How Many Solar Panels Are Needed to Run a House?

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Solar panels (Photo: @Inspired_by_the_Seasons via Twenty20)
If you want your home to leave the smallest carbon footprint possible or don’t have access to the electrical grid, solar panels offer a fantastic solution. By using an atomic reaction from sunlight in photovoltaic cells to generate a flow of electricity, solar energy can be used to operate a home’s appliances and other electrical devices.
To completely offset a home’s power needs, how many solar panels are required? Here’s what you need to know about determining your home’s solar array.

Factors affecting how many solar panels your home needs

There are a few factors that come into play when calculating your home’s solar panel system, whether variable or a fixed factor:
Your location. Whether you live in sunny California or in overcast New York makes a difference for your solar needs. The more direct sunlight on your solar panels during the day, the more electricity they can generate. Location isn’t something you can change, really.
Exposure to the sun. A home that has a roof that’s shaded for most of the day reaps little benefit from solar panels, while a fully exposed roof section can harvest much more energy. In North America, southern exposure is the most common and efficient placement, but it’s not the only option.
Panel efficiency. There are three levels of efficiency among solar panels: low-, medium-, and high-efficiency. A system with high-efficiency panels requires fewer panels than a low- or medium-efficiency system, but that usually comes with higher upfront costs.
Your home’s average consumption. How many panels you need mostly has to do with how much power your home consumes. Lower consumption requires fewer panels and vice versa.

Average home power consumption

To get an estimate on how much power you need to produce to power a whole home, it helps to understand the average homeowner’s energy consumption. Although it varies a lot from state to state, an average American home uses 877 kWh of energy monthly. That means that, in a year, an average home will consume just over 10,500 kWh of electricity.

Calculate the number of solar panels you would need

Calculating the number of solar panels you need to power a home is a math equation. To start, you’ll need your home’s electricity usage from the previous year. Calculations will assume annual consumption of 10,000 kWh.
Medium-efficiency panels produce around 310 watts per hour, and in the course of a day produce around 1.24 kWh. High-efficiency panels make about 20% more while low-efficiency produce about 30% less.
Divide 10,000 kWh by 365 days to determine a per-day production requirement. Rounded up, it is 28 kWh per day. To power a whole home at 100% of your daily consumption, divide 28 kWh by 1.24 kWh to find out how many panels you need. Rounded up, it’s 23 panels.
Since homes are obviously different sizes and locations around the country experience varying amounts of daylight, the average home in the U.S. will need between 22 and 34 panels to fully offset its electrical consumption.

Can you operate a home on just solar power?

Many solar panel arrays store energy for later use in battery banks, making it possible to use electricity even after the sun goes down. Physically, it’s possible to operate a home completely on solar energy. However, if you have a mortgage, most of the major mortgage investors like Freddie Mac, VA, and Fannie Mae require that you have an alternate energy source connected to your home.
That’s a good idea for peace of mind, but also it’s possible to sell excess electricity back to your local power provider if you’re connected, potentially even making a little money off the system.