Solar panels in Federal Way, WA

Roofs in Federal Way get about 1,249 hours of usable sunlight a year — less than 83% 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 Federal Way → City averages are a starting point; your own roof's size, pitch and shading change the answer a lot.

What a typical Federal Way solar system costs

A 26-panel system (10.4 kW) is about right for an average Federal Way home using 10,800 kWh a year. It would produce roughly 11,041 kWh annually and offset 100% of that usage.

How we worked this out for Federal Way

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

Step 6 matters more than it looks. Only 34% of what a system this size produces in Federal Way is used the moment it is generated; the other 7,261 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 — 16.6 years against the 16.9 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, 11.3¢/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 Federal Way gets 1,249 sun hours

That figure comes from Google's analysis of real rooftops across Federal Way — 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 Federal Way reaches about 1,327 hours, roughly 6% better than typical.

The numbers behind this page

When Federal Way actually produces

Annual totals hide the thing that catches people out: 40% of Federal Way's yearly sunlight arrives in May–July, and just 10% across November–January.

That is a severe seasonal swing — Federal Way produces roughly 4.5× as much in Jun as in Dec. A system sized to cover your annual usage will overproduce badly in summer and fall well short in winter, so how your utility credits exported power matters more here than in most places.

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

How Federal Way compares to the other 788 cities

What actually stands out about Federal Way:

• Cheap electricity is the headwind. Washington power costs about 11.3¢/kWh. Low rates are good news generally, but they lengthen solar payback — there is simply less bill to displace.

Cities with almost the same sunlight

These are the closest matches to Federal Way's 1,249 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

See all of Washington → statewide sunlight, rates, incentives and every city we've measured.

Federal Way solar questions

Worth reading before you buy

Estimates only, generated 2026-08-22 from Google Solar API rooftop samples and average Washington 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.