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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.

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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.

Download our free solar panel buying guide!
Install of the Month – June 2019 (Part 2)

Install of the Month – June 2019 (Part 2)

Every month, we highlight our favorite customer projects in our Install of the Month feature. These galleries give our visitors an idea of what to expect from the DIY solar process.

Worked with us to build a system and want to show it off? Submit your install for a chance to have your system featured on our blog! We’ll send a WSS care package your way if we feature your project.

We featured an Install of the Month winner earlier this June, but this system built by Jerry R. was too good to pass up. So we’re back for round two!

Jerry’s project stands out thanks to knowledge and commitment to the DIY approach. He’s done quite a bit of DIY work in the past and was eager to tackle this solar build as his next project.

Along the way, he even built a trolley to help him lift panels on to the roof—a solution he custom designed and built exclusively for this project. Alden, his design consultant, was impressed by his ingenuity and enthusiasm throughout the process. So were the inspectors, who gave Jerry high marks for his professional craftsmanship when they signed off on the build.

Jerry was eager to share his experience going solar, so we’ll let him take it from here!

What solar system type did you install?


Did you have any previous DIY experience?

I have a ton of DIY experience. I have installed a 16 KW Generac Standby generator, a complete 16 zone 70 head underground sprinkler system, a complete kitchen addition from the ground (I mean foundation) up, an On-Demand Water heater, zoned HVAC control, a Smart Home system and an electric car charging station to name a few. I have completed all of these projects 99% by myself… electrical, plumbing, framing, sheetrock, you name it, I’ve done it. Even with all that, this is the first time I was up on my roof for an extended period of time… and I am not great with heights.

What was the most difficult part of the installation?

Getting the first rail just right. The roofer had done a really lousy job of installing the shingles so there was not a straight line to be had. This made installing the FlashFoot 2 a challenge. I devised a means of determining distance and square to overcome this. I took about 4 hours to install the first 42 foot rail and only about 1.5 hours once I got to the fourth 42 foot rail. I chose to do all of the splicing in place. You can’t carry a 42 foot rail by yourself and not break something.

The other difficult part was panel lifting and installation. For this I designed and built a trolley (see pictures). The trolley was designed to work with a standard extension ladder. I used a double pulley system and casters that would ride on the ladder sides to reduce friction. One person could easily lift a 40 lb panel to as high as the ladder will go. With this trolley and the help of two neighborhood kids we were able to install 31 panels in about 6 hours.

How many helpers did you have?

I did all of the work myself except for the actual panel installation. I had two helpers for that… one on the ground using the self designed trolley to move and lift the panels, and one on the roof with me to install the panels. That worked very well. The first one took us about 45 minutes to get the process right. The last 5 took us only 8 minutes each. I guess we learned something…

Did you hire a contractor?


Were there any unforeseen additional parts or tools you needed?

Safety harness, shingle lifter, trolley parts, knee pads.

How long was the full installation process?

I did everything myself so I took my time.
  • Permitting: 5 days
  • Material Receipt Panels May 2, 2019
  • Material Receipt Remainder: May 6, 2019
  • Combiner 3 and Disconnect installation: 16 hours
  • Line side taps and Transfer Switch panel work: 6 hours
  • 1″ Main Trunk (75′) and wire pull (8 #10 plus ground): 24 hours
  • Garage roof rails: 10 hours
  • Main roof rails: 21 hours
  • Four #10 branch circuits: 40 hours
  • 31 Microinverter installation: 3 hours
  • 31 Solar Panel installation: 6 hours
  • Commissioning: 3 hours (including Enphase setup)
  • Inspections: 3 hours
  • Project Complete: May 30, 2019

How did it feel to get your solar project finished?

Well, I was very happy… first that it was done and second, how nice it looked. All of the inspectors commented on the quality of the workmanship. Now I am looking forward to many years of clean, reliable solar power.

Who else did you consider before choosing Wholesale Solar?

I considered a number of turn-key installers but felt I could do this myself. I found Wholesale Solar on-line. I was skeptical but Alden Silber was my rock. He was with me through the whole process and I am very grateful for his guidance and assistance.

What were your total solar install costs? (Your best ballpark estimate)


How much did you save on your taxes?

I hope to save about $9,000 this year on my taxes.

Components in Jerry’s system:

Jerry's Solar Breakdown:

  • System Cost: $28,952 including installation
  • Yearly System Output: 13,455 kWh per year
  • Federal Tax Incentive: Qualifies for $8,685 U.S. Federal Tax Credit
  • Utility Rates: 14.9 cents/kWh

It’s Your Turn

Thinking about making the switch to solar? Download our Getting Started Guide. We’ll walk you through everything you need to know about buying a solar energy system that covers your needs.

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“Free Solar Panels” Are a Bad Deal. Here’s Why.

“Free Solar Panels” Are a Bad Deal. Here’s Why.

Ever seen a solar company promote an offer for “free solar panels?”

The offer sounds too good to be true…and unfortunately, it is.

Yes, there are (legitimate) installers that will put free solar panels for your home. But the catch is that they require you to enter into a solar lease or power purchasing agreement (PPA).

