Everyday
Solar Panel Calculator
Enter monthly electricity use and peak sun hours. The page sizes your system in panels and kilowatts, checks it against your roof area, and estimates installed cost and payback.
How it works
Behind the numbers
Sizing starts from your electric bill. Monthly kilowatt-hours become daily watt-hours, divided by peak sun hours and adjusted for 14% system losses. That gives the DC watts needed, which the calculator converts to a whole number of panels at your chosen wattage.
The roof check multiplies panel count by about 17.5 square feet per panel and compares it with your usable roof area. If the system does not fit, the page says so plainly instead of giving you a number you cannot install.
Cost uses the $2.50-$3.50 per watt installed band, and payback divides that by yearly savings from your rate. Both are ranges on purpose: real quotes move with roof, wiring, and local labor.
FAQ
Questions, answered
How many solar panels do I need?
Divide daily watt-hours by peak sun hours and system efficiency, then divide by panel wattage and round up. A home using 900 kWh a month with 5 sun hours needs about 18 four-hundred-watt panels. The calculator runs this with your numbers.
How much does solar cost per watt?
US installed averages run $2.50-$3.50 per watt before incentives. A 7 kW system lands around $18,000-$25,000. Actual quotes vary by state, roof complexity, and installer.
Is the federal solar tax credit still available?
The 30% federal residential credit expired December 31, 2025. State and utility incentives still exist in many areas; check current programs before budgeting.
How long until solar panels pay for themselves?
Divide installed cost by yearly bill savings. At $0.17 per kWh and average sun, many systems pay back in 9-14 years. The calculator shows a range based on your rate and cost band.