How many solar panels do I need for my home? 2025 guide

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 of panels you’ll need depends on the size of your home and your electricity usage, but we’ll walk you through how to crunch some numbers to get a reasonable estimate. If you’ve got your electric bill handy, take note of your electricity consumption over the past year. If you don’t have that information, don’t sweat it. We’ll use a few assumptions based on national averages. Let’s break it down step by step.

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, 16 to 25 panels = 10,791 kWh / 1.1 or 1.7 / 400 W

Let's break that down a bit:

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 1.7 / 400 W

…which gives us between 16 and 25 panels in a solar array, depending on which production ratio we use (16 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 

Now that you know how many panels you need, you might be wondering how much it’ll cost you. Solar panels cost $2.56 per watt on average. All in, you’re looking at about $20,500 for an 11 kW system (the average quoted system size on EnergySage) after accounting for the 30% federal solar tax credit. 

Of course, 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—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 about a 7.2 kW system to cover its electricity needs. A comparable household in Massachusetts needs about a 10 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.

What system size do you need?

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 assumes 400 W solar panels and 1.5 production ratio.

How much electricity do you use?

Perhaps one of the most challenging aspects of sizing a solar panel system 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

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, Panasonic, and REC to get optimal output. For those atypical roofs, you might end up getting a system design like this:

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.

How big is your home?

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

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 exercise for any new solar homeowner.

Solar panel requirements for individual appliances