These offers entice people with a no-cost way to go solar. But when you examine the contracts, they heavily favor the solar installer over the 25-year life of the system.

This article explains the economics behind leases and PPAs to show how the offer of “free solar panels” ultimately costs the end user money in the long run.

What are Solar Leases / Solar PPAs?

Solar leases and PPAs offer people a way to go solar with no up-front cost.

Under a solar lease, the installer builds a system on your property and charges you a monthly fee to lease the equipment from them. You pay a flat monthly fee and get to use 100% of your system’s production.

Power purchasing agreements (solar PPAs) are similar, except instead of renting the equipment for a set fee each month, you buy power from the installer at a flat rate per kWh. So if you use less power than your system produces, you don’t have to pay for any excess generation.

Drawbacks of Solar Leases & Solar PPAs: “Free Solar Panels” Aren’t Free

Under both agreements, the main drawback is that you don’t own your system. The installer owns it.

They structure it this way so that they can claim the Federal Tax Credit and any local incentives for going solar. As of 2019, that represents a 30% credit on your total costs to go solar.

A system that costs $10k rewards a $3k tax credit to the system owner. Under leases and PPAs, it is the installer—not you—who gets to pocket this credit. You miss out on the largest financial incentive for supporting renewable energy.

solar guide

Free Federal Tax Credit Guide

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Yes, they’ll put free solar panels on your roof, but they also reap most of the long-term value from owning the system. They make more than enough profit over the life of the system to recoup the cost of equipment—savings that should end up in your pocket.

A Better Way To Finance Your System

Of course, we understand why leases and PPAs are appealing. You get the benefits of going solar immediately, like making a positive impact on the environment and locking in a flat electric rate for the next 25 years.

Leases and PPAs let you enjoy the benefits of going solar without the up-front cost. But there’s another financing option that gives you a much better return on investment: a personal loan from your bank or another 3rd-party lender.

Solar leases and PPAs are essentially high-interest-rate loans from a solar installer. You tend to get better rates and terms from your bank, especially if you’ve been a long-time customer.

But the major distinction is that by taking out a personal loan, you are the owner of your system. This allows you to claim the 30% tax credit for going solar—which can immediately be applied to your loan balance to accelerate the payback schedule, if you so choose. (Check out the video below if you want to know more about how the tax credit works.)

The Hidden Cost of “Free Solar Panels”

So how does buying solar stack up to leases and PPAs?

We did some math to figure out the return on investment into solar under four different payment plans:

  • cash purchase
  • personal loan
  • solar lease
  • solar PPA

Our math is based on the cost to own this 5.2 kW system under each of the four payment plans. We assume the cost of electricity starts at $0.16/kWh and raises by 3% each year for 25 years (the length of a solar panel warranty).

For the purchase and personal loan options, the value of the 30% tax credit is included because you own your system. We also factor in a $1/watt installation charge for these options.

For leases and PPAs, we did not add the installation charge because it is included as part of the package. We also leave out the tax credit, because that belongs to the solar company that owns the system.

See how all four payment plans stack up over 25 years:

As you can see, buying your system outright represents the best value over 25 years, even though the cash payment puts you in the red up front.

The next best option is taking out a personal loan. The initial cost is $0, but interest payments eat into energy savings for the first 7 years until the loan is paid off. It quickly rebounds after year 7 when the owner starts to keep 100% of the energy savings from their system.

After that, we come to solar leases and solar PPAs. Though they don’t cost you anything up front, the value is dampened by the solar company taking a cut of the savings each month. By the end of the warranty period, leases and PPAs have chewed up more than half the potential energy savings as profits for the solar installer.

This is why we strongly recommend choosing a personal loan over a solar lease or PPA If the option is available to you. An offer of “free solar panels” may be tempting, but it could potentially cost you $25K in energy savings over the life of the system.

We want everyone to go solar—but we also want them to fully reap the benefits. If you need to finance your system, personal loans are by far the superior option to solar leases or PPAs.

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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.

solar guide

Free Solar Permitting Guide

Learn More »

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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Install of the Month – June 2019

Install of the Month – June 2019

Every month, we highlight our favorite customer projects in our Install of the Month feature. These galleries give our visitors an idea of what to expect from the DIY solar process.

Worked with us to build a system and want to show it off? Submit your install for a chance to have your system featured on our blog! We’ll send a WSS care package your way if we feature your project.

This month’s winner is Michael from Davidson, NC. As a carpenter and engineer, taking on a DIY solar build was right in his wheelhouse. 

Although the heat delayed the installation somewhat, they still managed to wrap up the project in less than 10 days. When all was said and done, they built a system that will offset over $1,500 in electric bills every year.

We connected with Michael to ask some questions about how the project went. He was kind enough to pass along this time-lapse video of the entire project from start to finish, which gives a great snapshot of what to expect from the DIY solar process:

What solar system type did you install?


Did you have any previous DIY experience?

I am a carpenter, engineer and seasoned DIY’er.

Before moving back to NC we renovated a 90 year old Colonial in Hartford Connecticut including all new electrics. Installing a Solar System seemed to be much more fun than replacing knob and tube!

What was the most difficult part of the installation?

