How Many Solar Panels in Washington?
A typical Washington household using 10,500 kWh a year needs about 25 panels — a 10.0 kW system. That is 5 more than the national average.
Panels needed
25
50 of 51 states, fewest first
System size
10.0 kW
Roof space
450 sq ft
Peak sun hours
3.6 / day
Based on 400W panels and 10,500 kWh a year. Your own bill will differ — put your figure into the calculator.
What drives the number in Washington
At 3.6 peak sun hours a day, Washington is one of the less sunny states. Each kilowatt delivers about 1,051 kWh a year, so a system here has to be noticeably larger than a southern one to cover the same usage, which is the main reason upfront cost is higher.
Roof space is usually the binding constraint rather than budget. The 450 square feet above is usable south-facing area — chimneys, vents, dormers and north-facing slopes do not count towards it.
How long would that system take to pay for itself in Washington? →