In Washington, a 10.6-kW system for an average home costs about $26,294 after incentives in 2026, saves about $1,635 in the first year and pays back in 13.7 years.
| Item | Amount |
|---|---|
| Solar, 10.56 kW × $2.49/W | $26,294 |
| Federal credit (0%) | $0 |
| Net cost | $26,294 |
| Scenario | Net cost | Year-1 savings | Payback | 25-yr net |
|---|---|---|---|---|
| State averages (above) | $26,294 | $1,635 | 13.7 yr | $29,611 |
| Rates rise 5.6%/yr (2020–25 pace) | $26,294 | $1,635 | 12.1 yr | $52,214 |
| Rates stay flat | $26,294 | $1,635 | 16.7 yr | $12,333 |
| Survey price $3/W (LBNL) | $31,680 | $1,635 | 16 yr | $24,225 |
| Add 13.5-kWh battery | $43,615 | $1,635 | 20.7 yr | $12,290 |
| Exports cut to 50% of retail | $18,625 | $813 | 18.4 yr | $9,097 |
Verdict: at average Washington numbers, solar is a marginal investment in 2026 — payback takes 13.7 years, leaving you $29,611 ahead after 25 years. The main reasons: weak sun (the 2nd-lowest yield of 51); 1:1 net metering, which credits every exported kWh at the full retail price. Get at least three quotes: every $0.25/W you shave off the price moves payback by roughly a year or more here.
Net metering and exports in Washington: Full retail net metering; credits reset each March 31 (Grays Harbor PUD pays 50% retail).
Battery: a 13.5-kWh battery at the Washington average of $1,283/kWh adds $17,321 and saves almost nothing extra under 1:1 net metering — buy it for backup, not payback; payback becomes 20.7 years.
EnergySage's Washington page lists a 15.4-year payback. Its method is not fully published; ours uses EIA's Jan–Aug 2026 price, 1:1 net metering, 3%/yr rate growth and 0.5%/yr panel aging, with no federal credit.
The full method, material data and tips are on the main solar payback calculator page.