The installation itself was not difficult. It helped to prepare by watching the videos and the material available from WS and SolarEdge online. The heat, however, became a difficult factor limiting the work time on the roof to the mornings. I feel we maximized our time by working inside to install the inverter, wiring the switches and panel etc., when it got too hot on the roof.

The most difficult process overall was the permitting prior to installation. There were simply no clear directions on what the process is for a homeowner functioning as the general contractor. It was a “learn as you go” experience for us and with a few more clear directions a lot of time and resources could have been saved.

How many helpers did you have?

My father, an electrical engineer, joined me from Germany and was a great helper. My wonderful wife Alison made a lot of phone calls during the permitting. Our 3 daughters provided a lot of moral support and served Gatorade during the installation.

Did you hire a contractor?

NO -the only trade we had to contract was a structural engineering analysis of our roof structure, which was required for the permit.

Were there any unforeseen additional parts or tools you needed?

We decided during the preparation to buy some 2 by 4’s and OSB boards for scaffolding to make the installation easier and safer. This is due to our 45 degree roof angle.

How long was the full installation process?

It took 7 days to install the system. It took 1.5 days to build and remove the scaffolding.

How did it feel to get your solar project finished?

GREAT! It really all went very smoothly and better than expected. Seeing the first production number in the APP was amazing! Obviously we check it every day since.

One goal for this project was to show our children that the sun can produce our own energy, which can greatly impact the future of our planet. The fact that our 5 year old Josie now points out potential good solar roofs as we drive through our town is simply the feeling of great accomplishment!

Who else did you consider before choosing Wholesale Solar?

In preparation for this project we read some literature and checked out several online retailers. The fact that WS offers different pre-configured packages triggered the call to discuss our desired system in more detail.

After the first call with Wil there was no question that we wanted to work with WS. The very competitive pricing combined with the technical expertise and helpfulness was what we were looking for.

What were your total solar install costs? (Your best ballpark estimate)


How much did you save on your taxes?


Components in Michael’s system:

Michael's Solar Breakdown:

  • System Cost: $16,500 including installation
  • Yearly System Output: 14,722 kWh per year
  • Federal Tax Incentive: Qualifies for $4,950 U.S. Federal Tax Credit
  • Utility Rates: 10.24 cents/kWh

It’s Your Turn

Thinking about making the switch to solar? Download our Getting Started Guide. We’ll walk you through everything you need to know about buying a solar energy system that covers your needs.

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Can Solar Energy Storage Be Claimed Under the Federal Tax Credit?

Can Solar Energy Storage Be Claimed Under the Federal Tax Credit?

Solar + Storage and the Federal Tax Credit

This month, House representative Mike Doyle introduced a bill to expand the federal tax credit for solar systems with energy storage. Under the new bill, all energy storage products would become eligible to be claimed under the tax credit.

The federal tax credit is a major incentive for going solar. Under the program, 30% of your project costs can be claimed as a credit to reduce your tax liability when you file your federal taxes.

But right now, the cost of energy storage can’t always be claimed under the credit. That would change with this new bill, which would remove restrictions and make all storage products eligible to get full value out of the credit.

As solar batteries become more affordable, energy storage adoption is on the rise. Sunrun reports that 20% of new solar systems installed in California in 2018 included an energy storage solution. If this legislation passes, it will accelerate solar+storage adoption by simplifying the process of claiming the credit.

solar battery guide

Free Solar Battery Guide

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Why Invest in Solar + Storage?

Grid-tie systems connect to the public utility grid. When your panels generate energy, the electricity feeds into the utility grid. The utility credits your account for the electricity you contribute, which you can draw upon during low sunlight periods (at night, during bad weather, etc.).

Batteries aren’t necessary for grid-tie systems, but they add versatility to your application.

The main appeal is the ability to store energy and use it during peak periods. Your panels generate energy during the day when the sun is out, but most utilities charge much higher rates during peak usage periods (around 5-10pm, when people come home from work and school). Batteries allow you to store energy generated during the day for use during the evening, bypassing peak usage rates and saving you money.

Batteries also offer emergency backup when the power grid goes down. Since the solar array is tied to the utility grid, it needs to stop sending power into the grid during outages. This anti-islanding feature protects utility workers who are making repairs to the grid. With an energy storage system, your batteries will take over during outages, acting as a backup power source when the grid goes down.

How Solar + Storage Works Under the Current Tax Credit Law

Under the current law, energy storage solutions can only be claimed under the tax credit if they are charged by a renewable energy source (like solar). If you charge the batteries with grid power, that’s not a use case that is eligible for the incentive.

The amount you can claim is proportional to how often the battery is recharged from a renewable source. If you are charging your batteries from solar 90% of the time, you can claim 90% of the cost of the battery under the credit.

For example, here’s the math for a $5,000 battery bank that receives 90% of its charge from solar:

$5,000 x 0.9 (90% solar charge rate) x 0.3 (30% tax credit) = $1,350 tax credit

Furthermore, if you spend more than 25% of your time charging batteries from the grid, you can’t claim your batteries under credit at all. You must hit a minimum of 75% PV charging rate to be eligible:

  • Battery charged by PV under 75% of the time: not eligible to claim tax credit
  • Battery charged by PV 75-99% of the time: claim a portion of the tax credit equal to PV charging rate
  • Battery charged by PV 100% of the time: claim the full tax credit

Take a look at this 1-page fact-sheet from NREL for more info.

