Solar panels in Washington: payback, production and savings

In Seattle, each kW of south-facing panels produces about 1,088 kWh a year, #50 of 51 states for sunshine. Homes in Washington paid 14.71¢/kWh on average in July 2026 (#39 highest in the U.S.; national average 18.31¢), up 9.4% from a year earlier. Below-average power prices stretch the payback, so sizing and the export credit matter more.

Output by month (kWh per kW)

Jul is the best month (143 kWh) and Dec the weakest (33 kWh).

Example: 7 kW system, 10,500 kWh/yr home

	Full net metering	Credit ½ retail	Credit ¼ retail
Year-1 savings	$1,120	$848	$712
Payback	17.2 years	21.8 years	25.0 years
25-year net gain	$12,327	$4,135	$39

Assumptions, not quotes: $21,000 installed ($3,000/kW), no incentives, 40% of use during daylight, power prices +2.5%/yr. Change them below.

How roof direction changes output in Washington

kWh per kW per year, and the difference vs. south at 20°.

Facing	20° pitch	30° pitch
South	1,088 (+0%)	1,115 (+2%)
Southeast	1,032 (-5%)	1,039 (-4%)
Southwest	1,054 (-3%)	1,070 (-2%)
East	912 (-16%)	876 (-19%)
West	943 (-13%)	917 (-16%)
East-west (split)	927 (-15%)	897 (-18%)

What to check before going solar in Washington

How your utility credits exports. Net metering rules differ by state and by utility, and several states have moved to lower "net billing" credits worth a fraction of the retail rate. The example table shows three cases; look up your utility's current program in the DSIRE database.
Federal tax credit. The 30% residential clean energy credit does not apply to systems placed in service after December 31, 2025 (IRS). Count only state or utility incentives that are still open.
Your real price per kWh. Divide your bill's energy and delivery charges by the kWh used; fixed monthly fees don't go away with solar.

Run your own numbers in Washington

Your roofLocation

FacingRoof pitch

System sizekWA typical modern panel is 0.4 kW.

Your usageAnnual electricity usekWh/yrAdd up 12 months of bills. U.S. homes average roughly 10,000–11,000 kWh.Use while the sun is up%30–40% if nobody is home during the day; 50–60% if you work from home.

PricesElectricity price$/kWhBlank = Washington average from EIA ($0.147/kWh). Use your bill's all-in rate.Credit for exported powerInstalled cost$/kWYour quote divided by system size. Example value.Rebates and incentives$The 30% federal credit ended for systems placed in service after Dec 31, 2025.

Advanced

Maintenance & insurance$/yrElectricity price change%/yrAssumption. Try 0% for a conservative case.

First-year savings

$1,120

Payback

17.2 years

25-year net gain

$12,327

Return (IRR)

3.6%

Production vs. use by month

7,616 kWh/yr produced · covers 37% of your use directly · 51% of output used on the spot.

Production Use

Which size pays off best?

Same usage and prices, only size changes. Best 25-year net gain: 10 kW.

kW	Cost	Year-1 savings	Payback	25-yr gain
3	$9,000	$480	18.9 years	$3,854
4	$12,000	$640	18.1 years	$5,972
5	$15,000	$800	17.7 years	$8,091
6	$18,000	$960	17.4 years	$10,209
7	$21,000	$1,120	17.2 years	$12,327
8	$24,000	$1,280	17.1 years	$14,445
10	$30,000	$1,545	17.0 years	$18,444
12	$36,000	$1,545	19.4 years	$14,258

Estimate based on NLR PVWatts and EIA data. See the methodology.

States with similar sunshine

Data: NLR PVWatts v8 (U.S. DOE National Laboratory of the Rockies, formerly NREL), TMY weather for Seattle (47.61, -122.33), 14% losses, retrieved 2026-10-11. Prices: U.S. EIA Electric Power Monthly, Table 5.6.A (July 2026). Methodology.