How many solar panels do I need for my home in 2023?

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. For that last one, a good rule of thumb is that a typical home in the U.S. needs between 15 and 25 solar panels to power it fully. 

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.

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. 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 10,632 kWh of electricity per year (or 886 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 percent 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 anywhere from 1.1 to 1.7, so we'll use those two numbers as the high and low estimates for our calculation.

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:

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

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

Number of panels = 10,632 kWh / 1.1 or 1.7 / 400 W

…which gives us between 15 and 25 panels in a solar array, depending on which production ratio we use (15 for a 1.7 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 $2.95/W on average. The total average cost of an installation is $20,650 for a 10 kW system (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 10,632 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 9.6 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?

In our extended example at the beginning of this piece, 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

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 size solar panel systems

If your home is small or has an unusually shaped roof, the size of solar panels can be very important to consider. While those with a large roof may sacrifice some efficiency and buy larger panels to achieve the ideal energy output, homeowners with a smaller roof must be able to use fewer small high-efficiency panels – like those from SunPower, LG, or REC – to get optimal output. For those atypical roofs, you might end up getting a system design like this:

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

While solar panel dimensions have more or less remained steady over the past several years, the power output within the same area has dramatically increased. Many manufacturers like SunPower have 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 400 W solar panels and a production ratio of 1.7).

Home square footage compared to the number of solar panels needed

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; however, it should be planned accordingly, considering it could double the size of your solar energy system. 

Though it's certainly possible to install a solar system and then have a solar installer add more panels later to accommodate increased energy needs, the most pragmatic option is to size your system as accurately as possible based on your expected purchases – such as an electric vehicle, swimming pool or central air system. 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

Do you still have an electricity bill with solar panels?

Once you install solar panels, you'll still receive a monthly electricity bill. However, it should be lower, close to zero, or even negative! If you're still experiencing high utility bills after installing solar panels, you may need to reconsider the size of your system. Especially if you have added electricity loads since your solar installation (like an electric car), your current system size might not cut it anymore.

The only situation in which you won't have an electricity bill is if you choose to go off-grid by installing a solar battery – but in most cases, it's better to keep your solar energy system grid-tied, even if you add battery storage.

Are there disadvantages to powering a home with solar panels?

The two main disadvantages of solar energy are the high upfront costs and intermittency, meaning that solar energy isn't available 24/7 because the sun doesn't shine at night. Luckily, that problem can be partially sorted with battery storage. Check out our article about the advantages and disadvantages of renewable energy to learn more.

Are solar panels worth it?

Solar panels are worth installing depending on your electricity prices, how much electricity you consume, your desire to be eco-friendly, and your home's geographic location. While the initial investment in solar panels is high, they pay off over time by cutting down your electricity bills. On average, EnergySage solar shoppers "break-even" on their solar investment in about eight to nine years. And, as solar deployment continues to grow (reducing cost) and inflation rates rise further, solar will likely become even more worth it.

How can you calculate how many solar panels you need?

You can find 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.

There are multiple variables to consider when seeking out the best solar panels. While some panels will have higher efficiency ratings than others, investing in top-of-the-line solar equipment doesn't always result in higher savings on your utility bills. The only way to find your property's "sweet spot" is to evaluate quotes with varying equipment and financing offers. Check out our quote comparison platform if you want quotes from local contractors today.