In the United States, the average home consumes about 10,400 kilowatt-hours (KhW) of electricity each year. Assuming a given solar panel produces 250 watts of power, you’d need 28 to 34 of them to meet your annual electricity requirements. But do you consider your home “average”? Whether you do or not, other factors besides panel capacity may affect how many solar panels you need.

The number of solar panels needed to fully offset a grid-based electricity bill varies from home to home. To determine the exact number of panels needed, first you must determine the system size in kilowatts (kW). Some examples include:

3.5kW: 14 panels

5kW: 20 panels

10kW: 40 panels

12kW: 48 panels

15kW: 69 panels

Next you need to determine how many panels will fit on your roof. Not only do you need to factor in square footage, but also the efficiency of the panels you use. For a 5kW system, you’ll need 306 square feet of low efficiency panels or 224 square feet of high efficiency ones. For a larger 15 kW system, you’ll need 918 square feet of low efficiency and 672 square feet of high efficiency panels.

LOCATION MATTERS

Solar panel production ratio varies by location. The highest in the U.S. is 1.31, which is in Arizona, while the lowest is in Maine, where the solar panel production ratio is 1.61. The more sun a solar panel is exposed to, the more power it can produce. In California, for example, there are more sunny days per year than in New England, but that doesn’t mean you can’t benefit from solar power in Massachusetts.

In California and Massachusetts, two comparably sized homes consume around 10,400 kWh of electricity per year. California’s smaller solar panel systems don’t make them less efficient. That’s because the state gets more sunlight per year. Here, a 7.0kW system can cover all a home’s energy needs. A home in Massachusetts requires an 8.8kW system, but less sun can be compensated for with larger solar energy systems and more efficient panels.

That also means in the Northeast, more solar panels are needed to get as much electricity.

NUMBER OF SOLAR PANELS VS. HOME APPLIANCES

The number of panels you need is also affected by how power is consumed in your home. Based on annual energy consumption in kilowatt-hours, a refrigerator requires at least two solar panels. You’ll need three panels for central air conditioning and 10 to keep your electric vehicle charged. A heated swimming pool requires eight panels to run while an outdoor hot tub requires 11 solar panels to meet its annual power requirements.

HOW TO FIGURE OUT HOW MANY SOLAR PANELS YOUR HOME NEEDS

To determine exactly how many panels to install, you need to consider:

• Your home’s energy usage over an entire year, as indicated on your utility bill.
• How many kilowatt-hours you get per kilowatt of solar power (as determined by location and climate)
• How many will fit on your roof (less are needed for an unshaded, south-facing roof)

Also take note that California has rules for a 3-foot setback, so firefighters can access parts of the roof in case of an emergency.

GO SOLAR WITH SOLAR4AMERICA

If you’re uncertain about how many solar panels to install, consult with PetersenDean’s professional designers and project managers. Our multi-certified installers can maximize the solar power produced by installing the right number of panels, while working within your budget. Call 888-893-5222 to consult with our Solar4America experts or request an estimate online today.