How many solar panels are needed for an average house?

Solar panels have enjoyed a meteoric rise in popularity in recent decades. That’s thanks in part to an increase in environmentally responsible behavior and the desire to reduce energy bills by exchanging traditional sources of heating, cooling and electricity with cleaner, more natural sources. If you’re thinking of making this switch, you’re probably wondering how many solar panels it takes to power a house.

We estimate that a typical home needs between 17 and 21 solar panels to cover 100 percent of its electricity usage. To determine how many solar panels you need, you’ll need to know: your annual electricity consumption, the wattage of the solar panels you’re considering, and the estimated production ratio of your solar system. You can calculate the number of solar panels you’ll need by dividing the system size by the production ratio, and again by the panel wattage.

Factors that determine how many solar panels you need

You may think that the size of your house determines how many solar panels you need, but it doesn’t! To really understand how many solar panels your solar energy system needs, you need to determine the following: 

Your energy usage: The more electricity you use, the more solar panels you need to cover your electricity costs.

Sunlight in your area: Homes in areas that receive less sunlight will need more solar panels to eliminate their electricity bills than those in sunnier states. As a rule of thumb, the southwestern United States gets the most sun in the country, while the northeast gets the least.

Panel wattage: The wattage of the solar panels you choose, also called the power rating, determines how much energy the panels will produce and most solar panels installed today have a power rating of about 370 watts per panel; fewer panels are needed when you install panels with high wattage ratings.

How to calculate the number of solar panels you need

Our solar panel cost and savings calculator is the fastest, easiest, and most accurate way to find out how many solar panels your home needs - and you don’t have to do any math. Plus, we’ll give you the average cost of a solar installation for your specific home and how much it’ll save you on your electric bills.

However, if you want to put pen to paper and work out the calculations for yourself, follow these four easy steps to find how many solar panels you need. 

Step 1: Determine your energy usage 

Check out your most recent power bill to see your monthly electricity consumption. In most cases, the total amount of electricity used will be shown at the bottom of the bill in kilowatt-hours (kWh).

Your yearly energy usage will give you the best estimate for how many solar panels you need, as energy usage fluctuates in different seasons (think about how much electricity you use for air conditioning in the summer!). 

Because monthly energy usage varies so much, it can be beneficial to dig up your monthly electric bills for the past year, add the electric usage together, and divide by 12. 

But using just one utility bill to find your energy consumption is still enough for a ballpark estimate. 

Step 2: Find how much energy solar panels produce in your area 

Now that you know how much electricity your home uses in a month, you need to find the amount of sunlight your area receives. This is usually measured in something called "peak sun hours", which is essentially the intensity of sunlight in your area. 

We have a complete list of the average number of daily peak sun hours for each state. This is how much sunlight your area receives daily, be we need to know how much you receive monthly. To do this, simply multiply your state’s daily peak sun hours by 30. On average, the U.S. receives between 120 and 150 peak sun hours per month.

The monthly peak sun hours you get tells you how many kilowatt-hours of electricity 1 kilowatt (kW) of solar panels will produce in your area in one month. So, if your state receives 150 monthly peak sunlight hours, 1 kW of solar will produce 150 kWh of electricity per month.

Step 3: Calculate solar system size you need 

Since you now know how much 1 kW of solar will produce in your area, you can determine what size solar system you need to cover your electricity needs. 

Divide your monthly electricity usage by the monthly peak sun hours in your area to find the system size you need in kW. For the average home in the U.S. the calculation would look something like this:

893 kWh consumed / 135 monthly peak sun hours = 6.61 kW of solar

Step 4: Figure out how many solar panels you need 

So, you know the size of the solar system you need to cover your energy usage. Now what? To figure out how many solar panels you’ll need, take the solar system size and multiply it by 1,000 to convert the size from kilowatts to watts. Let’s use the same example as before: 

6.61 kW of solar x 1,000 = 6,610 watts of solar

Next, take the size of the system in watts and divide it by the wattage of the solar panels you want to install. The average solar panel in the U.S. is about 370 watts in size. For the sake of our example, that means you would need 18 solar panels to cover your energy usage.

6,610 watts of solar / 370-watt solar panel = 18 solar panels

Voila! That’s the number of solar panels you will need to power your home.

FAQ

How many solar panels does it take to power a house?

Based on average electricity consumption and peak sun hours, it takes around 17 400-Watt solar panels to power a home. However, this number will vary between 13-19 based on how much sun the panels get and how much electricity the home uses.

Use the equation below to get an estimate of how many solar panels you need to power a house.

Daily electricity consumption / peak sun hours / panel wattage = number of solar panels

Can I run my house on solar only?

Absolutely. By pairing solar panels with battery storage, it is very possible to run a house on solar power alone. And in many areas it’s cheaper than paying for electricity through a local utility.

Without battery storage, you can still offset your grid electricity use with solar panels through net metering and eliminate your electricity bill. You will still be using grid electricity when solar generation is down, but you will only pay for your solar equipment.

Is 10 kW enough to run a house?

Yes, in many cases a 10 kW solar system is more than enough to power a house. The average US household uses around 30 kWh of electricity per day, which would require 5 kW to 8.5 kW solar system (depending on sun exposure) to offset 100%.