the federal tax credit. Be sure to research programs in your area so you don’t miss out on any credits or rebates.

Is solar a smart investment?

Grid-tie solar systems pay for themselves by reducing your monthly electric bill. Grid-tie systems have a 5-10 year payback period depending on factors like local climate, cost of electricity, and approach to installation. Considering panels have a 25-year warranty, there’s plenty of time left over to profit off your investment into your panels.

Off-grid systems cost more because they require batteries, but they may still be a good investment compared to other methods of powering the property (like running a power line or using a gas generator).

Read more: Are solar panels worth it? Let’s do the math.

What financing options are available?

If you cannot buy your system outright, there are a few options to go solar with lower up-front cost:

Personal loan: A lender fronts the money for your system. You own the system and can claim any available incentives. You pay a monthly loan payment with interest to your lender.

Solar lease: A solar installer builds a system on your home. They own the system, so they claim any available incentives. You pay a monthly payment to the installer for the right to use all the power that the system generates.

Solar PPA (power purchasing agreement): Similar to a solar lease, except you pay for the power you use each month (at a rate slightly lower than utility power). The installer still owns the system and claims the incentives.

Learn more on our solar financing page.

Which is better: a solar loan, lease, or PPA (power purchasing agreement)?

Solar loans are preferable to leases and PPAs. Under lease and PPA agreements, the installer owns the system, and you are simply renting it from them. That allows them to claim the 30% federal tax credit and any other incentives, which can deprive you of several thousand dollars worth of value. 

Leases and PPAs are an appealing way to go solar with no up-front cost, but they are worse for the consumer in the long run. It is a much better deal to take out a personal loan, claim the credit and use it to accelerate your payback period. 

Learn more about the true cost of loans, leases and PPAs.

Solar System Design & Product Research Questions

What size system do I need?

Your system size depends on your monthly energy use, as well as site factors like shading, sun hours, panel facing, etc. Our solar calculator is a great way to get an estimate based on your personal usage and location in just a few minutes.

If you would like to learn more about the factors that go into the system design process, check out these guides:

What are the best solar products on the market?

Need help picking products? Take a look at our comparison articles:

What’s the difference between string inverters, micro-inverters, and power optimizers?

Inverters convert the power generated by your panels into a format that can be used by your appliances.

A string inverter allows a group (or a string) of panels to plug into a single input on the inverter. For example, a single string inverter may have 3 strings of 8 panels apiece wired into the inverter unit. This is the most cost-effective option, but they don’t perform as well if your panels are blocked by shade, poor weather, or other obstructions.

Micro-inverters are small units attached to every panel. Each micro-inverter controls the output of a single panel. If one panel’s production drops (due to malfunction or shade, for example), the rest of the panels are not affected.

String inverters with power optimizers combine the benefits of both other types. There is a central inverter unit that pairs with power optimizers which are attached to every panel. The inverter controls the power optimizers individually (like micro-inverters), but the centralized inverter keeps overall costs slightly lower.

Learn more about the pros and cons of string inverters, micro-inverters, and power optimizers.

What are the different types of solar batteries?

Lead-acid batteries are the most cost-effective option, but they require routine maintenance (every month or so) and they have a shorter lifespan.

Lithium-ion batteries are much more expensive up-front, but have a much longer lifespan and are maintenance-free.

Learn the pros and cons of each battery type and evaluate the lifetime ownership cost in this breakdown of lead-acid vs. lithium batteries.

Lead-acid batteries are further divided into a handful of different configurations. Read about the differences between flooded, gel and AGM (absorbent glass mat) batteries

Does solar increase the value of my home?

Yes, studies have shown that solar homes sell for 3-5% more than comparable non-solar homes. One NREL study showed that solar-equipped homes sold for $16,995 more on average. 

So if you want to go solar but aren’t sure whether you’ll stay in your house long enough for the system to pay itself off, you can rest assured that you can recoup most or all of your solar investment when you decide to list your home.

Read our analysis of the study: Do Solar Panels Increase Home Value?

More Solar Questions? Continue Your Research

Still have more questions about the prospect of going solar? Grab a free copy of our Getting Started Guide to get a grasp on the fundamentals.

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Monocrystalline vs. Polycrystalline Solar Panels: Understanding Solar Cell Technology

Monocrystalline vs. Polycrystalline Solar Panels: Understanding Solar Cell Technology

Mono vs. Poly Solar Cells: Quick Facts

  • Monocrystalline solar cells are more efficient because they are cut from a single source of silicon.
  • Polycrystalline solar cells are blended from multiple silicon sources and are slightly less efficient.
  • Thin-film technology costs less than mono or poly panels, but is also less efficient. It is mainly used in large-scale commercial applications.
  • N-Type cells are more resistant to light-induced degradation than P-Type cells.
  • PERC Cells add a reflective layer to give the cell a second oppportunity to absorb light.
  • Half-cut cells improve solar cell efficiency by using smaller ribbons to transport electrical current, which reduces resistance in the circuit.
  • Bifacial solar panels absorb light on both sides of the panel.

Solar manufacturers are constantly testing new technologies to make their panels more efficient.

As a result, solar manufacturing has branched into a wide range of cell technologies. It can be confusing to try to figure out why you should pick one option over the other.

Ever wondered about the difference between monocrystalline vs. polycrystalline solar panels? Or N-type vs. P-type cells? You’re in the right place. This article will give a high-level overview of the major solar cell technologies in play and explain the pros and cons of each.

solar panel guide

Free Solar Panel Guide

Learn More »

Monocrystalline vs. Polycrystalline vs. Thin-Film Solar Panels

The first set of terms describes how solar cells are formed out of raw materials.

Traditional solar cells are made from silicon, a conductive material. The manufacturer shapes raw silicon wafers into uniformly-sized silicon cells.

Solar cells can either be monocrystalline (cut from a single silicon source) or polycrystalline (from multiple sources). Let’s look at the differences between the two options.

Solar cell technology comparison

Monocrystalline Solar Panels

Monocrystalline solar panels contain cells that are cut from a single crystalline silicon ingot. The composition of these cells is purer because each cell is made from a single piece of silicon.