As you can see, not all energy storage products can be claimed under the credit, and the restrictions require the owner to track the charging source to accurately report their usage to the IRS.

Those restrictions would be lifted if the new bill proposed this month passes into law.

Proposed Changes Under the New Solar + Storage Tax Credit Bill

The latest bill introduced in the House seeks to remove the complicated limitations of the current incentives. Under the new bill, the full cost of all solar storage products would be eligible for the tax credit, just like all other system components.

There would be no partial credit or minimum charge restrictions. If you buy an energy storage system, it would be eligible for the full tax credit—period.

The change would make energy storage more appealing to the public, regardless of application, and add more momentum behind the adoption of storage-ready systems. That move is supported by solar enthusiasts and utility providers alike, as energy storage systems help smooth the demand curve, reduce the burden on the grid and prevent brownouts.

Interested in going solar with an energy storage solution? Take a look at our solar+storage packages and grab the free battery guide linked below for more info. If you have any questions, you can always call us at 1-800-472-1142 for a free consultation with a solar designer.

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How to File IRS Form 5695 To Claim Your Renewable Energy Credits

How to File IRS Form 5695 To Claim Your Renewable Energy Credits

Form 5695 Filing Instructions

This article provides quick step-by-step instructions to help you file IRS Form 5695 and claim your renewable energy credits. We’ve provided sample images of the tax forms to help you follow along.

The federal tax credit is a major incentive for going solar. If you build your solar system before Jan. 1, 2020, you’re eligible to claim 30% of your total project costs as a credit toward your federal taxes. The credit offsets any taxes you may owe, and rolls over for up to 5 years if the value of the credit exceeds your tax liability.

This article provides a simple step-by-step walkthrough that will explain how to file your taxes to claim the Federal Tax Credit for investing in renewable energy.

Before we start, you’ll need to gather your receipts for any project costs. You can claim the cost of the system as well as any associated installation costs (materials, hired labor, permitting fees, etc.).

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Free Federal Tax Credit Guide

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Step 1: Download Tax Forms

You’ll need four forms to file for the credit, which can be downloaded from the IRS website.

Form 5695

This is the Residential Energy Credits Form. We’ll be paying the most attention to this one.

Download 5695 here »

Form i5695

This is an information form about the 5695 that contains a worksheet we’ll be filling out.

Download i5695 here »

Form 1040

This is the Individual Income Tax Return form that most people use to file their taxes.

Download 1040 here »

Form 1040 – Schedule 3

This form covers tax credits, including the renewable energy credits. Add your Form 5695 results here to claim the credit.

Download 1040 – Schedule 3 here »

Step 2: Add Up Project Costs

First we need to know the total amount you paid to install your solar system. This includes the cost of components as well as any associated installation costs.

Gather your receipts and total any money you spent on the following:

  • Solar components (panels, racking, charge controller, inverter, wire, etc.)
  • Shipping costs
  • Solar consulting fees
  • Professional installer fees
  • Electrician fees
  • Engineer fees
  • Tools purchased or rented for PV installation
  • Equipment purchased or rented (scaffolding, man-lift, auger, etc.)
  • Wiring Screws, bolts, nails, etc.
  • Permitting fees
  • Other associated costs

Keep note of this total so that you can transfer it over to your tax forms.

Step 3: Start Form 1040

Begin by filling out Form 1040. This is your individual tax return. It’s a good idea to do this first since you will be referencing Line 11 (your total tax liability) later in this process.

Once you complete this form, switch over to Form 5695 to start calculating your residential energy credits.

Step 4: Start Form 5695

Form 5695 focuses on renewable energy credits.

Line 1: Enter the total amount you spent on your solar project, which you calculated in Step 2. We’re using $12,350 as an example, but be sure to enter your own total.

Lines 2-4: In this example, we’ll assume you didn’t invest in another form of renewable energy during the tax year. If you also invested in a solar water heater, wind power, or a geothermal heat pump, add those totals here.

Line 5: Total lines 1-4 and add them here.

Form 5695, lines 1 and 5

Line 6: Multiply the Line 5 total by 0.3. This calculates 30% of your project costs, the amount you can claim under the credit. Enter the result here.

Form 5695, line 6

Line 7: If solar was your only renewable energy purchase, check “No.” If you bought fuel cells, check “Yes.”

Lines 8-11: Skip these unless you purchased fuel cells during the tax year.

Line 12: If you claimed the solar tax credit last year and are rolling over a portion of that credit to this year’s taxes, enter the remaining value of the credit here. Otherwise, skip this step.

Line 13: Add the values from lines 6, 11 and 12. Enter the total here.

Form 5695, Line 13

Step 5: Fill Out Form i5695 Worksheet

Form i5695 contains instructions on how to fill out Form 5695. We need to complete the worksheet on page 3, then transfer that information over to Form 5695.

Line 1: Enter the total taxes you owe. This is located on Line 11 of your Form 1040. We’ve entered $21,442 as an example of what someone making $100k a year might owe. Again, enter your own results here.

