Category: Solar Products

How Many Solar Panels Do I Need?

How Many Solar Panels Do I Need?

IAN SHURTLEFF, Sales and Design Tech at Wholesale Solar​

One of the most common questions our design technicians get is: “How many solar panels do I need?”

The answer is pretty complex, and frankly, most people approach it from the wrong angle when they start to look into solar.

We’re often asked to quote a system to power a 3-bedroom home or a support a family of 4. In these situations, it’s impossible to provide an accurate estimate until we know more about the household’s energy needs.

In reality, the best place to start is to evaluate your current energy use based on past electric bills. Past usage data is the best baseline to figure out how many panels you will need.

Lifestyle, climate and panel efficiency all play a role in figuring out the size of your solar system. Here’s the process we use to make an accurate estimate.

How many panels for grid-tied systems?

In order to figure out just how many panels you need, you’ll want to gather up 6 months to a year’s worth of electric bills. If you live in an area with snowy winters or blistering hot summers, look at a larger sample of bills to understand when your usage spikes. Take peak periods into account as you estimate how many panels you’ll need to cover your energy usage.

Some companies provide a 12-month summary of how much electricity you use on every bill. Depending on your utilities provider, you may just need one bill to find an estimate for the year.

Got your paperwork in order? Great – you want to look for how many kilowatt hours (kWh) of electricity you use per year.

Wait, what’s a kilowatt hour?

A kilowatt hour (kWh) is a measurement of energy. If an appliance rated for 1 kilowatt (1000W) runs for an hour, then one kWh of energy has been used.

The energy company measures total energy usage in kilowatt hours. Your total usage in kilowatt hours determines how much you are billed each month.

Example 1: A fridge rated at 250 watts runs for 4 hours per day. 250W x 4 = 1000W, or 1 kW. This fridge uses 1 kWh of energy over the course of a day.

Example 2: An oven is rated at 2000 watts (2 kW). Cooking in this oven for half an hour would consume 1 kWh of power (2kw x 0.5 hours = 1kWh).

Find how many kWh of energy you use per year. That will give you a good jumping off point for estimating your energy needs – but you’re not there yet.

Divide that number by 365 to get your daily energy usage in kWh.

Once you have your daily energy usage, use this formula to estimate your total system size:

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

Sun-hours refers to how much sun you get each day where you live. You can find that info on our US sun-hours map. More on this a bit later.

The inefficiency factor simply accounts for circumstances that would make your system run below its optimal output, like shade, extreme temperatures, voltage drop and equipment inefficiencies.

Take your daily usage and divide it by these two numbers to get an estimate of the overall output of your system.

For example:

According to the U.S. Energy Information Administration, the average American household used 10,766 kWh of electricity annually in 2016. That’s about 29.5 kWh per day.

Let’s say you live in Arizona, which gets 5.5 sun-hours per day.

29.5 kWh per day ÷ 5.5 sun-hours ÷ 0.9 = 5.9595 kW capacity system.

That would give you an approximate system size of 5.96 kW, or 5959W (remember, 1 kilowatt = 1000 watts).

From there, the last step is to divide by the energy rating of each individual panel. Solar panels are graded by how much power they use. The panels you would use in a residential setting typically range from 275 to 350 watts per panel.

Let’s say we want to use Astronergy 325W panels. Take your system size and divide by the panel wattage to figure out how many solar panels you need in your system:

5959W ÷ 325W = 18.33 panels

Round up the final number, since you can’t buy partial panels. In this scenario, we would need 19 panels rated at 325 watts apiece to cover our energy needs.

We can’t stress this enough: this calculation is a very rough estimate. It should only be used to ballpark system size and make early pricing estimates.

But don’t take this estimate as gospel – there are too many factors that can change the size of your system in practice.

Additional considerations for off-grid systems

Calculating power consumption needs for an off-grid system is a tad more complicated. People who live off-grid need to focus on daily power usage rather than monthly or annual consumption.

You’re not staring down a power bill each month – you’re independent and responsible for covering your own day-to-day power needs. The system needs to be able to produce enough (and store enough) to keep things running smoothly.

Without power bills as a starting point, it’s best to start by listing out your major appliances and estimating how much you use them on a daily basis. Input this list into our Load Evaluation Calculator.

If you’re not sure how much power an appliance uses, follow the appliance electrical consumption table as a guide. You can also check for the EnergyGuide sticker, or use a meter to measure energy consumption if possible.

This form will give an estimated daily usage.

Pay close attention to December and January when you estimate your energy needs. Those months tend to have the highest power usage and the lowest output by your system.

When you live off-grid, you will need a battery system that’s large enough to store enough power for the day and then use solar power to recharge them in a timely manner. It’s common to lean on a backup generator during the winter, when there won’t be enough sunlight to fully power your solar system.

Once you know how much power you use in kWh per day, a solar design technician can determine the minimum battery size needed with a formula that accounts for things like inefficiencies and temperature coefficients.