As a result, mono panels are slightly more efficient than poly panels. They also perform better in high heat and lower light environments, which means they will produce closer to their rated output in less than ideal conditions.

However, they cost more to produce and that higher cost is passed on to the buyer. Mono panels are a bit more expensive than poly panels of the same wattage.

The manufacturing process for mono panels is also more wasteful than the alternative. Mono panels are cut from square silicon wafers and the corners are shaved off to make the distinct cell shape shown in the picture below. 

Monocrystalline solar panels have a dark, uniform look.

Lastly, mono panels have a uniform black look because the cells are made from a single piece of silicon. I personally think these look better than poly panels, but obviously, that is just a matter of preference.

Polycrystalline Solar Panels

Polycrystalline solar cells are blended together from multiple pieces of silicon. Smaller bits of silicon are molded and treated to create the solar cell. This process is less wasteful because hardly any raw material is thrown out during manufacturing.

The blended makeup of the cells gives poly panels their iconic blue color. If you look at them up close, you’ll see the texture and color is uneven due to the way the cells are made.

Polycrystalline solar panels are blended from multiple pieces of silicon.

Poly solar panels are slightly less efficient than mono panels due to imperfections in the surface of the solar cells. Of course, they’re cheaper to manufacture which means they cost less for the end user.

Thin Film Solar Panels

The majority of solar panels deployed today are made from either monocrystalline or polycrystalline solar cells.

There is a third type of solar technology, called thin film panels, which are usually deployed for large-scale utility projects and some specialty applications. Thin film panels are created by depositing a thin layer of conductive material onto a backing plate made of glass or plastic.

Thin film panels typically don’t see use in residential installs because they’re much less efficient than mono or poly panels. With roof space at a premium, residential customers go with more traditional crystalline silicon panels to maximize production from the space available to them.

However, thin film technology is less expensive to manufacture, and it becomes a more cost-effective option at a larger scale. For commercial and industrial projects without any space restrictions, the lower efficiency of thin film technology doesn’t really matter. Thin film panels often end up being the most cost-effective option in these situations.

In addition, if you’ve ever seen flexible solar panels on an RV or boat, thin film technology is what makes those possible. 

Because they are (as the name implies) much thinner than a traditional silicon wafer, the thin film can be deposited onto plastic to create flexible solar panels. These panels are especially nice for RVs and mobile use when you might not have a flat surface to mount the panel.

N-Type vs. P-Type Solar Cells

The previous section covers the process by which raw material is formed into silicon wafers.

This section has to do with the process by which those wafers are treated to turn them into a functioning solar cell that can generate an electrical current.

What are P-Type Solar Cells?

P-type cells are usually built with a silicon wafer doped with boron. Since boron has one less electron than silicon, it produces a positively charged cell. 

P-Type Solar Cells

P-type cells are affected by light-induced degradation, which causes an initial drop in output due to light exposure. This has historically been the most common treatment method for solar cells.

What are N-Type Solar Cells?

N-type cells are doped with phosphorus, which has one more electron than silicon, making the cell negatively charged. 

N-Type Solar Cells

N-type cells are immune to boron-oxygen defects, and as a result, they are not affected by light-induced degradation (LID). As you might expect, these are positioned as a premium option because they degrade less over the life of the panel.

Here are a few examples of N-type panels:

Most of the panels we sell use P-type cells, which can degrade a little faster, but still perform well for 30+ years. 

When you consider the lower cost of P-type cells, it typically pays to go with a cheaper module that degrades a little more, as opposed to a substantially more expensive panel with slightly less degradation. But that assessment may change as N-type technology advances and costs drop over time.

Other Differences in Solar Cell Technology

PERC Cells

PERC stands for Passivated Emitter and Rear Cell technology. PERC cells are distinguished by an extra layer of material on the backside of the solar panel, called the passivation layer.

PERC Solar cells

Think of the passivation layer like a mirror. It reflects light that passes through the panel, giving it a second chance to be absorbed by the solar cell. More solar radiation is absorbed by the cell, which results in a higher efficiency panel.

PERC cell technology is gaining traction because the inclusion of the passivation layer doesn’t add huge manufacturing delays or expenses. The efficiency boost more than justifies the extra step in the manufacturing process.

Aleo Solar has a good article that gives more context on the history of PERC technology as well as more technical info about how it works.

Half-Cut Cells

Half-cut cells are exactly what they sound like: solar cells cut in half.

The smaller size of half-cut cells gives them some inherent advantages, mainly (you guessed it) improved efficiency over traditional cells. 

Solar cells transport electrical current through ribbons that connect neighboring cells in a panel. Some of this current is lost due to resistance during transport.

Because half-cut cells are half the size of a traditional cell, they generate half the electrical current. Lower current between cells means less resistance, which ultimately makes the cell more efficient.

In addition, half-cut cells can be more shade-tolerant. When shade falls on a solar cell, it not only reduces the production from that cell, but every other cell connected to it in series as well. 

A traditional solar panel may have 60 solar cells, wired in series. If shade falls on one series of cells, you can lose one-third of that panel’s production.

In contrast, a panel made of half-cut cells would have 120 half-cut cells, wired in series/parallel with two strings of 60 cells. Shade that falls on one string would not affect the output of the other, which minimizes production loss caused by shading issues.

Bifacial Solar Panels

Bifacial solar panels are panels that are treated with conductive material on both sides. They’re designed to take advantage of reflected sunlight that hits the back side of the panel.

Bifacial solar panels

In theory, this sounds like a great idea because you are doubling the conductive surface area of the panel. But in practice, bifacial panels call for a much more expensive mounting setup to get any real benefits from the technology.

The system needs to be mounted in an elevated position so that there is clearance below the array. It also calls for the right reflective material beneath your array, like white rocks below a ground mount or a white roof.

Bifacial panels are significantly more expensive to install, and at this point, the minor efficiency gains don’t do enough to recoup the extra installation costs. Bifacial panels aren’t quite ready for the limelight, though that may change as the technology develops further.