Lines 2-9: Enter any other tax credits you will claim. For simplicity, we’ll assume there are no other credits.

Line 10: Add up lines 2-9 and enter the total here.

Line 11: Subtract Line 10 from Line 1. The result is the total value of the credits awarded to you. Enter it here.

Form i5695, Lines 1 and 11

Step 6: Complete Form 5695

If your credit is higher than your total tax liability, the remainder of the credit can be rolled over and applied to a future tax return.

Now that we’ve finished the worksheet, jump back to Form 5695.

Line 14: Enter the value from Line 11 of the i5695 worksheet you completed in the previous step.

Line 15: Check Lines 13 and 14 and enter the lower of the two numbers on Line 15. This ensures your credit doesn’t exceed your tax liability.

Line 16: If Line 15 is less than Line 13, subtract Line 15 from Line 13 and enter the value here. This is the amount of “leftover” credit that can be rolled over to a future return. This is not common.

Form 5695, Lines 13-15

We’re done calculating your renewable energy credits! Now we just need to add it to your individual tax return.

Step 7: Apply Form 5695 Results to Form 1040 – Schedule 3

Take the amount from Line 15 of Form 5695 and enter it on Line 53 of Form 1040 – Schedule 3.

Form 1040 Schedule 3

Attach Form 5695 and Schedule 3 to your Form 1040 when you file. (No need to include the Form i5695 worksheet.)

You’re done! Kick back and bask in your reward for investing in renewable energy.

If you have any questions about how the Federal Tax Credit works, or simply want to explore the possibility of going solar, give us a call at 1-800-472-1142. You can also grab our free Federal Tax Credit guide for more info.

Disclaimer: This guide is offered as basic instruction only and is not meant as professional tax preparation advice. For specific tax-related questions or issues, we recommend consulting a certified tax preparation specialist or CPA.

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Install of the Month – April 2019

Install of the Month – April 2019

Our April Install of the Month winners are Troy and Suzanne H. from West Virginia. They built their system in two phases, starting in 2014 and adding on in 2017 to build an array that produces 11.1 kW of solar power in total.

The project likely isn’t finished, either. They have their eye on retrofitting the system with a battery bank and converting to an off-grid setup as batteries become more affordable in the future.

As someone who grew up repairing his own cars and appliances, Troy was well-equipped to take on this solar build as a DIY project. Aside from an assist on the electrical hookup, Troy and his wife Suzanne were able to manage the entire build themselves.

Troy got back in touch with us to reflect on the process of going solar. Here’s what he had to say about the project:

What solar system type did you Install?


What was your primary reason for adding solar to your home?

Adding solar provided us the opportunity to not only produce our own power, reduce our carbon foot print and energy expenditures, but also to do our part to leave a better earth for our children and future generations. Eventually as battery technology becomes more affordable we would like to go off grid.

Did you have any previous DIY experience?

Growing up in rural West Virginia in a less than affluent family, I learned at learned at an early age from my father, in order to survive we had to be self sufficient. We had to maintain and fix our own vehicles, repair household appliances, perform general home renovation and maintenance, along with performing numerous other diy projects. In more recent years, my father and I, along with the help of family, converted a barn into a passive solar home.

What was the most difficult part of the installation?

I wouldn’t say anything in particular was all that difficult. However I got extremely lucky when my electrical inspector allowed me to use his crimpers to do an irreversible ground crimp. Prior to this, I called everywhere trying to rent or borrow one. To buy the crimpers that has the proper stamping die is very expensive. I performed the crimp while the inspector did his final inspection.

Probably my least favorite part of the install was jumping through hoops applying for permits from the power company.

How many helpers did you have?

My wife and I performed the majority of the install. We also got some help from other family members.

Did you hire a contractor?

The outstanding support from the technicians at Wholesale Solar made the entire process much easier. They made it possible to do the entire project without much outside help. Admittedly, before submitting my plans to the power company I had a Master Electrician friend review my plans and drawings.

Were there any unforeseen additional parts or tools you needed?

I can not imagine piecing out every nut and bolt, clamp or component on our pv system. Wholesale Solar did an awesome job putting the pieces together, making the install a snap.

How long was the full installation process?

We did our install in two phases. Phase one was a 6.9 kw ground array. The array sits 350′ from the house so it took a little additional work doing voltage drop calculations and running the lines. After the permitting process we rented a ten ton excavator to do the digging. We broke ground in September 2014 and that system went live in December of the same year. Phase two was a 4.2 kw roof array that included an EV charger. We started the install July 2017 and went live in September 2017.

How did it feel to get your solar project finished?

It was an incredible feeling of pride and accomplishment when we went online and started generating our own power. Our system not only provides 100% of our home’s energy needs (with the exception of a little wood for supplemental heating and a small amount of propane for cooking). It also provides energy for my wife’s EV to travel to and from work (home is the only place she charges), and we put excess (green) energy onto the grid that is used by our neighbors. Doing this in a coal state, where people said it couldn’t be done is beyond gratifying.

Who else did you consider before choosing Wholesale Solar?