Here are the basic formulas we use to size off-grid systems:

Minimum Battery capacity (for lead acid batteries):

Daily usage (kWh) x 2 for a 50% discharge depth x 1.2 inefficiency factor = Minimum Battery Capacity

Minimum Solar Array Size

Daily usage (kWh) ÷ Sun-hours ÷ .9 inefficiency factor = Minimum Solar Array Output*

*Ensure solar array meets battery charge requirements, typically around 10 charging amps per 100ah battery capacity.

You may need a larger array or battery bank based on your location, ambient temperature, your usage patterns and other factors. Take a look at our Battery Bank Sizing Calculator to help figure out how many batteries you need to power your system.

Factoring in sun-hours based on your location

“Sun-hours” refers to how much solar energy hits a given area over a certain amount of time.

Your local climate determines how many peak sun-hours you get each day. This number can change drastically based on where you live. If you live in the United States, you can check out our Solar Insolation Map to get an estimate of how many sun-hours you receive in your area.

It’s important to keep in mind that the term “sun-hours” doesn’t just refer to the hours of daylight that your area receives. The peak hours occur when the sun is at its highest in the sky, which will change based on the season and how close you are to the equator. In the winter, the average sun-hours in your location could decrease by 25% to 50%.

So how do sun-hours affect the number of panels on your solar system? If you live in an area with less sun-hours, you’ll need more panels to capture what you need to cover 100% of your energy usage. However, if you live in an area that gets 5-6 sun-hours per day, you might be able to get by with a smaller system.

Quality vs. quantity: panel efficiency isn’t everything

Another aspect that affects the size of your system is the efficiency of the solar panels themselves. Most residential panels range from 275W to 350W. If you go with a 275 watt option, you’ll need several more panels to build your array.

When it comes to solar, efficiency isn’t always the most important factor to consider when you build your system. It really depends on what your specific goals are.

For example, if you look at your solar panels primarily as an investment and a quick ROI is your biggest goal, you might be better off with a lower output, lower cost panel.

“If a panel is 50% more efficient, but costs 100% more, you’re better off paying for [a larger system] of less efficient panels.”

-Brady Schimpf, technical marketing engineer at Ironridge

Brady Schimpf, technical marketing engineer at Ironridge, he had a few thoughts on this matter. He said one of the most common mistakes he sees people make is that they buy into ultra-efficient, high-quality, and technically advanced system, and it might not be worth it – especially if ROI is your biggest concern.

“While a lot of the proprietary systems like that have really good equipment, it is important to look at the cost per watt,” he explained. He urges consumers to consider this: “How much are you paying for the total wattage/production of the system?

“It doesn’t really matter how efficient a panel is if it costs a lot more. If a panel is 50% more efficient, but costs 100% more, you’re better off paying for [a larger system] of less efficient panels.”

But there are some circumstances where having a smaller yet more efficient solar system makes sense. For example, if your roof space is really limited, you might need a more efficient system to cover your energy needs within that given area.

Considering other variables when designing a solar system

We can’t stress this enough: this breakdown only serves as a very rough estimate and a starting point for planning your system.

It’s great to get you closer to a ballpark figure on the cost of panels. It will help as a benchmark when you measure your roof to see if you can fit a system up there.

But when you get deeper into planning your system, unexpected hurdles always come up and the system size tends to change.

What if you decide to go with 275W panels instead of 350W panels because the cost-per-watt is lower? What if shade covers your system, or your roof doesn’t directly face the sun? What if harsh weather causes your equipment to perform below its rated efficiency? What if you start using more energy than you did in the past?

Yup . . . you’ll need more panels.

Although this breakdown can give you an estimate of how many solar panels you’ll need in your array, at the end of the day it’s just an estimate. There are several other variables that can determine the size of your solar system, but this process is still important as it gives you an idea of what to look for before you seek out quotes on solar systems.

If you’re interested in going solar, the best thing you can do is speak with a solar design technician that can help you find the ideal system for your unique situation. Bring your estimate as a starting point. We’ll go over any potential problems and tweak the design to suit your location and lifestyle.

Ground Mount vs. Roof Mount Racking: What’s the Best Way to Mount My Solar Panels?

Ground Mount vs. Roof Mount Racking: What’s the Best Way to Mount My Solar Panels?

COURTNEY JOHNSTON, Purchasing Manager at Wholesale Solar​

Once you have your solar panels picked out, it’s time to decide which mounting system is best for your living space, budget, and energy needs.

There are two types of solar mounting options: roof mount and ground mount racking systems. Roof mount systems affix to brackets on your roof, while ground mount systems are built into a foundation at ground level. See the comparison images below for examples.

Ground Mount

Roof Mount

There are benefits and drawbacks to each, and both mounting systems have their merits depending on your project specs. This article will dive deeper into what we think about when we recommend ground mount vs. roof mount racking to our customers.

