How Many Solar Panels Do I Need?
Enter your monthly usage or bill to find your panel count, system size, and roof space.
Calculate your panel count
Your solar panel results
Panels needed by monthly usage
Same sun hours and panel wattage as your settings above. Your usage level is highlighted.
How to work out how many solar panels you need
This free calculator finds how many solar panels your home needs from your monthly electricity use, your local sun, and the wattage of each panel. It is for homeowners planning a system or checking an installer quote. It is free, needs no sign-up, and runs entirely in your browser.
How many solar panels do I need?
It depends on how much electricity you use, how much sun your roof gets, and how powerful each panel is. Divide your monthly usage by 30 to get daily use, then divide by peak sun hours to find system size in kilowatts. Divide that size by panel wattage to get the panel count. This calculator does all three steps.
The Solar Energy Industries Association reported that the United States passed 5 million solar installations in 2024, so panel counts like these are now an everyday question for millions of homeowners, not a niche one.
What are peak sun hours?
Peak sun hours measure how much usable sunlight a location gets in a day, counted as hours of full strength sun. Most of the United States gets between 3.5 and 5.5 peak sun hours a day, with the sunny south west at the high end. This calculator uses 4.5 by default, so change it to match your area.
You can find your local figure from your installer, from a solar map, or from your utility. A home in Arizona may get 5.5 or more, while a home in Seattle may get under 4, and that difference changes the panel count by several panels.
How much roof space do solar panels need?
A standard home panel is about 17 to 18 square feet, so 17 panels need about 306 square feet of roof, plus walking space around the edges. Roof direction matters as much as size, because a south facing roof in the northern hemisphere catches the most sun. Shade from trees or chimneys can cut output sharply, so check it first.
What size solar system do I need in kilowatts?
A home using 900 kilowatt hours a month needs about a 6.7 kilowatt system in an area with 4.5 peak sun hours, which is about 17 panels at 400 watts each. Smaller homes using 500 kilowatt hours need about 3.7 kilowatts, or 10 panels. Use the table above to compare system sizes at different monthly usage levels.
Most home systems fall between 4 and 10 kilowatts. Oversizing a little can help if you plan to buy an electric car or a heat pump later, but a system far bigger than your usage wastes money, because exported power is often paid at a low rate.
Do I need a battery as well?
A battery is optional for most homes, because panels already cut your bill during the day, and a grid connection covers the night. A battery helps if you want backup power during outages or your utility pays little for exported electricity. Batteries add several thousand dollars, so size your panels first, then decide about storage separately.
- Grid connected, no battery. Cheapest option, and the right choice for most homes with reliable power.
- With battery. Worth it for backup power, frequent outages, or low export payments.
- Off grid. Needs a much larger system and battery bank, plus a generator for dull spells.
Frequently asked questions
How many solar panels do I need for a 2,000 square foot home?
It depends on usage, not floor area. A typical home using about 900 kWh a month needs about 17 panels at 400 watts in an area with 4.5 peak sun hours. Enter your real usage above for your own count.
How many panels do I need to run my whole house?
Enough panels to cover your monthly usage, which for most homes is 15 to 25 panels at 400 watts each. Homes with electric heating, air conditioning, or an electric car need more, so check your last 12 months of bills for the true figure.
What wattage are most home solar panels?
Most new home panels are 370 to 450 watts, and 400 watts is a common size. Higher wattage panels mean fewer panels for the same system size, which helps on a small roof.
How do I find my monthly electricity usage?
Look at your electricity bill, which usually shows kilowatt hours used that month, or check your utility online account. For the best estimate, average 12 months of usage, because summer and winter use can differ a lot.
Can I put solar panels on a small roof?
Often yes. Higher wattage panels, such as 450 watt models, pack more power into the same space. If the roof is still too small, a smaller system that covers part of your usage can still be worth it.
Do I need more panels in winter?
No, you size for the yearly average, not for winter alone. Panels produce less in winter, but most homes use less power then too, and yearly net metering balances the seasons. Sizing for the darkest month would oversize the system.
Does this calculator store my data?
No. The calculator runs entirely in your browser. Nothing you type is uploaded, stored, or shared.
More tools you may need
Want the cost of that system? Use the Solar Panel Cost Calculator. Wondering when it pays for itself? Try the Solar Payback Period Calculator. Planning storage or a bigger system? See the Solar Battery Size Calculator and the Solar System Size Calculator.