We very quickly decided to go with Wholesale Solar as our PV supplier. Not only were their prices competitive with all out there, their tech support was second to none. After several initial calls to their tech support, I quickly realized they were the company for us.

What was your total solar install costs? (Ball Park)

Phase one’s total investment, including renting an excavator, additional direct bury electrical wiring, the ground structure, permits and inspections, before a 30% residential energy credit, totaled $17,688. Phase two total cost was $7204 before the 30% residential energy credit.

How much did you save on your taxes?

Though our state did not provide any tax incentives or rebates, we received a federal residental energy tax credit of $5306 on phase one and $2161 on phase two.

Components in Troy and Suzanne’s system:

Troy and Suzanne's Solar Breakdown:

  • System Cost: $24,892 including installation
  • Yearly System Output: 13,539 kWh per year
  • Federal Tax Incentive: Qualifies for $7,467 U.S. Federal Tax Credit
  • Utility Rates: 10.2 cents/kWh

It’s Your Turn

Thinking about making the switch to solar? Download our Getting Started Guide. We’ll walk you through everything you need to know about buying a solar energy system that covers your needs.

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Generator Sizing Guide For Off-Grid Solar Systems

Generator Sizing Guide For Off-Grid Solar Systems

Most off-grid solar systems are paired with a generator. Without utility power as a fallback, off-grid setups need a backup plan in case their solar system can’t produce enough to meet the property’s needs.

Gas generators are used in off-grid systems as a backup charging source to recharge the battery bank when solar can’t keep up with demand. They are also used for backup power in case equipment fails and the inverter system needs to be bypassed.

Here’s our advice on how to pick a generator for your off-grid solar system.

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Generator Sizing

As a general rule, the generator should be around 2 times the size of the inverter’s continuous output. For example, a 4,000-watt inverter should be paired with an 8,000-watt generator.

This is because the generator needs to charge batteries while still powering the loads (appliances using energy). If the loads total 4,000 watts, and the charger is 60 amps at 48 volts, that totals around 7kW of continuous power:

60a x 48v = 2,880 watts + 4,000 watts = 6,880 watts

8kW would make sense as a minimum generator size to power the loads and have enough power to charge the battery bank as well.

It’s a good idea to round up slightly to give some headroom for the generator, especially at higher elevations where your generator is going to lose some of its power. Engines can lose around 3% of their power for every 1,000’ increase in altitude. Make sure you account for this if your system will be installed at a high elevation.

Can I Use a Larger Generator?

A larger generator can be beneficial if you have large loads like an air conditioner or a welder that will only be used when the generator is running.

We frequently sell 12kW and 14kW Kohler generators with our off-grid systems using a 4000w inverter. A larger generator is going to burn more fuel, but otherwise will work fine.

Can I Use a Smaller Generator?

Smaller generators will still work, but it typically requires adjusting the settings to limit the battery charger’s output. Most battery chargers allow you to adjust the AC input amperage and charge rate.

You will need to match the generator’s voltage with the inverter. For example, 120Vac generators should be paired with 120Vac inverter/chargers, while 120/240Vac generators need an inverter that outputs 120/240Vac.

In the rare case that you are using a three-phase generator or inverter, the same rules apply: the generator’s voltage would need to match the inverter.

There is one exception we are aware of. Magnum PAE inverters are 120/240Vac but can handle a 120Vac input, provided you turn down the charge rate to 50% or lower, and adjust the AC input amps to match the size of the generator. This is useful if you need an inverter that can output 120/240Vac but are working with a smaller generator.

Generator Fuel Type (Natural Gas, Propane, Diesel)

Most standby home generators work on natural gas, propane or diesel. Diesel generators tend to be much more fuel efficient and longer lasting, but the initial cost can be 2-3 times more than a natural gas or propane alternative.

The Kohler 12kW & 14kW generators we sell can work with either natural gas or propane. Off-grid customers typically use propane instead of natural gas, but these models can be configured to work with either fuel type.

Other Considerations


Most generators don’t have a warranty that covers off-grid or prime power applications. Check the generator warranty closely to be sure it can be used off the grid.

Kohler’s 12RES and 14RESA generators are both warrantied for 18 months / 1000 hours of off-grid use (whichever comes first).

If you need more power, dual 14RESA generators can be combined in parallel with the Kohler Powersync module for 28 kW of output.

2-wire start

Off-grid generators paired with solar power systems need 2-wire start capability to allow the automatic generator start (AGS) function to work. When your batteries drop below a certain voltage, the AGS kicks in to turn on the generator and recharge your battery bank.

Note that 2-wire start is different than electric start. Some generators will have a button for electric start/stop, but they can’t be controlled by a 2-wire signal, which means the inverter can’t communicate with the generator to trigger the AGS mechanism.

The Kohler 12RES and 14RESA are both capable of two-wire start.

1800 RPM vs. 3600 RPM

Most generators operate at one of two engine speeds: 1800 or 3600 RPM.

The difference is based on engine design and the alternator being used. 1800 RPM generators are generally considered superior because they are more fuel-efficient, but they cost quite a bit more up front. 3600 RPM generators tend to be cheaper but less efficient.