But first, a quick summary:

Ground Mount Solar Racking


  • Easy to access
  • Easy to clean
  • Easier to troubleshoot
  • Stronger racking overall
  • System is not confined to the dimensions of the roof
  • Cooler panel temperatures means higher energy output
  • No need to remove panels if roof is replaced


  • Installation is more labor intensive
  • Installation is more expensive
  • Requires more parts and pieces
  • Permitting process is more expensive
  • Takes up real estate
  • Not aesthetically pleasing to everyone

Roof Mount Solar Racking


  • Less expensive
  • Requires fewer materials to install
  • Installation labor cost is lower
  • Utilizes unused space
  • Easier to permit


  • Hard to access – especially if your roof is steep or slippery 
  • Harder to troubleshoot errors
  • Higher panel temperatures mean lower panel output
  • Space constraints on the roof limits the size of the system
  • Can be a hassle if you need to replace the roof within the panel’s lifetime (might install the system twice)
  • Putting holes in your roof could lead to water damage

Why Go Ground Mount?

The Perfect Alignment

No matter what kind of solar system you’re considering, this much is true: every solar array works best when it’s able to get as much sunlight as possible.

If you live in the United States, you’re north of the equator, so the sun leans south as the Earth orbits. Facing your array true south will capture the most daylight and produce the best results. However, if you live south of the equator in South America, it would be more efficient to face your system true north.

Getting the perfect alignment can be a little tricky for a roof-mounted system. It isn’t likely that your roof naturally faces directly into the sun.

Ground-mount systems can face any direction you want. You can align your system at the optimal angle so it points directly at the sun. For that reason alone, ground-mounted systems are most efficient, as they maximize access to the sunlight that powers the array.

Benefits for Off-Grid & Grid-Tied Consumers

The perfect angle isn’t the only thing that makes ground-mount arrays more efficient. Being raised off the ground allows for better airflow and cooling, which means your panels produce more energy.

Most solar panels are tested at an average of 77° Fahrenheit – a normal sunny day, but nothing too extreme. But when it gets hotter than this, and the panels grow less efficient, producing 10-25% less electricity. The semiconductors suffer greater resistance to the flow of electricity. Think of it like squeezing the hose when there’s water running through it.

Proper airflow and cooling keep your panels running in optimal conditions, which is a clear advantage for ground-mount racking.

Giving You Room to Grow

If you’re installing on your roof, chances are you’ve got limited space to make the most efficient array possible. Should your energy needs change in the future, it could be challenging to add more panels to your current system.

When you go ground-mount, you’re under no such restriction – assuming you have the space in your yard. You can expand your array after the initial installation, and many ground mount racking options allow you to bolt on new additions easily.  

This means if you add on to your property and require more power, or if you find that your initial power supply just isn’t cutting it, you can add more panels as needed with minimum fuss.


Another major benefit to ground mounted solar is accessibility. Solar systems require a lot of trial and error, especially in the installation phase. It’s a pain to have to get up on the roof every time you need to work out a kink with your system.

This is an even bigger selling point if you’re considering a system with microinverters and optimizers. With those accessories, there is a component under each solar panel and they can be difficult to replace on a roof-mounted system.

What happens if a microinverter in the middle of the array breaks down? In that case, you would have to remove several panels to access the source of the problem. When your system is on ground level instead of high up on the roof, it’s easier to troubleshoot panels and accessories.

Ground mount also makes it easier to clean your panels and perform routine maintenance on them. It provides you with more peace of mind to know you won’t have to risk your safety every time you need to brush snow off the panels, wash off dust and pollen, or remove debris from under the panels. There are also pole mounts available, which are ideal for heavy snow areas. Pole mounts can be constructed with adjustable tilt angles to maximize energy production and easily shed snow in the winter months.

Drawbacks Of Ground-Mounted Solar

Now for the drawbacks of ground-mount racking that you might want to consider.

In general, a ground mount is a lot more complicated to install and requires more money upfront to get the job done. If your primary concern is seeing the maximum return on your investment into solar panels, roof mount could be the way to go. The permitting process will be lengthier for a ground-mount system. And it will take up more space on your property, which you may prefer to use for something else.

More Labor Intensive & Requires More Cost Upfront

The main reason why a ground mount requires more cost upfront is because the system requires more parts to be assembled.

Think of it this way – when you place a solar array on the roof, half of the structure has already been built for you. But when you place a solar array on the ground, you have to build a sturdy roof-like structure to hold the panels in place.

This process involves getting your soil surveyed to make sure it can hold the system firmly in place, digging large holes, and paying extra for parts to build a suitable foundation for the panels.

Roof-mounted systems skip a lot of these costs. Assuming your roof is in good shape and doesn’t have structural damage, it should be strong enough to support the weight of the solar array. You don’t run into any of the hassle of building a brand new foundation to hold the panels in place.

Ground-Mount Racking Requires a Longer Permitting Process

Additionally, the city or county you live in might have a heavier hand in the installation process, since the system is considered a new structure. Depending on where you live, you will have to go to the authority having jurisdiction (AHJ) and obtain a building permit.

This will add extra challenges to the process. You’ll need to:

  • Submit a design plan
  • Consider soil type and property line setback requirements
  • Pay permitting fees

Ground-Mount Takes Up Real Estate

The final drawback to ground mounted solar is that it takes up a lot of space on your property. When you mount a system on your roof, it will be more discrete, and you get to keep the space on your land to do whatever you please.