Which Panels Should I Choose For My Project?

You might be feeling some information overload right now. It’s nice to understand the nuances of the manufacturing process, but ultimately there’s one question on everyone’s mind: “which one should I buy?”

Our advice is always this: look at cost-per-watt and go from there.

To make a fair comparison between products, divide the panel cost by its rated wattage. The result tells you how much power you will generate per dollar you spend. For example:

Going with Mission Solar would mean fewer panels in your array, but the overall system will cost more due to the higher cost-per-watt on the panels. (Both of these are mono solar panels. In this case, the price difference is because Mission Solar panels are made in America and Astronergy is imported from overseas.)

Once you evaluate pricing on a level playing field, then consider whether other factors (like cell technology or country of origin) play a factor in your decision.

For more info, check out our free solar panel buying guide linked below.

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Net Metering Guide: How the Utility Credits You For Solar Power

Net Metering Guide: How the Utility Credits You For Solar Power

Net Metering: A Quick Summary

Grid-tie solar system owners receive credit for sending electricity into the public utility grid. They use those credits to offset their energy bill. This agreement is outlined by your utility’s net metering policy, which sets the rates at which interconnected solar customers buy and sell electricity.

When you go solar, you need a way to store the energy generated by your panels. The easiest method is to hook into the utility grid to store energy and save it for later use.

But to do that, you’ll need to agree to terms with the utility company that outline how you are credited and billed for power. These policies are referred to as net metering (or net energy metering) agreements.

Under a net metering agreement, the grid acts as energy storage for the solar homeowner, banking the power they generate so they can use it later. The utility tracks your meter to record your net energy usage (energy consumed minus energy sent to the grid) so they can bill or credit your account based on overall usage.

Net metering agreements benefit both parties. The homeowner has a way to store solar power for later use, and the utility benefits because the extra supply of electricity smooths the power demand curve and prevents outages.

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Each utility company has different terms and conditions, so it’s important to contact them before going solar to figure out how the connection process works. This article covers some of the most common agreements so you know what to expect.

Types of Net Metering Agreements

What is Net Metering?

In broad terms, net metering is an agreement with the utility company that allows you to get credit for solar energy sent into the grid. The utility gives you a credit for the solar electricity you generate, and you can use those credits at any time to draw power from the grid.

The utility monitors the meter on your property to track how much energy you use. If you withdraw more than you produce, you pay the utility for any extra usage.

If you produce more power than you use in a given month, any excess production is credited to your account and rolled over to future months. These credits can be “banked” for periods of low production, meaning credits you earn in August can be used in December when the days are shorter and the weather is worse.

Under most net metering agreements, the utility will reimburse you for excess generation, either through a check or energy credits toward your future bill. However, most utilities pay reimbursements at a wholesale rate (vs. awarding credits at retail rates), so most folks choose to take the credit.

What is a Feed-In Tariff?

Most net metering agreements use one meter to track net energy consumption (energy used minus energy generated from solar) and bill everything at a uniform rate.

Under a feed-in tariff, the utility installs two meters: one for the power you use, one for the power you generate. Each meter is billed at a different rate.

Feed-in Tariffs incentivize solar adoption by making the utility pay higher rates for solar energy sent into the grid.

Feed-in tariffs are typically implemented by local governments to incentivize people to switch to renewable energy sources; the utility pays a premium rate to encourage solar adoption. For example, you might buy power at $0.12/kWh, but sell excess power to the utility at $0.25/kWh.

What is Net Purchase and Sale?

This is essentially the opposite of the feed-in tariff structure. The utility still installs two meters, but they charge electricity at retail rates and buy it from you at reduced wholesale rates.

Under this billing structure, the utility only pays their “avoided cost” for anything you feed into the grid—the cost they would have paid to generate that electricity.

This is not as good a deal for the consumer as the regulated feed-in tariffs, but it’s still decent because you can receive payment for surplus generation.

What is Aggregate Net Metering?

Aggregate net metering allows for multiple meters on a property to be offset by a single solar system.

Let’s say you live on a ranch property with your home, a barn, and a workshop, each with separate meters. Under this agreement, all three meters are counted toward the total net energy use on the property.

This works the same as ‘standard’ net metering. The only difference is that it allows you to track more than one meter on a property.

What is Virtual Net Metering / Community Solar?

Aggregate net metering allows a single customer to offset multiple meters on his or her property.

Virtual net metering differs in that it allows multiple customers to participate in net metering with a shared solar energy system.

Under this policy, shared residences like apartment buildings can build a centralized solar system, with individual tenants metered and billed under their own account.

Similarly, neighborhood residents can build a community solar farm to supply power to multiple homes in the neighborhood. Those who choose to buy into the community solar program receive an ownership stake in the shared system. They would be entitled to credits and/or reimbursement in proportion to their ownership stake in the system.

What are Time-of-Use Rates?

Lastly, your net metering policy may be affected by time-of-use (TOU) rates. Under a TOU policy, the utility charges more for electricity during peak demand periods, when people are home from school and work in the evening.

Where applicable, net metering calculations are affected by TOU rates. Solar generates energy during off-peak hours (when the sun is out during the day), so that production is credited at a lower rate. When you flip on lights in the evening, you are billed a higher rate for usage during peak periods.

The result is that you can generate enough energy to cover your usage and still end up paying a bill, because you pay a higher rate to use energy in the evenings than the rate you are credited for producing during the day.

To counteract this, you can invest in an energy storage system that allows for TOU offset. A small battery bank can store daytime production for use during peak periods. By drawing power from your battery bank (instead of the grid) in the evening, you avoid paying higher rates during peak usage periods and maximize the value of your solar production.

Net Metering Caps and Restrictions

Some utilities have restrictions and caps on their net metering policies. These restrictions are in place to level out supply and demand, and to prevent people from taking advantage of the policies purely for profit motive (since you can make money by selling off surplus energy).

