☀SolarAssessments.com

Solar Estimator for WA & OR Homes

How much solar fits your roof, what it could make in a year, and a rough payback. Free, sourced, no sign-up.

Is solar worth a look on your roof? Pick the city closest to you, tell us about your roof and your power bill, and you'll get a ballpark: how big a system fits, how much power it could make in a year, and a rough simple payback.

Sun data comes from runs of PVWatts, the free solar model from the U.S. Department of Energy's national lab, made Nov. 10, 2026. Default prices come from the EIA and Berkeley Lab. Every number below can be changed, and every source is linked. Source: PVWatts

Solar estimator

Find your yearly kWh on your utility bill (many show a 12-month history). The rate defaults to your state's average residential price for August 2026 (Washington 14.63¢, Oregon 15.92¢, preliminary) and switches when you change state. Use your own bill's rate if you can. Source: EIA Electric Power Monthly, Table 5.6.A The price default is Berkeley Lab's reported median for host-owned home systems installed in 2025, about $3.60 per watt before incentives; installer medians ranged widely. Source: Berkeley Lab, U.S. Distributed Solar and Storage: 2026 Data Update

Read this first. This is a rough planning estimate, not a quote. Production numbers are from PVWatts runs for a 1 kW system at a 20° tilt with PVWatts' default 14% system losses, scaled to your size. East and west results use the east/west-to-south ratio from our Seattle runs (84% and 87%), applied to every city, so they're approximate. Roof fit uses the standard formula: size (kW) = area (m²) × 1 kW/m² × panel efficiency. Real layouts lose space to setbacks, vents and fire-code paths. Savings assume every kWh is credited at your full rate, which isn't always true (see WA & OR rules). Payback ignores incentives, financing, rate changes and panel wear.

Want a site-specific number?

Run your exact address, tilt and direction in PVWatts itself. It's free. Then get at least two written quotes and compare them to what you see here.

Handy before you call an installer

electricity usage monitor plug inSee what your appliances actually usehome energy monitorWhole-house usage, if you want real numberssolar pathfinder shade analysisCheck your roof's shadeportable solar panel kitTry solar small first: camping, sheds, RVsportable power station solar generatorBackup power for outagessolar electricity handbookPlain-English books on how home solar works

These links go to Amazon search results. As an Amazon Associate I earn from qualifying purchases.

Shop merch

Sun-and-cedar shirts and mugs are coming soon. Nothing for sale here yet.