Washington solar calculator
Size a Washington home solar system from your electric bill — kW, panel count, roof area, true cost with no federal credit for 2026 installs, and payback.
Quick answer: At $0.147/kWh and 3.8 peak sun hours, a $200/month bill needs about 15.58 kW — 38 × 410 W panels covering ~76 m². Gross cost is ~$38,950 with no federal credit for systems installed after 2025, offsetting $2,400 a year for a ~16.2 year payback.
Your details
Ballpark, not gospel. Ballpark, not gospel. Sized at 78% real-world output with the Washington sun-hour average — confirm shading, roof angle and your utility's current net-metering status with a local installer before buying. Twelve utilities had already hit their 4% net-metering cap by January 2026, and Pacific Power has asked to close new net metering after February 1, 2027. Real savings track whether your utility still offers 1:1 retail net metering — get the terms in writing before signing.
The 30% credit ended — what changed
The residential clean energy credit (26 U.S.C. § 25D) gave homeowners a 30% credit on solar installed from 2022 through 2025. The July 2025 tax law ended it: no credit is available for property placed in service after December 31, 2025. That is why every figure on this page is ~30% higher than pre-2026 guides show. If your system went live by the end of 2025, tick the box above to see the credit applied; leased systems may still benefit because the leasing company claims the commercial credit. Source: IRS — Residential Clean Energy Credit.
Typical Washington system sizes by monthly bill
| Monthly bill | System size | Panels (410 W) | Net cost (no 2026 federal credit) | Payback |
|---|---|---|---|---|
| $100 | 7.79 kW | 19 | $19,475 | 16.2 years |
| $200 | 15.58 kW | 38 | $38,950 | 16.2 years |
| $300 | 22.96 kW | 56 | $57,400 | 15.9 years |
Computed at $0.147/kWh, 3.8 peak sun hours and $2.5/W installed, with no federal credit for 2026 installs. Run your exact bill above.
Solar in Washington: the details
Solar cost in Washington
Solar is cheap to install in Washington. The EnergySage marketplace averaged about $2.50 per watt installed in 2026, with market quotes typically landing $2.12–$2.87/W — below the $2.50–$3.50/W national band. A typical ~15.6 kW Washington system grosses around $39,000 before any incentives, with no federal credit for 2026 homeowner installs.
What moves the number: roof complexity, panel tier, and installer competition. Get at least three quotes — spreads of $0.50/W between installers are common.
Export rules: getting paid for surplus power
Washington requires 1:1 retail net metering — but the clock and the caps matter. State law (RCW 80.60) obliges utilities to offer 1:1 retail net metering for systems up to 100 kW until June 30, 2029, or until a utility hits 4% of its 1996 peak load. Twelve utilities were already past that cap by January 2026; large ones like Puget Sound Energy still honor net metering, but Pacific Power has asked to close new net metering after February 1, 2027.
Leftover credits zero out each March 31, so there is no annual banking strategy. Practical takeaway: get your utility's current net-metering terms in writing before you sign — the economics of your project hinge on locking in 1:1, and the cap is utility-specific.
Washington solar incentives
Washington's main incentive is a full sales tax exemption: systems of 1–100 kW are 100% exempt from state sales tax on equipment and installation labor.
The per-kWh Renewable Energy System Incentive Program closed to new applicants on June 30, 2021, so the tax exemption is the lever. That makes cheap rates the challenge: there is no production incentive to bridge Washington's weak sun.
Is solar worth it in Washington?
Verdict: marginal. The calculator puts a $200/month bill at a ~16.2-year payback with no federal credit — the weakest sun of any state on this page (3.8 peak hours) against middling rates is the problem. 1:1 net metering helps, but twelve utilities have already hit their caps and the statewide guarantee ends June 2029. If your utility still honors full net metering, an unshaded system can work; if not, the math falls apart. Get the terms in writing first.
Questions people actually ask
Straight answers, no fluff. Then run your own numbers above.
How many solar panels do I need in Washington?
It follows your bill. At the Washington average of $0.147/kWh and 3.8 peak sun hours, a $200/month bill needs about a 15.58 kW system — roughly 38 × 410 W panels covering ~76 m² of roof.
What is the average cost of solar panels in Washington in 2026?
Solar is cheap to install in Washington. The EnergySage marketplace averaged about $2.50 per watt installed in 2026, with market quotes typically landing $2.12–$2.87/W — below the $2.50–$3.50/W national band. A typical ~15.6 kW Washington system grosses around $39,000 before any incentives, with no federal credit for 2026 homeowner installs.
Does Washington have net metering?
Yes — for now. State law (RCW 80.60) requires 1:1 retail net metering for systems up to 100 kW until June 30, 2029 or until a utility hits 4% of its 1996 peak load. Twelve utilities were already past that cap by January 2026 (though large ones like PSE still honor it), and leftover credits zero out each March 31.
Does Washington offer any solar tax credit or rebate?
Systems of 1–100 kW are 100% exempt from state sales tax on equipment and installation labor. The per-kWh Renewable Energy System Incentive Program closed to new applicants on June 30, 2021 — so the tax exemption is the main lever.
Is the 30% federal solar tax credit still available?
Not for homeowner purchases anymore. The residential clean energy credit (26 U.S.C. § 25D) is not available for property placed in service after December 31, 2025, under the July 2025 tax law (Public Law 119-21). Systems installed by the end of 2025 can still claim 30%, and leased systems may still benefit because the leasing company claims the commercial credit instead. (Source: IRS — Residential Clean Energy Credit.)
Is solar worth it in Washington?
Verdict: marginal. The calculator puts a $200/month bill at a ~16.2-year payback with no federal credit — the weakest sun of any state on this page (3.8 peak hours) against middling rates is the problem. 1:1 net metering helps, but twelve utilities have already hit their caps and the statewide guarantee ends June 2029. If your utility still honors full net metering, an unshaded system can work; if not, the math falls apart. Get the terms in writing first.
Figures last checked October 2026. Sources: EIA Electric Power Monthly, NREL PVWatts/NSRDB, DSIRE, Washington Utilities and Transportation Commission; IRS — Residential Clean Energy Credit.
More US solar calculators
Compare other states: Texas, Florida, California, Arizona, North Carolina, South Dakota, Tennessee, Utah, Vermont, Virginia, West Virginia, Wisconsin, Wyoming. And the national US solar calculator for country averages.
Comparing quotes? The solar cost calculator breaks down cost per watt and the solar ROI calculator maps your payback year by year. Going deeper: installation cost guide, how net metering works, how much you can save with solar and the solar batteries guide.