The Kohler 12kW and 14kW generators we sell are 3600 RPM. They are very durable, reliable and more cost-effective for typical off-grid applications. Kohler doesn’t make any 1800 RPM generators smaller than 24kW, although there may be options from other manufacturers. Be sure to do your research and read reviews to learn about the company and make sure you are getting a quality product.


When searching for a generator to support your off-grid solar system, keep a few things in mind:

  • Generator output should be 2x your inverter’s output
  • Match generator voltage to inverter voltage
  • Generator must be warrantied for off-grid use
  • 2-wire start is mandatory to work automatically with solar system
  • 3600 RPM generators are more cost-effective, while 1800 RPM generators cost more up front but last longer and are more efficient

For more help moving off the grid, check out our Solar Battery Guide, which explains how to size and select a battery bank to adequately support your energy needs off the grid.

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SMA Sunny Boy Review: Pricing, Specs, Pros and Cons (2019 Edition)

SMA Sunny Boy Review: Pricing, Specs, Pros and Cons (2019 Edition)

SMA Sunny Boy Review: Quick Summary

The SMA Sunny Boy costs less than other grid-tie inverters, but it only works if you build your system in full sunlight and face all your panels in the same direction.

The Sunny Boy is our preferred choice if you don’t need panel-level power optimization. But if you face issues with panel layout or shading, you’ll be better served by the SolarEdge HD-Wave or Enphase micro-inverters.

SMA has long been regarded as one of the most reliable string inverter manufacturers in the solar industry. In this article, we’ll review the SMA Sunny Boy, our pick for best inverter for “standard” grid-tied solar systems.

The Sunny Boy shines in systems that won’t be affected by shading, panel orientation, or other concerns that would impact production from your panels.

It’s not the most versatile, high-tech inverter around. But if you’re building a typical fixed-mount system that will receive full sunlight year-round, the Sunny Boy gives you more bang for your buck than any other grid-tied inverter on the market.

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SMA Sunny Boy Pricing

SMA offers a range of Sunny Boy models from 3 kW to 7.7 kW for residential grid-tie systems. Please note that the prices published here are current as of 3/11/19, but are subject to change in the future. Click the product links to view current pricing in our shop.

ModelPriceCost Per Watt
Sunny Boy 3.0kW$1,22541 cents/watt
Sunny Boy 3.8kW$1,25032 cents/watt
Sunny Boy 5.0kW$1,32526 cents/watt
Sunny Boy 6.0kW$1,42524 cents/watt
Sunny Boy 7.0kW$1,67524 cents/watt
Sunny Boy 7.7kW$1,72522 cents/watt

SMA Sunny Boy 7.7 kW Specs

Here’s a quick look at the specs for our most popular Sunny Boy model, the 7.7 kW configuration. It’s worth noting that the 3.0 and 3.8 kW models have 2 string inputs (instead of 3), but other specs like efficiency, warranty and voltages are the same for all the residential models listed in the table above.

  • Model: Sunny Boy 7.7 kW
  • Wattage: 7700 watts
  • Peak Efficiency: 97.5%
  • Warranty: 10 years
  • Input voltage: 600V DC
  • Output voltage: 240V AC
  • String Inputs: 3

Ideal Application For The SMA Sunny Boy

It’s important to understand the limitations of string inverters to help decide whether they are the right choice for your project.

A panel string is a group of panels that is wired into a single input on the inverter. Because the panels are wired in series, the production of every panel in the string is linked together.

If one panel suffers a drop in production, every panel in the string drops to match the output of the weakest panel.

Panel string diagram
Panel strings are wired in series. Production drop from one panel translates across the entire string.

You may own a string of 330W panels, but if a single panel in the string falls to 250W production, every panel in that string is going to produce 250W of power. That’s an 800W production loss over a 10-panel string—nearly a 25% loss in output.

For this reason, the Sunny Boy only makes sense when you can build your panels in a location that is fully exposed to sunlight year-round.

If trees, chimneys or other obstructions throw shade on a panel, it will cripple the production of a string, which affects your entire system.

It’s also not ideal if your panels face different directions—if you need to spread them across an unusually-shaped roof, for example. Panels work best when they face directly into the sun (ideally, you want to point them toward the Equator, which means a South-facing array is ideal for systems built in the US).

If some panels in a string face South and some panels face East, the East-facing panels will produce less power because they don’t point directly into the sun. The entire string will drop to match the output of the East-facing panels, sacrificing the extra output from those that face South.

Different strings can have different orientations, but all panels in a string should face the same direction.

To mitigate these issues, you would be better served by an inverter system with panel-level optimization like the SolarEdge HD-Wave or Enphase IQ7+ micro-inverters.

However, if you don’t need to worry about shade or panel orientation, Sunny Boy systems are extremely reliable and efficient at a price that is 15-25% less than alternative options. It’s the best value you can find on an inverter, assuming you meet these ideal build requirements.

Compare your options with our video review of the best grid-tie inverters on the market:

Pros of the SMA Sunny Boy

Best Value Inverter on the Market (In Ideal Conditions)

The Sunny Boy is the most cost-effective grid-tied inverter you can buy, provided your system meets a few criteria:

  • Built in full sunlight (not blocked by trees, chimneys or other obstructions)
  • Panels face the same direction
  • Large enough to meet minimum string sizing requirements (at least 4-6 panels depending on the panel and inverter models you choose)

Let’s compare two systems that would produce 906 kWh per month, enough to offset the national average energy usage for American households. (Prices are current as of 3/7/19.)