The space issue isn’t a big deal if you have a large property. People who live out in the country tend to be able to find space for a ground-mounted system that won’t interfere with how they live the rest of their lives.

But if you own a smaller property, your roof may be the only place your solar array will fit. In some cases, a ground-mounted system isn’t even an option.

If space isn’t an issue, the decision often comes down to aesthetics. For those that consider ground mounted solar an unsightly blemish on their land, there are some artistic or unique installation options out there, such as those featured below.

But for the most part, people are proud of their solar arrays because they are a cutting-edge technology that represents freedom from the power company and total independence.

We like it when people show off their systems with a sense of pride. But there’s nothing wrong with preferring one look over another. For buyers who have the luxury of space, the decision often comes down to whether they think ground or roof-mounted systems look better.

Key Points To Consider:

Go with a ground-mount system if you want to simplify the maintenance / cleaning process and maximize energy output over time. There are three main questions to ask yourself to make sure ground-mount will work for you:

How much are you looking to spend upfront?

A ground-mount racking system requires more labor and parts to install it. You may need to partner with a contractor to get the job done, and the permitting process will be lengthier and more expensive.

But consider this: once the panels are installed, the upfront cost will be offset down the line by a more efficient energy output. There’s also less cost and hassle involved if you have to remove the panels for re-roofing.

You’ll shell out a bit more cash at the start, but the effort will pay for itself over time.

What kind of soil do you have?

If your property is on bedrock or if you know the soil is going to be really difficult to dig into, you might want to put the panels on your roof. Hard soil can make installation costs for ground-mount systems skyrocket. It’s not impossible, but you’ll need to rent heavy-duty equipment to drill into the ground.

There are also a few workarounds with ground-mount options to keep the digging to a minimum. A ballasted system might be a good solution. Learn more about the different racking options available in our article covering frequently asked questions about ground-mount racking systems.

Will you need to expand your system?

If you don’t plan on living off-grid, a rooftop system will probably be more than enough for your energy needs. However, if you are planning to go off-grid, the ground mount will allow you to add more panels as your energy needs change over time and you will get the benefit of a built-in tilt that can face towards the sun more easily than your roof.

When is Roof-Mount Racking Better?

Neither mounting system is “better” than the other – the choice depends on how your budget, energy needs, and lifestyle come together. A roof-mounted solar system tends to be a better option for customers who:

  • want to maximize their ROI
  • want a system that is simpler to install
  • don’t have a lot of space
  • want to spend less money upfront

Less Materials & Labor Means Less Cost Upfront

One thing that makes a roof-mounted solar system an easy sell is that it requires less time and money upfront to install.

When you put a solar system on your roof, the most complicated part of the structure is already in place. You don’t have to dig holes, get the soil surveyed, worry about your property line, or purchase expensive materials like poles and concrete.

The set-up is ideal for grid-tie customers that want to make a smart investment; installing on the roof instead of the ground can save you thousands of dollars.

Makes Use Of Unused Space

More often than not, a roof mount is used in a residential setting where there isn’t a lot of space for a ground-mount system. You might live in a condo or tightly-packed suburb. What scarce yard space you have might be better used for barbecues or a place for the kids to play. Mounting panels on the roof allows you to use space that would otherwise be useless, saving the rest of your property for the things that matter most.

Even for people with lots of land, some choose to install solar panels on the roof because it’s more inconspicuous. It keeps the space on your property free for things like raising animals, farming, and outbuildings. Roof-mounted systems keep the clutter off your land, so there’s more room to get things done.

Added Insulation & Protection

One unexpected benefit to a roof-mounted system worth mentioning is that it protects the roof from degrading elements like UV light, wind, rain, and snow. It will also keep your structure more insulated. If you’re living off-grid, this can be a nice way to keep the house naturally warmer at night and cooler in the daytime.

According to this article from Earth Sky, students at UC San Diego found that solar panels kept the roof an average of 5° Fahrenheit cooler than an exposed rooftop, which saved the building an average of 5% on cooling costs. Those savings are on top of what you’ll save on your energy bill anyway by going solar.

Easier To Permit

Are you one of those people who doesn’t like to get tangled up in bureaucratic procedures? A roof-mounted racking system is perfect for you. It involves a much simpler permitting process. You can submit the blueprints for your home to show whether or not your roof is structurally sound, and you’ll have to make sure your wiring and electrical systems are up to code. This typically won’t be an issue unless you live in an old home.

There’s no extra design paperwork to submit, because you aren’t building a new structure on your property – something that would lead to a much longer approval process.

Drawbacks Of Roof-Mounted Solar

What makes people shy away from roof-mounted systems? There are a couple downsides to consider:

  • Inaccessible due to their height
  • Less efficient, depending on the positioning of your home
  • Harder to modify and troubleshoot
  • Space constraints on smaller rooftops

Accessibility Makes Things Harder To Troubleshoot

For anyone that’s ever installed Christmas lights or cleaned out the gutters on their home, you know what a pain it is to get up on the roof. Depending on your mobility and planned level of involvement in the installation process, you may want to consider the accessibility of your roof. Depending on the pitch and what kind of material your roof is made out of, you may not want to risk getting up there. For example, metal roofing is really slippery.