These restrictions may include:

  • System size caps: either a concrete limit (systems up to 1 MW) or a percentage (125% of consumption)
  • Technology restrictions: outdated or inefficient technologies may not be eligible
  • Credit rollover limits: credits can expire and be surrendered to the utility if not used within a certain timeframe
  • Property type: residential, commercial and industrial properties may have different policies
  • Renewable energy source: Aside from solar, net metering policies may apply to wind, hydro, fuel cells, biomass, geothermal, and other renewable energy sources.

Next Step: Understand Your Local Net Metering Policy

Thinking of going solar? Contact your local utility a call and ask about their net metering policies. Many have their policies published online.

They’ll explain how they credit you for solar energy produced, which is important to understand if you want to get the most out of your system.

For more help on permitting and interconnection with the utility, grab a copy of our free solar permitting guide!

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Solar Panel Warranty Guide: How Long Will My System Last?

Solar Panel Warranty Guide: How Long Will My System Last?

Solar panel warranties can be a bit of a headache to understand. They’re split into two categories (performance and workmanship), each with different warranty lengths and areas of coverage.

If your system stops producing the way that it should, it’s not always clear whether you’re covered. Since solar is a big purchase, it’s important to understand how solar warranties work to protect your investment.

For your peace of mind, here’s everything you need to know about how warranties work in the solar industry.

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How Solar Panel Warranties Work

What is a “workmanship warranty?”

The workmanship warranty on your solar panels covers any physical defects that stem from manufacturing errors. Some examples might be:

  • Imperfections in the frame or glass
  • Loose junction boxes
  • Faulty connectors
  • Bad cells or damaged cell connections
  • Defective backsheet

If the panel malfunctions due to a manufacturing defect, that is covered under the workmanship warranty.

What is a “performance warranty?”

The performance warranty guarantees your panels will produce near their rated output over the life of ownership.

Panel production naturally degrades over time, but it happens at a very slow rate—less than 0.5-1% production loss per year. While production loss will occur for any panel, the performance warranty ensures it happens at a reasonable rate.

For example, these Mission Solar panels output 360 watts. The warranty accounts for a 3% drop in production in the first year, then 0.7% every year after that. After 25 years, your panels should still produce 288.72 watts (80.2% of their original 360W rating).

A few premium panel manufacturers like LG offer better warranties (87% after 25 years) because their panels degrade at a slower rate.

The performance warranty ensures your system’s output is reliable and consistent. If a panel’s output suddenly falls off a cliff, it would be covered for replacement under the performance warranty.

Linear vs. Step Warranties

Most companies offer a linear performance warranty. Mission Solar’s guarantee of 0.7% production loss every year is an example of a linear warranty: it progresses at a constant rate year-over-year.

Some manufacturers offer “step warranties” on their panels. Under this warranty structure, the performance guarantee stays at a flat rate and steps down at certain milestones.

For example, certain Astronergy panels are covered at greater than 90% efficiency upon purchase, which steps down to 80% at year 10 and stays there until year 25.

Step warranties offer less coverage for under-performing panels. For example, if your panel is producing at 85% output in year 11 of ownership, you would be entitled to a replacement under a linear warranty, but not under a step warranty.

In general, companies have moved away from step warranties, but you may still find them offered on older modules, so it’s something to look out for.

How Long Do Solar Panel Warranties Last?

Most solar panels come with a 25-year performance warranty. This is the industry standard from Tier 1 manufacturers at the moment.

Workmanship warranties cover a shorter timeframe: Mission Solar and Astronergy offer 10-year workmanship warranties, but that number varies by manufacturer.

When the warranty expires, that doesn’t mean your panels stop working! They’ll still be producing power, albeit at a reduced rate. A 360W Mission Solar panel should still produce 288W after the 25-year warranty is up.

They can still be used to power your appliances, but they’re no longer covered if the production starts to taper off. A study by NREL (National Renewable Energy Laboratory) shows that 4 out of 5 panels outperform their warranty, so it’s likely your system still has some life in it after the 25-year mark.

What Are Third Party Warranties?

25 years is a long time. What happens if you need to put in a warranty claim, but the company that made your panels has gone out of business?

For that, certain manufacturers like SolarWorld offer third-party warranties and other forms of warranty protection. In case of bankruptcy, the warranty transfers to a 3rd party insurer who continues to honor replacements and refunds under the original warranty.

Tier 1 manufacturing companies are quite stable, but a lot can happen in 25 years. This provides an extra layer of protection so you don’t get hung out to dry.

Solar Inverter Warranties

So far, we’ve only covered the warranties on solar panels. But there are other parts of your system covered under their own product warranties.

Panels have the longest warranty of the bunch at 25 years. Inverters and batteries generally have shorter warranties.

Here are the warranties for the inverters we supply:

If you opt for a string inverter like the Sunny Boy or HD-Wave, you should factor at least one inverter replacement into the lifetime cost of ownership.

Most inverter manufacturers offer extended warranty programs to cover these replacements. These cost a little bit extra up front, but it’s cheaper than replacing the inverter out of pocket down the road.

Solar Battery Warranties

Battery warranties are a bit trickier. Flooded lead-acid batteries cost less up front, but have regular maintenance requirements to keep them in working order. These batteries have the shortest warranties, and if you fail to perform regular upkeep, the warranty will be voided.

Sealed lead-acid batteries and lithium batteries cost more, but the maintenance requirements are removed and they have longer warranties to match the higher price tag.

Sample battery warranties:

  • Crown flooded lead-acid batteries: 3 years
  • Fullriver sealed AGM batteries: 7 years
  • Discover lithium batteries: 10 years

Read our in-depth cost comparison of lead-acid vs. lithium batteries.

Another thing to note is that the true lifespan of your batteries can vary greatly depending on the application.

Battery life is measured in charge cycles. The act of discharging your batteries (to power your appliances) and recharging them from your solar panels counts as one cycle. For example, this Fullriver AGM battery has a cycle life of around 1250 cycles at 50% depth of discharge.

In off-grid applications, your battery bank is your primary source of energy. You’ll be cycling it on a regular basis to provide uninterrupted power to your property. With heavy use, you’ll reach the expected cycle life at a much quicker pace.

