Solar Calculators for Seattle, Washington

Free tools with illustrative Seattle planning inputs. Replace energy rates and installation costs with your bill and written quote.

Quick answer

Start with your exact utility account and roof design. The 3.5 sun hours and 10.0 cents/kWh below are planning assumptions, not verified current rates for Seattle. Confirm Seattle City Light / PSE eligibility and export settlement.

Notes updated 2026-07-26

Best for: Seattle homeowners comparing a proposal or estimating savings before calling installers.
Inputs needed: 12-month kWh usage, roof shade, Seattle City Light / PSE, quoted $/W
Formula used: Local production = system kW × local peak sun hours × 365, then adjusted for losses.
Method references: NREL PVWatts, Seattle City Light / PSE, Washington incentive rules

Peak sun hours

3.5

hrs/day planning assumption

Illustrative energy rate

10.0¢

per kWh (Seattle City Light / PSE)

Typical install cost

$2.85/W

planning assumption, not a market median

Net metering policy: Full retail net metering ✓

What Seattle homeowners should check

Seattle solar produces strongly during long summer days but much less through cloudy winter months. Evergreen shading, moss, roof drainage, and the remaining life of older roofing can materially affect usable production.

Seattle City Light and Puget Sound Energy serve different addresses and maintain separate application processes. Verify the utility and use annual production, not a sunny-month snapshot, when comparing proposals.

At the state level, Washington currently uses full retail net metering (engrossed senate bill 5116). A typical interconnection takes 4–10 weeks, but utility review and local permitting can extend that range. Check current rules before relying on a proposal's export-credit or installation-date assumptions.

What should I verify before signing a solar contract in Seattle?

Confirm that the quote names your actual utility, uses a recent electricity rate, includes measured shade and roof-condition findings, and explains who handles permits and interconnection. Ask the installer to separate guaranteed equipment and workmanship terms from estimated production, incentives, and savings.

Illustrative 8 kW system in Seattle

Annual production

8,781 kWh

Retail-value ceiling

$878

System cost (est.)

$22,800

Energy-only cost/value ratio

~26 yrs

Illustrative 3.5 peak sun hours, 14.08% production losses, 10.0 cents/kWh and $2.85/W. The retail-value ceiling assumes every kWh earns retail value; lower export credits reduce it. The cost/value ratio is not a full payback model and excludes repairs, financing and rate changes. No new Section 25D homeowner credit in 2026.