Less Efficient

Roof-mounted systems are rarely as efficient as ground-mount systems. Rooftop solar panels can’t always be aimed directly at the sun. It’s a lot harder to angle an array on an existing structure so that it is optimized for full power consumption during peak hours.

You’re at the mercy of the built-in specs of your roof, which means you can’t always get the panels facing true south (above the equator) or north (below the equator). To compensate, you may have to buy a few extra panels to match the output of a perfectly aligned ground-mount system.

Space Constraints

The average roof area on a standard, medium-pitch roof in America is 1,500 square feet. Some of this space will be unusable due to chimneys, vents, and other obstructions. There’s not a lot of space left to work with.

Once your system is in place, it will likely be impossible to add on to that system if you need to increase your energy production. If your family grows or you add an extension to your home, it could be challenging to add extra panels to adapt to increased energy consumption.

Key Points To Consider

If you think rooftop solar is the best option for you, be sure to consider some commonly overlooked questions:

How old is your roof?

A roof and a solar system have a similar lifespan, so it makes sense to install them at the same time. Roofs less than 5 years old will likely be fit for solar panels. Any older than that and you at least want to consider whether it’s a good idea to replace it at the same time you install the panels.

If your roof is really old, there may be damage, leaks or structural integrity issues to worry about. It will need to be in good shape to support the weight of the solar array. Try to anticipate roof repairs before installing your system. It’ll be a huge pain in the butt to repair your roof after the panels are installed.

Does your HOA have constraints on where you can mount your panels?

Depending on the solar access laws in your state, a homeowners association (HOA) can prevent you from installing solar panels. Before you purchase your solar system, check in with your HOA to see if they have any guidelines regarding solar. You can negotiate any problems with them while you get the permitting in order.

How expensive is your electricity?

Even though solar panels are an excellent investment, it requires a big financial commitment upfront and it can take time to get a return on that investment depending on your energy consumption. If your energy consumption is small, your savings will be too. A lot of those savings can depend on your state and whether or not you live in a remote area that has expensive electricity. So even though we are big supporters of solar, it’s not for everyone – it really depends on your core goals.

To discover your key goals and find the perfect solar system for your specific needs, download our Getting Started With Solar Guide.

What’s the Best Off-Grid Solar Inverter?

What’s the Best Off-Grid Solar Inverter?

By JOSH ROELOFS, Products Manager at Wholesale Solar

If you’ve spent any time researching solar energy, by now you’ve heard of an inverter.

The inverter is like your solar system’s brain. It manages your power flow, controlling two kinds of power.

DC—or direct current—power is the kind stored in batteries. It’s also the kind produced by solar panels.

But you can’t use DC power (directly) to power anything in your home. That’s where your inverter comes in.

Everything in your home uses AC—or alternating current—power. And an inverter takes DC power from your panels (or from batteries) and turns it into AC so it can be used for your fridge, lights, TV, and other household appliances.

Simple, right?

How IS an off-grid inverter different from a grid-tied inverter?

A grid-tied inverter takes DC power from solar panels, turns it into AC, and sends it into the grid for credit.

Grid-tied inverters are simpler and easier to wire since there are usually only two main components—the inverter itself and your solar panels. (Some grid-tied systems are starting to incorporate energy storage, but most don’t have any batteries at all.)

But an off-grid inverter needs a battery bank to function.

Here’s how it works: your solar panels feed DC power into the batteries. Then your inverter takes that power and “inverts” it, creating AC power for your home. This works essentially like a miniature power grid.

(In case you’re curious, no, your inverter won’t deplete your batteries provided your system is set up and designed right. The battery bank gets recharged by your solar panels and a charge controller, and by a backup generator in the winter months.)

As you might imagine, off-grid systems are more complicated, thanks to additional components like the charge controller, battery monitor, and additional AC and DC circuit breakers. All of these things tend to make off-grid systems more difficult to wire and install.

It can also be a challenge to buy off-grid equipment because there are a lot of associated accessories: remote controls, battery monitor, breakers and enclosures, surge suppressors, and so on.

Picking the right parts can be confusing enough—but there’s no more critical decision than buying the right inverter.

How to choose an off-grid inverter

Think About Size

The first thing to think about is how much power you need.

Fortunately, sizing off-grid inverters is straightforward if you know what appliances you’re going to use.

Add up the wattage of all your lights and appliances to calculate the number of watts you’d need if everything was used all at once. (No, you’re not likely going to use everything, but this is an easy way to be safe.)

Don’t forget to consider the voltage—although most appliances run on 120Vac, some appliances, such as well pumps, require 240Vac.

What’s the most popular size we sell? 4kW followed by 8kW. Different models and brands are available in various sizes and most of them can be stacked together for higher power output.