However, if you’re using batteries as energy storage for a grid-tie property, they’ll see less frequent use—only at certain times of day to offset high time-of-use rates, or as backup power during a grid outage.

Though you might use the same exact battery, it will have a longer lifespan in this application because it is not constantly cycling.

Factors That Can Void Your Warranty

One last word of caution: warranties only cover your equipment when your system is properly designed and cared for.

All warranties carry clauses that essentially boil down to this: “if you use the equipment improperly, we’re not responsible for the damages.”

For example, string inverters have a voltage range in which they can operate safely. Your system must be sized so that panels supply the right amount of voltage to your inverter, a process known as string sizing.

If your panels send too much voltage into the inverter, it can fry your equipment. That damage would not be covered under warranty because the manufacturer would consider you to be at fault.

Learn how we calculate string size here (warning: lots of math ahead).

Similarly, battery banks must be sized properly so that they charge or discharge at a healthy rate. Completely draining lead-acid batteries when you cycle them will reduce their lifespan, another mistake that would not be covered under warranty.

This is where we come in. Our complete solar systems are packaged with these restrictions in mind, so you can be sure you’re getting a system that’s properly sized. If you’d like to put together a custom system, you can also consult with an experienced solar designer to ensure your system is up to code.

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How to Size a Solar System: A Step-By-Step Walkthrough

How to Size a Solar System: A Step-By-Step Walkthrough

Once you have determined that a grid-tie solar system is the best option for your home, we want to help you size the system correctly. This article will teach you how to size a solar system that covers your energy use patterns, without over-sizing your PV array.

The process for sizing off-grid solar systems is different, due to the need to account for battery bank sizing. Click here for advice on how to size your off-grid solar system.

As a system designer, I follow a step-by-step process to size grid-tied systems that work with my client’s project constraints.

The first step is to figure out the main constraints on the project and using those restrictions as the starting point for the design. We can approach the project from one of three angles:

  • Budget constraints: Build a system within your target budget.
  • Space constraints: Build a system that is as space-efficient as possible.
  • Energy offset: Build a system that offsets a certain percentage of your energy usage.

I want to make sure I deliver a system that satisfies my client’s specs, but I also need to account for sizing factors that might not be immediately obvious to them.

Some common stumbling blocks that come up over and over again:

  • Local levels of sun exposure
  • Orientation of the array (facing and tilt angle)
  • Plans for future expansion
  • Product efficiency ratings
  • Natural degradation of performance over the life of the warranty

This article is intended to provide a step-by-step overview of the sizing process for grid-tied solar systems, taking the above restrictions into account.

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Sizing Grid-Tied PV Systems: Getting a Quick Estimate

First, gather the Kilowatt Hours (kWh) usage from your electric bill. We want to have all 12 months available so we can look at peaks and valleys in usage. Energy consumption spikes in the summer and winter with heavy use of your A/C and heating units. A full year of energy consumption data gives us the big-picture overview we need.

We also want to average the data from 12 months of bills to know your average monthly kWh usage. Grid-tied systems tend to overproduce in the summer with peak sun exposure.

If your utility provides a favorable net metering policy, the energy your system generates can be banked with the utility as credit to be used later. Not all utility companies do this; check with your local provider.

Next, we want to look up your sunlight hours per day, through a sun hours chart or the PV Watts Calculator (I will get to this in the next steps).

For a general estimate we can use this simple formula, then fine-tune as we get further into the design:

(Yearly kWh Usage ÷ 365 days ÷ average sun hours) x 1.15 efficiency factor = DC solar array size required.

If the solar array cannot face south, on the preferred angle, we need to adjust the system by adding more solar.

Here is an example. I live in New Mexico where the PV Watts Calculator says I have an average of 6.10 sunlight hours per day. That is a LOT, I know, but that is why I live here. I use 1000 kWh per month, or 12,000 kWh in a year. According to the formula:

(12,000 kWh ÷ 365 days ÷ 6.1 sun hours) x 1.15 = 6.2 kW DC solar system required

Fine-Tuning the Estimated System Design

When I am ready to make a solar system estimate as accurate as possible, I pull up the address on Google Maps. I check to see if I have any viable south facing options for a roof mount.

(Your solar system should point toward the equator, so if you live in the Southern Hemisphere, look for north-facing options instead.)

A roof mount is the simplest and most cost-effective solution. It costs less than other racks. Many times the slope of the roof is already set up for solar gain, and it keeps the solar panels close to the inverter and service panel. This is great for the efficiency and costs less in conduit and wire.

To learn more about the pros and cons of each mount type, read this article: Ground Mount vs. Roof-Mount Racking: What’s the Best Way To Mount My Solar Panels?

Customer Tom M. with his roof mounted system in Albuquerque, NM.

If a roof mount is not an option, I will look into the possibility of a ground mount or pole-mounted solution.

Once we know how much area we have for solar panels, and what angles and directions we will be working with, I get out the PV Watts Calculator and follow these steps.

How to Use the PVWatts Calculator

  1. Enter the address and hit the orange arrow to the right.
  2. Once you are on the System Info page, enter the DC system size from the previous section.
  3. Choose standard module.
  4. For array type, select “fixed” for roof mounts, or “open” for ground mounts.
  5. Leave the system losses at around 15%.
  6. Enter the slope of your roof in degrees, and the azimuth. Azimuth is the degrees relating to north and south, with north being zero and south being 180. (Click here to learn how to fine-tune your angle and azimuth values.)

Once all the info has been entered, click the arrow to the right and it will tell you how much power your system will put out on a monthly basis.

This is our step-by-step process for honing in on an accurately sized system. We provide this info because our audience is heavily inclined to DIY, and most people prefer to research at their own pace.

Once you’re ready, we do encourage you to schedule a free design consultation with us so that we can double check your sizing, find compatible products, and ensure the system works within your constraints (budget, build space and energy offset). You can also give us a call at 1-800-472-1142 for an immediate consultation.

Choosing Grid-Tie Solar Equipment

Once we know how big the solar system needs to be, we will cross-reference that with the amount of space available. If you are doing a ground mount, that is usually not a problem.

