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EnergySage Releases 21st Solar & Storage Marketplace Report
How much do solar panels cost?
Most homes need 15-22 solar panels to ditch their electric bill. Here's how to figure out your magic number.
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Staring at your electric bill and wondering how many solar panels it would take to make it disappear? You're not alone. It's one of the first questions every homeowner asks when they start thinking about going solar. The answer is simpler than you might think.
The truth is, there's no one-size-fits-all answer. Even if your houses look identical from the street, your neighbor might need 18 panels while you need 22. Your electricity usage, roof space, and location all play starring roles in this calculation.
The good news? You don't need an engineering degree to figure this out. We'll walk you through a straightforward calculation that gets you a solid estimate using just your electric bill and a few basics about your home. If you have your electric bill handy, that'll give you the most accurate starting point. If not, we'll use national averages to get you in the ballpark.
Ready to crunch some numbers and see what solar independence looks like for you?
Most homeowners save around $50,000 over 25 years
An average home needs between 15 and 22 solar panels to fully offset utility bills with solar
The number of solar panels you need depends on a few key factors, including your electricity consumption, geographic location, and individual panel specifications
If math isn't your thing, you can use our Solar Calculator to determine exactly how many panels you will need for your home
You can calculate how many solar panels you need by dividing your yearly electricity usage by your area's production ratio and then dividing that number by the power output of your solar panels.
To put it simply:
Number of panels = annual electricity usage / production ratio / panel wattage
For example, 15 to 22 panels = 10,791 kWh / 1.1 or 1.7 / 450 W
Let's break that down a bit:
Your annual electricity usage is the energy you use in your home over a year. Measured in kilowatt-hours (kWh), this number is influenced by the appliances in your home that use electricity and how often you use them. Refrigerators, air conditioning units, small kitchen appliances, lights, chargers, and more all use electricity.
According to the U.S. Energy Information Administration (EIA), the average American household uses 10,791 kWh of electricity per year (or about 900 kWh per month), so we'll use that number as the ideal solar panel system size. We're assuming you'd offset 100% of your electricity usage and utility bill with solar panels (in practice, it's not this neat, but bear with us here).
To get a more exact number based on how much energy you use, check last year's electric bills to determine your average electricity consumption. Once you have that number, plug it into the equations below.
Also known as a solar panel's power rating, panel wattage is the electricity output of a specific solar panel under ideal conditions. Wattage is measured in watts (W), and 97% of solar panels fall in the 400+ W power range in 2025. We'll use 450-watt panels in these calculations because it’s the most quoted solar panel size on EnergySage.
A solar panel system's production ratio is its estimated energy output over time (kWh) relative to its actual system size (W). These numbers are rarely one-to-one: Production ratios vary according to how many hours of sunlight your system will get (primarily based on your geographic location).
For example, a 10 kW system that produces 15 MWh (15,000 kWh) of electricity in a year has a production ratio of 1.5 (15/10 = 1.5). In the U.S., production ratios are usually between 1.1 and 1.7, so we'll use those two numbers as the high and low estimates for our calculation.
We have our three main assumptions (energy use, solar panel wattage, and production ratios)—so how do those numbers translate to an estimated number of solar panels for your home? The formula looks like this:
Number of panels = annual electricity usage / production ratio / panel wattage
Plugging our numbers in from above, we get:
Number of panels = 10,791 kWh / 1.1 or 1.7 / 450 W
…which gives us between 15 and 22 panels in a solar panel system, depending on which production ratio we use (15 for a 1.7 ratio and 22 for a 1.1 ratio). If we use California as an example (average production ratio of 1.5), you'll need about 16 panels, resulting in a system size of 7.2 kW.
Now that you know how many panels you need, you might be wondering about cost. On average, solar panels cost $2.53 per watt. For a 12 kW system (the average quoted system size on EnergySage), you're looking at about $29,649 before any available incentives.
Of course, solar costs vary widely depending on location, installation cost, and availability of state and local incentives.
Calculating how many solar panels you need can be done with the three inputs above, but digging deeper reveals many more factors in determining your ideal solar panel system size. Understanding production ratios, the relationship between system size and the number of panels, and the impact of home size can all be meaningful when designing your ideal solar panel setup.