Consider Pure Sine Wave Instead of Modified Sine Wave

You may hear some manufactures talk about pure sine wave inverters. You don’t need to understand exactly how these work—it’s enough to know that the power that’s put out by a pure sine wave inverter is “cleaner” than what you’d get from a modified sine wave inverter.

Pure sine wave inverters deliver higher quality power output, similar to (or better than) our power grid. Modified sine wave inverters are cheaper, but they deliver lower-quality power output.

For this reason, modified sine wave inverters can cause issues with certain appliances. Motors, pumps and compressors run hotter and wear out more quickly. Certain sensitive appliances like computers can be damaged, or they may not work at all. These inverters also typically cause background noise on a stereo, and reduced video and audio quality for certain TVs.

That’s why we don’t recommend modified sine wave inverters for most applications; most of our off-grid customers are use pure sine wave inverters to avoid these potential issues.

Need a quick way to tell the difference? Look at your inverter’s total harmonic distortion (THD) rating. THD is an indicator of power quality output and will be listed on the spec sheet of any decent inverter.

Look at the Technical Specs

Here are some other technical specs to consider:

  • Efficiency. This is a measure of how much power from the batteries your inverter delivers to your home when it’s operating in perfect conditions. A good peak efficiency rating is around 94% to 96%.
  • Self-consumption, or no-load current draw. How much power will your inverter consume just sitting there? Obviously you want this to be as low as possible.
  • Surge capacity. How much short-term overload can the inverter handle before it “trips?” Some appliances, like pumps or fridges, need as much as 2x–3x their running power to start up.
  • Battery charger output. Many off-grid inverters include a battery charger, which is used to recharge your batteries during the winter months with a backup generator. The battery charger will have a rating, usually measured in amps. Most decent off-grid inverters will have a battery charger in the range of 50-100 amps DC.
  • Temperature range. Inverters are sensitive to extreme heat. Pay careful attention to the temperature range if you plan on installing your system in your garage or anywhere it could be exposed to temperature extremes.
  • Warranty. Warranties start at 1 year and typically range from 3-5 years, with a few manufacturers offering a 10 year warranty extension option.

You can normally find information on all these features on the product spec sheets. Check with your solar tech for help comparing and picking the right inverter.

Research Features

Your inverter may need special features. Look into these ones:

  • Battery charger. A charger allows your system to be charged from a backup AC generator. Most bigger inverters include this; these are called “inverter/chargers.”
  • Grid-tied capability. Some off-grid inverters have the added capability of feeding power into the grid, here are a few examples:
    • Outback FXR/VFXR
    • Outback Radian
    • Schneider XW+
    • SMA Sunny Island

    This capability is useful if the grid becomes available in the future, or if you are setting up a grid-tied system with battery backup.

  • Automatic generator start. Usually you’ll need an add-on accessory for this, although some inverters or charge controllers can take care of it.

Read Up on the Manufacturer

Knowing about the inverter manufacturer is also important. Check into their history and reputation. Off-grid inverters need to be on all day, 365 days a year, for several years at a time—so you’ll want to choose one from a manufacturer with a reputation for reliability.

In our experience, there are only a handful of companies making high quality inverters for this purpose:

Make Sure it Has UL Listings and Certifications

Off-grid inverters have a few different certifications required in the US, for safety and also to ensure code compliance.

Inverters for your home need to be UL 1741 listed. Mobile inverters for boats and RVs should carry a UL 458 certification. There are a few other requirements for different applications such as UL 1778 for uninterruptible power supplies and KKK-A-1822E standard for emergency services, such as ambulances.

There are other standards required outside of the US such as CSA 107.1 in Canada and IEEE 1547 used internationally outside of North America.

Don't Forget Price!

You also need to look at the price of the inverter system (including all required components)—as well as the features you get for that price.

Make sure to compare the price of all required components, including the remote control, circuit breakers, mounting plate, and anything else required to install the system.

Another Good Option: Using a Pre-Wired Power Center

A power center is a pre-wired off-grid inverter system that includes everything you need: an inverter, charge controller, remote control, and circuit breakers.

Most of the power centers we sell also include some additional components for monitoring and protection, including a battery monitor, and surge suppressors.

We assemble power centers with all of these components, and then wire them up and test on our workbench to make sure the system is wired correctly and working.

Buyers, especially those looking to DIY, love power centers because you can add them to a solar installation by making only a few final connections. (We even label the connection points to help make it even easier.)

So... What's the Best Off-Grid Inverter?

Your choice of inverter really depends on your size requirements and the application, but here are some of our favorites:

Our Pick For: Best Small Off-Grid Inverter

Morningstar SureSine

  • 300 watts 120Vac output
  • 12Vdc battery bank

This inverter is small. At just 300 watts of output power, it can handle lights, charging phones and tablets, and an efficient TV—and that’s about it.

But the SureSine is renowned for being extremely durable. It’s also used for industrial applications, powering remote equipment in harsh conditions all over the world.

It’s efficient, with very low self-consumption, which makes it ideal for smaller systems like a hunting cabin.