From my example above, I know I need a 6.2 kW DC system. I can multiply this number by 1,000 to confirm that I need 6,200 watts of solar panels.

My fastest resource is to go to our grid-tied solar packages and scroll down until I see something in this range. If the client expresses a desire to buy American-made panels, or needs certain features like individual panel monitoring, I take those choices into account.

Here are a few viable options I’d consider. Note that the imported panels are more cost-effective, so you get roughly 10% more production for the same price.

Grid-tie systems with American-made panels:

  • 6.2 kW system with 310W Mission Solar panels and SolarEdge Inverter / optimizers
  • 6.2 kW system with 310W Mission Solar panels and Enphase IQ7+ micro-inverters
  • 6.2 kW system with 310W Mission Solar panels and SMA central inverter

Grid-tie systems with imported panels:

  • 6.7 kW system with 335W Astronergy solar panels and SolarEdge inverter / optimizers
  • 6.7 kW system with 335W Astronergy solar panels and Enphase IQ7+ micro-inverters
  • 6.7 kW system with 335W Astronergy solar panels and SMA central inverter

If you’re having trouble deciding which products to buy, we’ve written articles covering that ground as well:

Of course, sometimes it’s easier to talk to someone with experience and have them walk you through the design process. The fastest way to get a thorough evaluation of your solar needs is to call us at 1-800-472-1142 and connect with one of our designers. We’d love to help you design the perfect grid-tied system for your needs.

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Pros and Cons of Solar Power

Pros and Cons of Solar Power

We’re huge advocates for solar energy, but we recognize it isn’t the right solution for everyone. While solar is sustainable and ultimately cheaper than utility power in the long run, it also requires a significant up-front investment and doesn’t work for every property / roof type.

The ultimate question is whether the advantages of solar power outweigh the disadvantages. In this article, we’ll present the pros and cons of solar energy so that you can decide if going solar makes sense for you.

Advantages of Solar Power

  • Energy independence
  • Eliminate electric bill
  • Profitable investment
  • Strong government incentives
  • Sustainable
  • Low maintenance
  • Improves property value

Disadvantages of Solar Power

  • Expensive up front
  • Takes up space
  • Energy storage is expensive
  • Not right for every property
  • Makes less sense if you rent

Advantages of Solar Energy

1. Energy independence

Traditionally, most people depend on the utility company to supply them with power. When the grid goes down, going without power for an extended period of time can be a helpless feeling.

If you own a solar system with energy storage, you can keep generating power during emergencies. That peace of mind is invaluable if you live in a place with an unreliable power grid, or are regularly threatened by severe weather conditions like tornadoes and hurricanes.

Utility power also restricts people who want to live off the grid, like a remote hunting cabin. Solar can generate energy where it would be too expensive to run power lines.

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It’s liberating to have complete control over where and how you produce energy. And with electricity costs rising, it also feels great to lock in a fixed rate for your electricity over the next few decades.

2. Eliminate your electric bill

Who doesn’t love one less bill coming out of their paycheck? With a properly sized system, you can drastically reduce or completely eliminate your electric bill.

Even if you extend your payback period by taking out a loan to finance your project, you still enjoy reduced electricity costs from the moment you flip the switch on your PV system.

This is the most exciting part of solar for many people: bringing the system online and watching their power bill disappear.

3. (Grid-tied) solar is a profitable investment

If you buy a grid-tie system (the type of system you build if you have access to power lines), you can expect your investment into solar to turn a profit in the long run.

Assuming the national average for cost of electricity, it would take about 6.08 years to recoup your investment into a $10,000 system. Beyond that point, you start to generate a profit from your system.

In fact, over the 25-year life of the solar panel warranty, we estimate you would earn $31,031 on energy bills after clearing the initial payback period.

4. Lucrative government incentives

The investment into solar becomes even more appealing when you take government incentives into account. State and federal programs are in place to encourage people to invest in renewable energy. Claiming these can put a ton of cash back in your pocket.

The main incentive is the 30% federal tax credit for going solar. Under this program, you are eligible to receive 30% of the total installed cost of your system as a tax credit at the end of the year.

This credit is a dollar-for-dollar reduction of your tax liability. Every dollar in credit is a dollar less that you pay in taxes at the end of the year. So if you buy a $10,000 system and receive a $3,000 credit, you will owe $3,000 less in taxes at the end of the year.

While the federal tax credit is the largest solar incentive, don’t skip out on local incentives, either. Depending on where you live, certain jurisdictions offer local incentives that can be claimed in addition to the federal credit.

5. Sustainability

A sustainable energy source is one that we can use without depleting the source of power. Oil and gas are not sustainable, because we consume those resources as we use them.

In contrast, solar is sustainable because the source of energy (sunlight) is constantly replenished. We can use solar energy without worrying about whether we will deplete the Earth’s natural resources for future generations.

6. Low maintenance

Solar systems don’t have a lot of moving parts. As a result, they rarely break down or require maintenance to keep them running optimally.

Panels are warrantied to last 25 years, but many have a much longer lifespan. (See our article “How Long Do Solar Panels Last?” for a study on the true lifespan of panels.) You rarely, if ever, need to fix or replace panels.

It’s common to replace your inverter at least once over the life of your system, as inverters are typically warrantied for 10-15 years. But that’s about the only scheduled maintenance you will encounter for grid-tied systems.

Off-grid systems are a bit more complex because they must include batteries, which often require routine maintenance. Specifically, flooded lead-acid batteries (the cheapest option available) must be checked and refilled with water regularly to keep them functioning properly.

However, building a grid-tied system eliminates the need for batteries, so most people will rarely need to check in on their system for maintenance or replacements.

7. Improves property value

Studies of the real estate market have proven that homes equipped with a solar power system sell for more than their non-solar counterparts.

In fact, the Lawrence Berkeley National Library conducted research that shows that solar homes fetch an extra $14,329 on average, a 3.74% increase over non-solar homes.

It’s no question that solar power systems substantially increase property value. Home buyers see solar as a major selling point, and they’re willing to pay a premium to move into a solar-powered home.

