How Much Roof Space Do I Need to Support a Solar System?

By Erin Wallace

July 05, 2025

The idea of solar panels sounds good to you, but maybe you're not sure where to start. You know they should probably go on your roof for the most sun exposure, but how do you know how much roof space you need for solar panels? Get the answers to all your solar panel-related questions below.

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How Much Roof Space is Needed to Install Solar Panels?

The number of panels you need depends on what your electricity needs are — do you plan on relying only on solar panels for electricity, or are they being used to supplement your power usage? The number of panels you install will dictate how much roof space you need.

Solar panel installers help you customize a system that takes into account your energy usage, roof space and budget. According to Palmetto Solar, a solar company based in North Carolina, one solar panel has the potential to generate an average of 15 watts of solar energy. Keep in mind this number varies by location, sun exposure and solar panel type.

If you live in a small home, you might only need around 200 square feet of roof space for solar panels, but a larger home might need 1,000 square feet or more. Palmetto estimates the average American home might need 18 to 24 solar panels to offset the average amount of energy usage. But again, this varies by location and your household's energy usage and rates.

How Many Solar Panels Can Fit on My Roof?

The average size for a residential solar panel is about 5.5 feet by 3 feet. These panels typically have 60-70 individual cells. Knowing the area of one solar panel can help you figure out if your roof is big enough to hold 18 of them.

In addition, websites such as solar-estimate.org provide resources to help you evaluate solar panel needs based on your location and potential cost savings.

Calculating Roof Space for Solar Panels

Palmetto provides an easy way to calculate how many solar panels your roof can potentially fit. First, multiply the total square footage of your roof by 0.75. You can't use the entire square footage of your roof to estimate how many panels will fit because there has to be an edge border around the solar panel array. Some professionals call this the solar panel setback. An open space is needed between the edge of the panels and the edge of the roof for safety reasons and to comply with local and state building codes. The specifics vary by location, but in general, the solar panel setback accounts for around 25% of the usable space for panels.

Take this number and divide it by 17.5. This is the average square footage of a standard residential solar panel.

The resulting number is an estimate of the maximum amount of solar panels that can fit on your roof.

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Can Solar Panels Be Installed on Any Kind of Roof?

The U.S. Department of Energy states that solar panels work best on south-facing roofs that have a slope between 15 and 40 degrees. They can be installed on most kinds of roof materials, including asphalt shingles and metal. You may need special supports or reinforcements, depending on the age and condition of your home and roof.

If you're thinking about installing solar panels to help you save money on electricity or to be a bit more environmentally conscious, many online resources and solar panel installers can help you estimate the benefits for your area and how many solar panels your roof is able to support.

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