It’s also perfect for industrial remote power systems that require a small amount of 120Vac power.

Our Pick For: Best Off-Grid Inverter for Cabins & Small Homes

Magnum Energy MS-PAE

  • Two models: MS4024PAE and MS4448PAE
  • 4kW-4.4kW 120/240Vac output
  • 24-volt or 48-volt battery bank

The MS-PAE inverter series comes in two sizes: 4kW 24-volt, or 4.4kW 48-volt.

Magnum Energy inverters are fairly easy to set up and use. They have good surge capability and powerful battery chargers. They also have a nice Magnum Panel system that includes a back plate and breaker panel (to make a complete power center).

Installing these inverters on a Magnum Panel bumps up the standard warranty from three years to five.

There are accessories available, including a battery monitor, automatic generator start (AGS) and MagWeb kit for remote monitoring.
MS-PAE Magnum Power centers have been our best selling power centers for years, both for off-grid cabins and for small homes.

Multiple MS-PAE inverters can be stacked together—up to 4 inverters, or 17.6kW total—which makes this inverter also suitable for bigger off-grid homes.

The 4kW 24-volt model can work with smaller battery banks and solar arrays; that’s ideal for cabins.

Magnum inverters are available in a wide range of sizes, and they are relatively affordable and easy to set up, which makes them a great choice for off-grid cabins and homes.

Our Pick For: Best Large Off-Grid Inverter

Schneider Electric XW+

The XW+ inverter comes in two sizes: 5.5kW or 6.8kW output power. Both work with a 48-volt battery bank.

Multiple inverters can be stacked together, and groups of three can be combined for three-phase power systems.

Schneider offers several accessories including a power distribution panel, automatic generator start, and battery monitor. The Schneider XW+ system really excels with bigger, multi-inverter systems.

Schneider supports multiple clusters of inverters for large industrial and commercial applications, up to 102kW output power. They also support Lithium batteries.

All of these features, plus the ability to stack clusters of inverters, make the XW+ our choice for large off-grid power requirements.

BONUS PICK! Best Inverter for Grid-Tied Systems with Battery Backup

Outback Power Radian

The Outback Radian is an off-grid inverter that can also tie into the grid to sell your excess power.

This is the ideal option if you want the combination of battery backup and grid-tied solar, or if you’re off-grid but you think access to the grid will become available in the future.

The Radian inverter system includes advanced software, called Optics RE, for remote monitoring and control, allowing you to monitor your system, get alerts about any faults, and change settings remotely. It can also control generators for basic automatic start and stop.

Currently this is the only battery-based inverter approved for grid-tied interconnection throughout the US. It’s also the only grid-tied battery backup inverter available that complies with the newest standards in CA and HI for connecting grid-tied systems.

It’s available in two sizes, 4kW or 8kW, and multiple inverters can be stacked together for up to 80kW of power.

This is our best selling inverter for grid-tied with battery backup; most customers opt for either one or two of the 8kW inverters (either 8kW or 16kW.)

Click to download our guide to getting started with solar power
Say Hello to the Next Generation of Grid-Tied Solar Power Inverters

Say Hello to the Next Generation of Grid-Tied Solar Power Inverters

Every grid-tied solar power system needs an inverter, and there are a lot of different ones on the market. Today we’ll help you narrow down your choice, because we’re focusing on the best of the bunch: the HD Wave Inverter from SolarEdge.

SolarEdge’s HD Wave is one of the most innovative grid-tied inverters on the market today: 50% smaller than most inverters and with an efficiency rating of 99%. It sports a number of improvements over traditional inverters, and SolarEdge spent a lot of time developing it to be the next leap forward in the industry – likened to the jump from “fat-backed” televisions to flat-screen plasma displays: it’s a huge innovation.

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But before we dive into the details of the HD Wave and what makes it so great; let’s take a look at why the inverter plays such an important role in a Solar System setup.

Why do we need an inverter anyways?

The inverter is the “brain” of your solar system. It manages your power flow, taking the DC power produced by the solar panels and “inverting” its current into AC power for your appliances and home electricity.

DC power is “unidirectional,” meaning it flows in one direction. This is what your solar panels produce when they convert the sun’s heat and light into electricity.

AC power “alternates” by changing the direction of the power flow periodically. This is the type of energy your home uses to power its appliances and devices.  

The more efficient your inverter is, the more you can take advantage of the sun’s energy, and the HD Wave Inverter is currently the most efficient grid-tied inverter on the market.


SolarEdge Leads the Pack for Innovation

This revolutionary new grid-tied inverter doesn’t come without a fair share of competition. There are hundreds of other inverter manufacturers in the world, so SolarEdge had to truly change the game in order for their design to come out on top.

SolarEdge’s innovations proved so revolutionary, in fact, that they were awarded the Intersolar Award in 2016. This prestigious award is granted to companies deemed instrumental in driving forward progress in the solar industry.

The HD Wave Inverter is not only more efficient, but it’s also considered to be one of the most reliable systems on the market. SolarEdge stands by their new technology by providing lifetime system monitoring services and a 12-year standard warranty.


