How many solar panels do I need for my home in 2024?

A typical home in the U.S. needs between 17 and 25 solar panels to power it fully- but that number can vary significantly.

Edited by: Emily Walker
Updated Apr 24, 2024
14 min read
Home with solar panels on the roof and people inside

If you’ve shopped for solar panels, you know the process comes with some ambiguity, whether you’re asking about costs, the payback period, or the number of panels you’ll need.

The exact number you need will depend on the size of your home and your electricity usage. If you can handle a little math, some number crunching will get you to a reasonable estimate. If math isn't your strong suit, don't sweat it. We'll make it as straightforward as we can.

Before we start, you’ll need your electric bill, ideally with information about your electricity consumption over the past year. You can start with 400 watts as a placeholder for wattage per panel. If you already have a specific solar panel in mind, identify its wattage and use that number instead. Once you have those two figures, you can start working on an estimate.

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Key takeaways

  • An average home needs between 17 and 25 solar panels to fully offset utility bills with solar.

  • You can use our Solar Calculator to determine exactly how many panels you will need for your home.

  • The number of solar panels you need depends on a few key factors, including your electricity consumptiongeographic location, and individual panel specifications.

  • You'll need more solar panels for the same output if you live in Massachusetts compared to California.

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 = system size/production ratio/panel wattage

For example, 17 to 25 panels = 10,791 kWh / 1.1 or 1.6 / 400 W

Let's break that down a bit:

Calculating how many solar panels you'll need to meet your energy needs depends on several factors. The easiest way to find out how many panels you'll need is to use our Solar Calculator. When you put in your address and estimated monthly power bill, we'll do all of the math for you so that you can make an informed decision. If you'd like to do those calculations, we've explained our formula below to help.

The formula we used to estimate the number of solar panels you need to power your home depends on these critical factors. Here are the assumptions we made and how we did our math:

Annual electricity usage

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 or solar array size, which would mean you could 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.

Solar panel wattage

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 most solar panels fall in the 300 – 400+ W of power range. We'll use 400-watt panels in these calculations because 390-400 W is the most quoted capacity range on the EnergySage Marketplace, according to our latest Intel Report.

Production ratios

A solar panel system's production ratio is its estimated energy output over time (kWh) to its actual system size (W). These numbers are rarely 1:1 – depending on how many hours of sunlight your system will get (primarily based on your geographic location), your production ratio will change accordingly. 

For example, a 10 kW system that produces 14 kWh of electricity in a year has a production ratio of 1.4 (14/10 = 1.4) – this is an entirely realistic production ratio to see out in the real world. In the U.S., production ratios are usually between 1.1 and 1.6, so we'll use those two numbers as the high and low estimates for our calculation.

See the average production ratio in your state based on quotes from EnergySage installers

Now, let's work out the math

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, as shown above:

Number of panels = system size/production ratio/panel wattage

Plugging our numbers in from above, we get the following:

Number of panels = 10,791 kWh / 1.1 or 1.6 / 400 W

…which gives us between 17 and 25 panels in a solar array, depending on which production ratio we use (17 for a 1.6 ratio and 25 for a 1.1 ratio). If we use California as an example (average production ratio of 1.5), you'll need about 18 panels, resulting in a system size of 7.2 kW.

Solar panel cost 

There is a consideration for how many solar panels to buy without including cost. Solar panels cost $2.86/W on average. The total average cost of an installation is $22,022 for an 11 kW system (the average quoted system size on EnergySage) after accounting for the 30% federal solar tax credit. This varies widely depending on location, installation cost, and incentives, with warmer climates being cheaper but needing more panels and vice versa for colder climates.

Calculating how many solar panels you need can be done with the three inputs above, but digging deeper, many more factors are at play 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.

How much solar power can your panels produce? 

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. But in either location, you'll be able to produce enough power to cover your energy needs and say goodbye to your utility bills.

If you live in an area with fewer peak sunlight hours, you'll need a more extensive solar array system installed at your home. Thus, production ratios differ according to geographic location, and a lower production ratio (because of less sunlight) means you'll need more solar panels to get the amount of energy production you need.

Here's an example: as mentioned above, two comparably sized households in California and Massachusetts consume the average amount of electricity for an American household, which is 10,791 kWh annually. As we calculated earlier, the California household needs about a 7.2 kW system to cover its electricity needs. A comparable household in Massachusetts needs about a 10 kW system.

Solar panel systems in California are smaller than in Massachusetts but can produce the same amount of power because they're exposed to more peak sunlight hours each year. In less sunny areas like Massachusetts, you can make up for this disparity by using more efficient panels or increasing the size of your solar energy system, resulting in slightly more solar panels on your rooftop.

How many solar panels do you need for specific system sizes?

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.

Number of solar panels needed for specific system sizes

System Size
Number Of Panels Needed
Estimated Annual Production
4 kW106,000 kWh
6 kW159,000 kWh
8 kW2012,000 kWh
10 kW2515,000 kWh
12 kW3018,000 kWh
14 kW3521,000 kWh

The table above again assumes that you're using 400 W solar panels, and your production ratio is 1.5. However, the number of panels you need to power your home and the amount of space your system will take up on your roof will change if you use lower-efficiency panels or high-efficiency panels (which generally correlates to low and high power rating, respectively).

Perhaps one of the most challenging aspects of sizing a solar panel array is estimating your household's annual energy usage. Several more oversized consumer products or add-ons can significantly change your annual kWh requirements and greatly 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.

How much roof space do you have?

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.

Square footage of different sized solar panel systems

System Size
300 W Panels (sq. Feet)
340 W Panels (sq. Feet)
360 W Panels (sq. Feet)
400 W Panels (sq. Feet)
4 kW234207195176
6 kW351310293264
8 kW468413390351
10 kW585517489439
12 kW702620585527
14 kW819723683615

If your home is small or has an unusually shaped roof, the power output and efficiency of your solar panels are important to consider. If you have 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 Panasonic, SunPower, and REC, to get optimal output. For those atypical roofs, you might end up getting a system design like this:

Solar panels designed on a roofMany solar panel companies like SunPower 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.

How does your home size affect the number of solar panels you need?

Check out the table below for a ballpark estimate of how many solar panels your home would need based on its square footage (assuming 400 W solar panels and a production ratio of 1.5).

Home square footage compared to the number of solar panels needed

Home Size
Estimated Annual Electricity Needed
Number Of Solar Panels Needed
1,000 sq. feet4,710 kWh8
2,000 sq. feet9,420 kWh16
2,500 sq. feet11,775 kWh20
3,000 sq. feet14,130 kWh24

How many solar panels do you need for common appliances?

Reviewing the various kWh requirements for everyday household appliances and products, one thing is clear: specific add-ons will dramatically change 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 energy system. 

It's certainly possible to install a solar 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 like 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 habit for any new solar homeowner.

Solar panel requirements for individual appliances

Product
Average Annual Electricity Needed
Number Of Solar Panels Needed
Refrigerator600 kWh1
Window air conditioning215 kWh1
Central air conditioning1,000 kWh2
Electric vehicle3,000 kWh5
Heated swimming pool2,500 kWh5
Hot tub (outdoor)3,300 kWh6
Check out our comprehensive home solar guide

The best way to understand how many solar panels you need is to get multiple quotes. When you use the free EnergySage Marketplace, we'll gather custom quotes for your home. Have questions? Book time with one of our expert Energy Advisors, who will help walk you through the process.

Find out what solar panels cost in your area in 2024
Please enter a five-digit zip code.
  • 100% free to use, 100% online
  • Access the lowest prices from installers near you
  • Unbiased Energy Advisors ready to help
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