Solar calculator for Washington
Panels, system size, cost and payback for Washington, from your own power bill.
The average Washington home uses 956 kWh a month and pays 11.9 cents per kWh, which puts Washington at some of the cheapest electricity in the country, which stretches payback. Winter heating shapes the bill in Washington, and winter is when panels make the least, so a bill that looks big in January does not map cleanly to a bigger array. A south-facing fixed array there makes about 1,088 kWh per installed kW a year, and the worst winter month still gets 1.32 peak sun hours a day. Drop in your own bill below and the numbers on this page are replaced by yours.
A worked example for Washington
Take the average home: 956 kWh a month, which is 11,472 kWh a year, at 11.9 cents per kWh (EIA, 2024 residential averages, as of 2026-11). Sized to cover all of that use, the tool returns 10.5 kWdc and 26 panels, needing about 546 square feet of roof. The installed estimate is $26,255 (national median, EnergySage H2 2025), yearly savings are about $1,365, and simple payback is 19.2 years, with no incentive applied.
Sun and yield in Washington
We use 1,088 kWh per installed kW per year for Washington, from NREL PVWatts v8 for the state's largest city at a 20 degree south-facing tilt (via TheGreenWatt, as of 2026-11). The darkest month averages 1.32 peak sun hours a day, which matters if you plan to go off-grid or size a battery. A different roof angle or heavy shade changes this, so treat it as a starting point.
Incentives
The 30% federal tax credit ended for homeowner purchases after December 31, 2025, so none is applied here. See the tax credit guide. Look up Washington and your own utility for net metering terms and any local programs before relying on a payback number.
Planning estimate. Permits, interconnection approval and a licensed electrician are required for grid-tied systems.
Questions
How many solar panels does a Washington home need?
The average Washington home uses 11,472 kWh a year (EIA 2024). At about 1,088 kWh per installed kW, covering all of it takes 10.5 kWdc, or 26 panels. Your own bill will move that up or down.
How much does solar cost in Washington?
For the average-home example the installed estimate is $26,255 at the national median of $2.49 per watt (EnergySage, H2 2025, as of 2026-11). We have no sourced Washington price multiplier, so local quotes will differ.
Is there a federal solar tax credit in Washington?
The 30% federal tax credit ended for homeowner purchases after December 31, 2025. Check your state, utility and local programs separately.
Where does the Washington sun figure come from?
1,088 kWh per kW per year and 1.32 winter peak sun hours come from NREL PVWatts v8 runs for Washington's largest city, compiled by TheGreenWatt (as of 2026-11). Real yield varies across the state.
Is my bill uploaded?
No. Your bill is read in your browser and never uploaded.