Solar panels in Washington, DC

Roofs in Washington get about 1,562 hours of usable sunlight a year — more than 59% of the cities we've measured. Here's what that means in cost, savings and payback, using real rooftop data rather than a national average.

Check your specific roof in Washington → City averages are a starting point; your own roof's size, pitch and shading change the answer a lot.

What a typical Washington solar system costs

A 21-panel system (8.4 kW) is about right for an average Washington home using 10,800 kWh a year. It would produce roughly 11,153 kWh annually and offset 100% of that usage.

How we worked this out for Washington

Every number on this page comes from these seven steps. Nothing is a national average — the sunlight figure is measured from Washington rooftops.

Step 6 matters more than it looks. Only 34% of what a system this size produces in Washington is used the moment it is generated; the other 7,373 kWh is exported and credited one-for-one under net metering. Because exports here are credited at or near retail, that split changes the payback very little — 8.6 years against the 8.8 we show. In places where exports pay a fraction of retail the same split moves payback by years, which is why we model it explicitly rather than assuming.

Assumptions: 400W panels, 15% system losses (inverter, wiring, heat, soiling), $2.85/W installed, 10,800 kWh typical annual household use, 17.4¢/kWh electricity. Change any of those and every figure above moves — which is exactly why a single national "solar costs X" number is misleading.

Notice that payback barely improves as systems get bigger, and eventually gets worse. That's because you can only save money on electricity you were going to buy anyway. Once a system covers your usage, extra panels mostly generate exports at a much lower rate.

Why Washington gets 1,562 sun hours

That figure comes from Google's analysis of real rooftops across Washington — it already accounts for shading from trees, chimneys and neighbouring buildings, which is why it's lower than the raw "hours of daylight" figures you'll see elsewhere. An unusually open, unshaded roof in Washington reaches about 1,613 hours, roughly 3% better than typical.

The numbers behind this page

When Washington actually produces

Annual totals hide the thing that catches people out: 36% of Washington's yearly sunlight arrives in May–July, and just 14% across November–January.

Washington produces about 2.9× as much in Jun as in Dec — a normal mid-latitude swing. Expect real winter shortfall and summer surplus rather than steady year-round output.

The annual total is measured from Google's rooftop imagery. Its split across months is calculated from solar geometry at Washington's latitude, not separately measured, so treat the monthly figures as the shape of a typical year rather than a forecast.

How Washington compares to the other 788 cities

What actually stands out about Washington:

• Older imagery. Google's aerial capture of Washington dates from 2014. Tree growth and new construction since then are not reflected.

Cities with almost the same sunlight

These are the closest matches to Washington's 1,562 usable sun hours from other states and provinces. Same sunlight, different electricity prices — which is usually what decides whether solar is worth it.

Nearby cities

Washington solar questions

Worth reading before you buy

Estimates only, generated 2026-08-22 from Google Solar API rooftop samples and average DC electricity rates. Not a quote and not financial advice. Your roof, usage, utility plan and local incentives will change these numbers — get real quotes before buying.