How much area is needed for solar panel installation

5 steps to calculate the area needed for your solar panel installation

Calculating the square footage needed for your solar installation depends on many unique project factors, which include your roof's attributes, where you live, and the specific panels you choose to install. For a quick idea of how much roof space you'll need, here are five steps you can take when calculating area for solar panels on your property.

Step 1: Determine your daily electricity usage

Going solar starts with understanding your home's electricity usage. Measured in kilowatt-hours (kWh), your annual electricity consumption can be found on your utility bills. If you divide this number by 365, you can calculate your average daily electricity usage. In the U.S., the average home consumes about 30 kWh of grid electricity per day.

Step 2: Identify the average peak sun hours in your area

Solar panels can generate electricity at the highest efficiencies during peak sun hours, which are usually in the late morning and afternoon. Across the U.S., the average property receives between 4 and 5 peak sun hours per day-though this varies greatly by region and season. You can estimate your property's daily solar radiation, and expected system output, using the PVWatts® calculator from the National Renewable Energy Laboratory.

Step 3: Calculate your ideal solar power capacity

By dividing your average daily electricity use by your property's peak sun hours (PSH), you can estimate your approximate solar energy system size. If your home consumes 30 kWh of electricity and receives 4.25 PSH per day, this will equal a solar system capacity of approximately 7 kilowatts (kW). To account for energy losses during inclement weather, this number can be multiplied by 1.2, which translates to an ideal system capacity of about 8.5 kW or 8,500 watts (W).

Step 4: Choose the number of panels you'll install

To calculate the number of solar panels you need, divide your system's total capacity by the wattage of each panel. As the average home solar panel is about 400 W, an 8.5 kW system would consist of approximately 21.25 panels. Rounding up, a 22-panel installation may be best.

Step 5: Estimate your required roof space for solar

Finally, multiply the number of solar panels by the square footage of each module. The average residential solar panel size is about 17.5 sq ft-though it's good to overestimate the area required as some installation space is necessary between the panels and rows.

When installing 22 panels like in our example, and each panel takes up about 18 sq ft, your system would require approximately 396 sq ft of roof space. If you use microinverters, this could be spread across multiple roof surfaces without compromising total system performance.