How many solar panels do I need?
Updated
The amount of solar panels your home needs depends on the amount of energy your home needs, as well as the efficiency of your panels.
A typical American home will need 14-36 solar panels to cover their power bill and at least 227 square feet of rooftop space to accommodate solar panels.
The amount of energy that solar panels can absorb, and then produce, is measured in kilowatts (kW). The amount of energy your home uses over a certain timeframe, say a month, is measured in kilowatt hours (kWh).
You need to know how many kWh your home uses to determine the amount of kW your solar panels need to produce to offset your use. You can also use this information to determine the number of panels your home will need.
In this blog, we will review the factors that solar installers take into account when recommending how many solar panels you need for your home.
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What factors determine the number of solar panels your house needs?
Interestingly, your home size does not actually determine the amount of solar panels you need; a bigger home does not equal more energy consumption.
To really understand how many solar panels your solar energy system needs, you need to determine:
- The amount of energy your home uses: Look at monthly kWh used on your electric bill
- The direction of your roof: Southern-facing roofs receive more sunlight in the northern hemisphere
- The average amount of sunlight in your local area: Put more simply, the southwest gets the most sun in the United States, versus the northeast which gets some sun but with more rain and snow mixed in
- The amount of wattage, or energy, the solar panel you purchase can produce: Solar installers can help you determine your options
To get a quick answer, you can use the solar panel calculator immediately below to give you an exact number of solar panels your home needs. Or, follow along to calculate the amount yourself!
How many solar panels offset electricity use of 1,000 kWh per month?
According to the U.S. Energy Information Administration, in 2019 the average monthly electricity consumption for a home in the United States was 877 kWh per month, or about 29.23 kWh per day and 10,649 kWh per year.
Knowing the U.S. electrical use average is a helpful starting point but each home is unique, follow the steps below to figure out how your home compares to the average.
How to calculate the number of solar panels you need for your home
Step 1: Determine how much electricity your home uses
Check out your most recent electricity bill to see your monthly kWh use. With most bills, the total kWh of electricity you used will be shown at the bottom with the cost of electricity multiplied by that amount.
In the above example, you can see that over the month, 290 kWh were used. Each utility multiplies the kWh by various charges to cover the cost of delivering the electricity to your home.
In this example, that charge adds up to a monthly total of $40.94. But, the average American home uses 877 kWh a month, which would make this bill cost about $115.
Step 2: Determine if your roof is southern-facing with no tree blockage
Every household is different and could use more or less power than the average home. Other factors that can determine solar panel effectiveness are roof direction, shade, and the climate where you live.
If you have a southern-facing roof with no shade, move on to Step 3. But if your roof is shaded or your home does not face south, working with a solar installer can help you determine the best location for your solar panels.
Step 3: How much sunlight does your area receive?
The solar system size your home needs will depend on your electricity consumption and the climate of your region. To help you better estimate the potential size solar array your home will need, the below chart can provide a little more clarity.
| Average annual electricity usage for all homes | Solar system size needed to produce average electricity | Amount of solar panels needed | |
|---|---|---|---|
| West - California | 6,384 kWh | 4 kW | 14 |
| Northeast - New Jersey | 7,956 kWh | 7 kW | 25 |
| Midwest - Illinois | 8,508 kWh | 7 kW | 25 |
| South - Texas | 13,680 kWh | 10 kW | 36 |
| *280 watt solar panels |
This table breaks down the average annual electricity usage for each region in the US. The four states listed, California, New Jersey, Illinois, and Texas offer some of the best solar incentives for their respective regions.
In Column 2, we listed the solar system size that would be needed in each region to offset a homeowner’s average electricity usage. For example, to cover the energy needs of a typical California home, you would need a 4kW solar power system to generate 6,384 kWh of electricity.
The numbers vary mostly because of the climate of each region. You need a smaller system in Southern California because the sun shines all year long, but you need a larger system in New Jersey because there are more cloudy days and the winter months to consider.
Last, in Column 3, we listed the number of 280-watt panels that would be needed to produce the necessary electricity.
However, your home’s energy use could be totally different than the average. You can use our solar panels cost calculator to work out how much the number of solar panels quoted in the table above for your state will cost.
How much roof space do I need for solar panels?
Once you determine your electricity consumption, your roof direction, and your climate, it is time for Step 4 - choosing the efficiency rating of the solar panels that makes sense for you.
Step 4: What wattage solar panel is best?
Even if you know the amount of solar panels you need, it won’t help if your roof can’t fit them. In the chart below, we break down the square feet your rooftop would need for a 5kW, 10kW, and 15kW system.
| System size | Square footage needed for low efficiency (16%) | Square footage needed for medium efficiency (18%) | Square footage needed for high efficiency (22%) |
|---|---|---|---|
| 5 kW | 313 | 278 | 227 |
| 10 kW | 625 | 556 | 455 |
| 15 kW | 938 | 833 | 682 |
We calculated the amount of square footage needed based on the potential efficiency of panels you would purchase. We used the typical efficiency range of 16%, 18%, and 22% for low, medium, and high-efficiency solar panels.
Solar panel efficiency essentially means that your solar panel is either okay, good, or great at absorbing sunlight for energy production. Higher efficiency panels means you need less of them, and in turn, less square footage of roof space in order to produce energy.
Once you determine the kW size of the solar panel system you need, take a look at the amount of space a low, medium or high-efficiency panel will take up on your roof. If you have extra space to spare, it might make sense to buy lower efficiency panels since they are cheaper than higher efficiency and can produce the same amount of electricity.
Determining which efficiency-level solar panel makes sense for your home will depend on the amount of space you have. In order to make sure your roof has enough space, find out here.
Do solar panels make sense for my home?
Ultimately, most homes' roof space should be able to accommodate solar panels that will cover their energy usage. Working with a professional solar installer can help you determine the best-sized solar system for your energy needs. Check out our calculator to get in touch with top-rated installers in your area or check out local installer reviews.
Key takeaways
- The average American home needs 14-36 solar panels to cover their electricity bill.
- If you live in a sunnier state, less solar panels are needed to generate the electricity your home needs.
- More efficient solar panels means less solar panels are needed.
- High efficiency panels are necessary when installing solar panels on a small roof.
Author: Ana Almerini | Web Content Specialist
Ana is a web content specialist at SolarReviews. She has 5 years of marketing experience blended with 2 years of experience in climate communications and holds a master of arts degree in climate and society from Columbia University. Ana frequently volunteers for environmental causes ranging from oyster reef restoration in NJ to expanding bike sharing in Naples, Italy.