The amount of power (kWh) your solar energy system can produce depends on how much sunlight your roof receives, which creates your production ratio. The sunlight you get in a year depends on where you are in the country and the time of year.
For instance, California has more sunny days annually than Massachusetts, so you'll need a bigger solar panel system to produce the same amount of energy. But in either location, you'll be able to produce enough power to cover your energy needs and say goodbye to your utility bills.
Here's an example: Two households, one in California and one in Massachusetts, use the average amount of electricity, 10,791 kWh, annually. As we calculated earlier, the California household needs a 7.2 kW system to cover its electricity needs. A comparable household in Massachusetts needs a 9.9 kW system.
So, in less sunny areas like Massachusetts, you might consider choosing highly efficient solar panels to maximize your energy output per square foot.
We determined that a 7.2 kW system would probably cover the average energy use for an American household if you live in an area with a production ratio of 1.5, which might be a realistic number for homes in most parts of California.
Let's extend that further and look at a few more examples. In the table below, we've compiled some solar panel number estimates for common solar system sizes seen on the EnergySage Marketplace. Again, the big caveat is that we're using 1.5 as the production ratio of choice. This might be realistic for California shoppers, but for folks in the Northeast or areas with less sun, these estimates might be a bit high on the production end and low on the number of panels needed.
The table above assumes 450 W solar panels and 1.5 production ratio.
Perhaps one of the most challenging aspects of sizing a solar panel system is estimating your household's annual energy usage. Larger consumer products or add-ons can significantly change your annual kWh requirements and impact how many panels you will need.
For example, if you're running central air conditioning or powering a heated swimming pool in your backyard, the size of your solar panel array could be drastically altered. To get a feel for the size you'll need, you should evaluate the energy impact of various products you own or are considering for your home.
Ultimately, you'll only be able to install as many panels as you can fit on your roof. Below is a table that will give you a sense of how many square feet your system will take up on your roof, depending on the power output of the solar panels you select.
The table above assumes solar panel dimensions of 5.5 feet by 3 feet.
If your home is small or has an unusually shaped roof, the power output and efficiency of your solar panels are especially important to consider. With a large roof, you can probably choose less efficient solar panels because you have more space for more panels. But if you have a smaller roof, we recommend choosing more power-dense, high-efficiency panels, like those from Maxeon, Qcells, Solarever, Canadian Solar, and REC, to get optimal output.
Some solar panel companies have even reduced the size of gaps between panels and use invisible framing and mounting hardware to keep the panels tight, efficient, and aesthetically pleasing.
Check out the table below for a ballpark estimate of how many solar panels your home would need based on its square footage (assuming 450 W solar panels and a production ratio of 1.5).
Reviewing the various kWh requirements for everyday household appliances and products, one thing is clear: Specific add-ons will dramatically change your monthly energy use and can impact the size of the solar panel system you should install. For example, pairing your electric vehicle with solar panels is a great way to reduce carbon emissions and improve energy efficiency. But it could double the size of your solar panel system.
It's certainly possible to install a solar panel system and then add more panels later to accommodate increased energy needs. However, it's easier and cheaper to size your system as accurately as possible based on your expected purchases such as heat pumps, an electric vehicle, or a swimming pool. Asking yourself, "How many solar panels will I need for my refrigerator, hot tub, etc." is an excellent exercise for any new solar homeowner.
The table above assumes 450 W solar panels and 1.5 production ratio.
Getting the number of panels right isn't just about covering your current electric bill—it's about building a system that works for your life today and tomorrow. Order too few panels and you'll still be paying your utility every month. Size your system too large and you'll overspend on equipment you don't need.
The beauty of solar is that once you've determined your number, your panels will continue to do the same reliable work year after year. No monthly bills to dread, no rate increases to stress about, no wondering if this month's usage will spike. Just clean electricity flowing from your roof, powering your home the way you need it to.
Whether you land on 15 panels or 22, you're making a decision that reshapes how you power your life for decades. And that calculation you just learned? It's the first step toward energy independence that actually sticks.
Most homeowners save around $50,000 over 25 years
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