6 Reasons Why the HD Wave is the New Gold Standard for Inverters:

  1. Smaller and lighter for easy installation. The small form factor of the HD Wave Inverter makes it easy for DIY installers. It weighs less than 25 lbs (regular inverters weigh much more, 50-100 lbs!).  
  2. Rated at 99% efficiency by the California Energy Commission (CEC). Most traditional inverters, when converting DC to AC, will lose 3-5% efficiency. But the HD Wave Inverter only loses 1%—allowing your system to produce more energy on average. Improvements include:
    • New digital processing technology
    • 16x less magnetics than other inverters
    • Newly optimized capacitors that improve power output.
  3. The SafeDC System: Limits each panel’s output to 1 volt. (discharging capacitors and shutting down power optimizers). This makes it safe for installers, firefighters, and maintenance personnel who are working on or around your panels.
  4. Four-button touch panel interface on the front of the HD Wave allows for smooth operation. This allows for easy setup and adjustment of your system.
  5. 12-year standard warranty ensures the system holds up over time, and can be repaired or replaced. This can be upgraded to a 20 or 25 year warranty for added peace of mind.
  6. Lifetime system monitoring (household energy consumption & production app) – sign into your SolarEdge account and keep track of your system diagnostics, PV panel performance and power flow from your computer or phone. You can even track faults or issues that crop up in real time, so you can make repairs and adjustments as soon as possible.

The SolarEdge HD Wave Inverter is available for most solar systems, sized at 3.8kW, 5kW, 6kW, and 7.6kW Watt modules, with 10kW and 11.4kW sizes coming soon, allowing it to be used for most grid-tied solar power systems.

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Solar-Powered Airplane on Round-the-World Flight

Solar-Powered Airplane on Round-the-World Flight

Screen Shot 2015-06-30 at 2.18.33 PMThe Solar Impulse, a solar-powered airplane currently circumnavigating the globe, is now almost halfway between Japan and Hawaii on a 120-hour segment. Once it reaches Hawaii, it’ll have completed the longest leg of its 22,000-mile journey across the world — all on solar power! Progress is updated in real-time, with a live video feed, on their website:

Screen Shot 2015-06-30 at 2.20.47 PM

Charging by day and running off battery power at night, pilots Bertrand Piccard and André Borschberg take turns at the helm. A variety of systems monitor everything from avionics to solar equipment to the pilots’ food, water, and oxygen rations.

Read More Read More

Sale: Racking free or half off. Free Shipping on RV Solar Kits.

Sale: Racking free or half off. Free Shipping on RV Solar Kits.

Pre-summer Solar Racking SaleNow through the June 20th, Wholesale Solar is offering some amazing deals. If you’re shopping for a solar power system on or off the grid, roof mounts are free and ground mounts are half off when you purchase systems $5,000 and up.  Roof racks normally start at $70 per solar panel, so you’ll be saving thousands of dollars.

To take advantage of the racking sale, see Wholesale Solar’s  Grid-tie,  Off-grid Systems, and Gridtie Systems with Battery Backup.

Free Shipping on Solar RV Kits. Now through June 20. Also through June 20th, Wholesale Solar is offering free shipping on their RV Solar Kits.



Texas: Money for nothin’, Power for free.

Texas: Money for nothin’, Power for free.

In Texas, utility solar incentives are generous! If you compare them to the cost per watt for a solar power grid-tied system, you’ll see that some incentives will literally pay for an entire system. Wholesale Solar’s Gridtied Solar Power Systems range from $1.30 to $2.40 per watt. While rebates and incentives in Texas range from $0.75 to $2.50 per watt, the Federal Tax Credit covers about 30% of the cost. Do the math!

Texans, research your rebates here.

93 Cents Per Watt Sale – The Best Sale So Far This Year

93 Cents Per Watt Sale – The Best Sale So Far This Year

93 cents per watt sale on black-framed 245-watt solar panels.
Quality black-framed ET solar panels on sale.

ET Solar 245-watt polycrystalline ET-P660245B solar panels are now available for 93 cents per watt when you buy a pallet of 26. Complete pallets are available at $5,924.00. Single panels are available at $258.

This ET-660245B solar panel is one of the best out in the solar market right now. Photon’s international performance test proves it.  ET 660 series solar outperformed other named brand polycrystalline solar panels in like conditions.

These panels also have the more sought after black frames.

Read more about this solar panel.

Green Gifts for the Holidays

Green Gifts for the Holidays

Holiday Gift IdeasDo you want to see how solar works first hand or teach the basics of solar to your kids? Are you looking for a useful, affordable and fun gift for someone you know? Check out these solar-powered shed lights, desk lamps and lanterns with 1.5 watts to 10-watt solar panels. They range from $25 to $170.

If you’re looking for a gift for someone who is really ready to get started with solar, check out this  solar starter kit for grid-tied applications. You’ll also be interested in small off-grid solar packages or RV/Boat kits.

Here’s Wholesale Solar’s list of gift ideas.