Disadvantages of Solar Energy

1. It’s expensive to get started

Solar is expensive – at least up front. To build a system that would power the average American home (which uses 897 kWh of electricity every month), you might pay $8,000-$10,000 depending on the products you choose.

That doesn’t include the cost of shipping or installation.

Of course, you’re paying for at least 25 years of energy production up front. In the long term, you break even on the investment and start to make money, but that doesn’t change the fact that not everyone has thousands of dollars in their pocket to get their solar dreams off the ground.

The up-front cost is the main barrier to going solar. Financing options are available, and the payback period is quite favorable even when you take interest into account. However, not everyone wants to be on the hook for loan payments.

2. It takes up a lot of space

Standard solar panels measure 39” wide by either 66” to 72” tall (for 60-cell and 72-cell panels, respectively).

To offset the national average of 897 kWh of electricity per month, you’d need at least 24 panels. In an 8×3 configuration, that system will be 26 feet wide by 44 feet tall. That’s going to take up a lot of room on your roof or in your yard.

Most people opt for a roof mount because it takes advantage of space that would otherwise go unused. If you need to design around odd angles and obstructions, you can always split the panels into sub-arrays, like our customer Luis did when he built his system:

Wholesale Solar customer Luis split his system into sub-arrays to work around the shape of his roof. We featured it as our Install of the Month in September 2018.

3. Energy storage is expensive.

Batteries are the single most expensive component to a solar power system. Not all systems require batteries, but they become mandatory when you go off the grid. They are also required if you need to supply backup power to your grid-tied property.

(Grid-tied systems don’t automatically provide backup power during outages. That’s a common misconception. For backup power, you need a grid-tie system with energy storage – essentially, a battery designed to work with grid-based systems.)

Expect to pay a lot more money when you add batteries to a system. Battery banks cost at least a few thousand dollars, and if you buy high-end lithium batteries for a full-scale off-grid system, that’s easily a 5 figure investment into the batteries alone.

Furthermore, batteries don’t last as long as the other parts of your system. Lead-acid battery warranties range from 1 to 7 years, meaning you’ll replace them 4 or 5 times before the panel warranty is up.

Lithium batteries justify their high price tag by lasting 10-15 years, but you’re still in for at least one replacement over the life of your system.

4. It’s not right for every property

Not every property is a good fit for solar power.

Some properties are simply too cramped to find any space to build a system. Others are covered in shade and wouldn’t get the sunlight required to generate enough energy.

While there are technologies like shade optimizers and custom racking to mitigate these concerns, they only accomplish so much. If you don’t have anywhere to put your panels, it’s going to be a real challenge to make solar work for your home.

5. It’s better if you own your home (and won’t be moving for a while)

Solar can be a profitable investment, but the payback math assumes you’ll be living in the same property for the full duration of the 25-year warranty.

It takes several years to break even on the initial cost of the system before you start to pocket the savings from your energy bill. Solar makes a lot less sense if you don’t own your home, or have the urge to move within the next few years.

The good news is that because solar increases property values, you are likely to recoup your investment into the system when you go to sell your home. But most people who go solar do it because they want to be self-sufficient and generate their own (less expensive) electricity for the next few decades.

Think about whether you’ll stick around for a while in your current property before you make the long-term investment into solar.

Questions? Consult with a solar expert.

Still not sure if the advantages of solar outweigh the disadvantages? You can always schedule a consultation with one of our expert design techs. We’ll answer questions, clear any design hurdles, and help you decide if solar is right for you.

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Grid-tied vs. off-grid solar: are you sure you want to live off the grid?

Grid-tied vs. off-grid solar: are you sure you want to live off the grid?

Let’s clear up one of the most common misconceptions in the solar industry: the idea that you must go “off the grid” to go solar.

This article will explain the different types of solar power systems: grid-tied vs. off-grid.

Many people call us looking for help going “off the grid.” But when we explore their motivations a bit more, we find that what they actually want is to ditch their utility company.

Really, they want to go solar to be independent, generate their own power, and stop paying money to the utility every month.

If this sounds like you, read on. Because you can accomplish all these things without going off the grid. It’s called grid-tied solar, and it’s the preferred type of solar system for any property that has access to power lines.

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Why? Because it’s cheaper. No, really, it’s a lot cheaper. You should always build a grid-tied system when you have the option to do so.

Let me explain why.

Grid-tied vs. off-grid: what do these terms really mean?

The difference between grid-tied and off-grid solar revolves around where you store the energy you generate.

Every system needs a place to store energy so that it can be used on demand. Your panels only generate charge when the sun is out during the day, but you still need a way to turn the lights on in the evening.

With grid-tied systems, the energy you generate is sent into the utility grid. Your panels feed electricity into the grid, which can be distributed to other people in your area.

In return, you receive a credit for the energy you generate, which you can use any time. Think of it like a transaction at the bank: you are allowed to withdraw as much as you deposit. This is what allows you to keep the power on when the sun goes down.

Off-grid systems are different. With no access to the utility grid, you must find another solution to store energy.

For that, you’ll need to add a battery bank to your system. Batteries provide dedicated energy storage. Without any access to power lines, batteries are mandatory for off-grid solar systems.

In summary: grid-tied systems store energy in the power grid, while off-grid systems store energy in batteries.

When in Doubt, Go Grid-Tied

It doesn’t cost anything extra to store electricity in the grid. But adding batteries to an off-grid system is a significant extra cost.

In fact, batteries are the most expensive part of a solar system. They represent as much as 30-40% of the cost of an off-grid system.

Batteries alone are a 4-5 figure investment. For that simple reason, we always recommend connecting a grid-tied system if you have the option.

Why spend thousands of dollars on batteries if you don’t need them?

Browse grid-tied system packages in our shop.

What about Energy Storage Systems?

Right now you might be thinking, “what if I’m connected to the grid but still need energy storage?”

For that, there’s a third system type. It’s called grid-tied with battery backup (a.k.a. energy storage systems).