The systems are identical aside from the inverter equipment, and the Sunny Boy system costs nearly $1,600 less than the HD-Wave. You can save quite a bit of money if your system is built in full sunlight and you don’t need the power optimizers featured in the HD-Wave system.

Secure Power Supply

A feature unique to SMA inverters is the Secure Power Supply (SPS). The SPS provides a source of backup power in case of emergencies.

If your power goes out, you can plug into the SPS, a 2000-watt power source that draws backup power from your panels even if the grid is down. This is a nice failsafe to power critical appliances during an outage.

One caveat is that your panels must be exposed to sunlight and producing power for this to work, since the SPS draws electricity in real-time from the panels to make this feature work. At night or during heavy storms, the SPS is not a reliable substitute for a fully-equipped grid-tie system with energy storage.

Optimizers Are Optional

The SolarEdge HD-Wave comes with mandatory power optimizers—the system won’t work without them. With the Sunny Boy, the optimizers are an optional add-on.

This gives you the flexibility to start with the base Sunny Boy package, then retrofit optimizers on to the panels if you think they’re necessary.

For example, your system might be fully exposed to sunlight in the summer, but then you find that your house casts a longer shadow in the winter and covers part of your array. You can go back and add optimizers to the shaded panels to bring their production back up to par.

There is a trade-off, though. When you add optimizers, the Sunny Boy loses its Secure Power Supply functionality. This is a design oversight that we hope to see corrected in future models.

Nevertheless, it’s nice to have the flexibility to retrofit your panels with power optimizers should the need arise.

Great Customer Support

SMA has some of the best customer support in the industry. Their customer-facing tech team is knowledgeable and has great response time via phone and email. They also produce detailed product documentation to help people install, program and troubleshoot their equipment.

As a distributor, we’ve found them to be fair and responsive working with us to troubleshoot faulty equipment and process return claims.

In an ideal world, great support should come standard, but unfortunately that’s not always the case. Some solar manufacturers don’t even offer direct-to-consumer support, instead forcing the distributor to mediate technical issues and return claims.

Not SMA, though: their support team is one of the most accessible and competent in the business.

Cons of the SMA Sunny Boy

System Design Limitations

As mentioned above, the Sunny Boy works best if all your panel strings face the same direction and you can build your array in full sunlight.

If you don’t meet these requirements, production will drop fairly dramatically, and the Sunny Boy is no longer the most cost-effective option.

While the Sunny Boy shines in its wheelhouse, it’s not the most versatile inverter on the market. The SolarEdge HD-Wave is more fully-featured and tends to be the better pick when you need panel-level power optimization.

Rapid Shutdown Limitations

The newest electrical codes (NEC 2017) require rapid shutdown for PV systems installed on buildings.

For Sunny Boy systems, that requires adding optimizers, which means you lose the SPS feature—and the cost advantage over other inverters. A Sunny Boy with optimizers costs about the same as a SolarEdge HD-Wave system.

If you know you need optimizer technology from the start, you’re better off with a SolarEdge or Enphase system, which are built from the ground up for that purpose. SMA’s optimizers are an add-on to the Sunny Boy, which wasn’t originally designed with power optimization in mind.

Rapid shutdown requirements only apply in certain areas, and only when the system is installed on a building. Roof-mount systems often require optimizers to comply, but in many cases ground-mount systems are exempt.

Harder to Install

The Sunny Boy is larger and heavier than other inverters, making them a bit more challenging to install, especially for a DIYer working alone.

Larger Sunny Boy models weigh 57 pounds. They can be pretty hard to manage when you’re trying to lift and mount the inverter on your wall.

(Believe it or not, older models were heavier because they ran on transformers, while the latest Sunny Boy line is transformerless. Still, the Sunny Boy 7700 weighs more than twice as much as the 26.2-pound HD-Wave 7600).

It’s the largest and heaviest inverter we stock, and can be a bit challenging to mount if you are installing your own system without any outside help.

Short Warranty

The standard 10-year warranty is shorter than SolarEdge’s 12-year warranty on the HD-Wave, and much shorter than the 25-year warranty on Enphase IQ7+ micro-inverters.

You should expect to replace your Sunny Boy at least once, and possibly twice, over the life of your system.

SMA does offer an extended warranty plan that allows you to stretch the product warranty up to 20 years. Whether you buy the extended warranty up front or replace the inverter out of pocket later, you’ll incur some additional costs for a replacement at some point. Those costs should be factored into the lifetime ownership cost for your system.

SMA Sunny Boy: The Verdict

Our evaluation of the Sunny Boy is pretty simple. If you can build in full sunlight and don’t have any complicated layout requirements, the Sunny Boy is the best all-around value you can find.

If you need more advanced power optimization for individual panels, are working with an unusual array layout, or simply want a system that is easier to install, the SolarEdge HD-Wave or Enphase IQ7+ micro-inverters are going to be better options.

Download your free solar inverter guide