These systems connect and store energy in the grid, but they also include batteries. There are two reasons you might want to add energy storage to a grid-tied system:

  • Store backup power in case of outages (useful if you live in an area with an unreliable power grid or severe weather)
  • Store energy so you can use it or sell it later (useful if you live in an area with a certain utility billing structure, such as time of use rates, high demand charges, or no net metering)

The same caveats apply: batteries aren’t cheap, and adding them to your grid-tie system lengthens your payback period. But in some places, it’s invaluable to add security against harsh weather, outages, and inflated electricity costs.

Energy storage systems provide extra peace of mind and help you get the most out of the electricity you generate. It’s up to you to decide if it’s worth it to spend more on your system for the added flexibility.

Browse grid-tied systems with battery backup in our shop.

Continue Your Research

Have any more questions about the process of going solar? Check out our Getting Started Guide, a crash course on the basics of designing and installing your solar energy system.

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What is a kilowatt hour?

What is a kilowatt hour?

Kilowatt hours measure energy usage and production.

If you’re thinking about going solar (or just want some advice on how to reduce your energy consumption), you’ve probably come across the term kilowatt-hours.

But exactly what is a kilowatt hour? And why do we need to know how many we use each month?

First things first: What is a kilowatt hour?

A kilowatt-hour (kWh) is a measure of how much energy you use over a set period of time. It determines how much you pay for electricity each month, since the utility company bills you on a cost-per-kWh basis.

Here’s how it works.

Every appliance has a rating which measures how many watts of power it uses. For example, an oven may be rated at 2000 watts, or 2 kilowatts. (1 kilowatt equals 1000 watts.)

If you cook something in that oven for 30 minutes, here’s how to calculate the total energy used:

2 kilowatts x 0.5 hours = 1 kilowatt-hour (kWh) of energy used.

To determine how many kilowatt-hours an appliance uses, simply estimate how long you use it each day, then multiply by the wattage rating.

Easy so far. But how can you use this information?

Measuring Electricity Cost Per kWh

Utility providers track your usage with a meter and bill you based on total kilowatt-hours consumed.

In America, the average cost of electricity is about 12 cents per kWh. However, that can fluctuate based on where you live as well as what time of day you use the electricity.

Many utility providers bill variable rates for Time of Use (called TOU rates). If you are familiar with the concept of surge pricing, that’s what this is: electricity costs more when lots of people are using it.

There’s less demand during the day, so the rate is lower. When people come home from school and work, the rate goes up because the demand is higher.

You can usually find the breakdown of TOU rates on your utility provider’s website, or right on the electric bill.

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But it might be quicker to measure how those costs average out based on your usage patterns. Divide your monthly payment by your total kWh usage to get your average cost of electricity:

$130 electric bill / 1,237 kWh used = 10.51 cents per kWh

How Kilowatt Hours Factor into Solar System Sizing

Understanding kilowatt hours is key to being able to design a system that works. Without that information, your system might be too small to cover your entire energy bill (or too large, in which case you’re just throwing money away and diluting the value of your investment).

So we use your kilowatt-hour usage as the starting point in the system design process. Once you know how much energy you use, you can size your system components to match usage demands.

Our solar cost calculator can provide a ballpark system size and cost based on your kWh usage. You can also read about the math behind this formula in full detail in our article: “How Many Solar Panels Do I Need?”

To get an accurate calculation, there are a few things to take into account:

  • Average monthly usage
  • Peak usage (it will spike when it’s snowing or 100 degrees outside)
  • Future changes in energy usage patterns

Your system should be sized to cover you year-round. Make sure to take a year’s worth of usage into account, since freezing winters and 100+ degree summers tend to skew the usage data.

Also, carefully consider whether your usage will increase in the future. If you plan to have kids, build a new shed on your property, or buy an electric vehicle, those things will eat up a lot more energy and your kWh usage will climb.

You don’t need to build for future usage now, but it helps to plan your system with expansion in mind. Certain pieces of equipment are designed to facilitate expansion, like microinverters and lithium batteries.

Read more: Best Grid-Tie Solar Inverters >> | Best Solar Batteries >>

Why Kilowatt Hour Usage Is So Important For Off-Grid properties

When you’re connected to power lines, finding all this information is simple. Just grab your latest electric bill. Your provider prints your kWh usage on your bill every month, and some list their cost-per-kWh rates as well.

This makes it easy to do the math on system size. You can also drop the number into our solar cost calculator for a quick ballpark cost and sizing estimate.

Off-grid systems are different.

When you go off the grid, you likely won’t have a precedent to figure out how much energy you will use. Instead, you’ll need to fill out a load evaluation sheet, listing each appliance manually and estimating how much you will use them each day.

Daily kWh usage is crucial to building a system that can supply uninterrupted power to your off-grid property.

You don’t want to look at your yearly usage, but rather your needs on a day-to-day basis. The goal is to store enough power to cover yourself if any problems arise (like severe weather or equipment failure).

People tend to store about a day’s worth of power in their battery bank, and lean on a generator for backup. But you can plan for more cushion with your battery bank if you want the extra peace of mind.

To estimate daily usage, find the kWh usage (wattage x hours in use each day) for every large appliance in your off-grid home and add them all together.

The total is your daily usage, which can be used as the basis to size your system:

Daily kWh Usage ÷ Sun-Hours ÷ 0.9 (inefficiency factor) = Minimum Solar Array Output

How to Estimate Solar Cost Based on Kilowatt Hour Usage

Got your kWh usage on hand? Plug that info into our solar cost calculator to see how much it might cost you to go solar.

Grid-tied systems tend to pay for themselves quickly. It’s reasonable to expect to break even on your investment within 5 years.

Off-grid systems cost more and come with different expectations. Unlike grid-tie systems, the value in off-grid systems isn’t necessarily making a profit from your investment.

Instead, it should be viewed as a means to generate energy where there is no access to power lines. To determine whether off-grid solar is the right choice, you should compare it against the cost of other methods to generate power, like wind turbines or gas generators.

Interested in solar, but not quite sure where to start? Download our Getting Started Guide to get up to speed with the essentials.

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