A worked example: 8 kW in Washington
An 8 kW system — about 19 × 425-watt panels — at Washington's assumed installed cost of $2.60–$3.40 per watt runs roughly $20,800–$27,200 before incentives. At about 1,050 kWh of production per installed kW, it would generate around 8,400 kWh per year. Valuing self-consumed electricity at the assumed $0.12/kWh retail rate and exports conservatively, first-year savings land near $831 — a simple payback of roughly 25–33 years.
There is no federal tax credit in that math: the Section 25D residential credit ended for systems installed after December 31, 2025. State or utility incentives, where they exist, would shorten payback from here.
Average cost of solar panels in Washington by system size
Most Washington quotes land between 6 and 12 kW. At the state's assumed $2.60–$3.40 per watt, here is what each size costs to install, what it produces, and how long it takes to pay for itself on electricity savings alone — no incentives applied.
| System size | Panels | Installed cost | Annual production | Est. payback |
|---|---|---|---|---|
| 6 kW | 15 | $15,600–$20,400 | 6,300 kWh | 25–33 yrs |
| 8 kW | 19 | $20,800–$27,200 | 8,400 kWh | 25–33 yrs |
| 10 kW | 24 | $26,000–$34,000 | 10,500 kWh | 25–33 yrs |
| 12 kW | 29 | $31,200–$40,800 | 12,600 kWh | 25–33 yrs |
Size should follow your electricity usage, not a round number — these are reference points, not a recommendation. Note that cost per watt rises on smaller systems, because permitting, labor and the inverter do not shrink with the array.
What solar costs per kWh in Washington
Spread across a 25-year life, with 0.5%/yr panel degradation and no financing cost, solar electricity in Washington works out to roughly 10.5¢–13.7¢ per kilowatt-hour. The Washington retail rate this page assumes is 12.0¢. That gap — not the sticker price — is what determines whether solar pays here, and it is why a sunnier state with cheap electricity can be a worse investment than a cloudier one with expensive electricity. See how every state compares on cost per kWh.
Net metering and export rates in Washington
Washington requires retail-rate net metering with annual true-up (credits zeroed each spring) for systems up to 100 kW at most utilities.
Export rules are worth reading as an incentive, because they set what every kilowatt-hour you do not use on site is worth — see how Washington compares with every other state on net metering.
Washington solar incentives
Washington exempts qualifying residential solar systems from sales tax — significant given the rate — but offers no current state production incentive for new customers.
The most valuable program is sales tax exemption on qualifying systems. With no federal credit for 2026 installs, state and utility programs are now the whole picture — see the full Washington incentives guide.
Solar costs in Washington cities
Statewide averages blend climates, utilities and installer markets that differ within Washington. These city guides use local production factors and name the specific utility serving the area.
What changes a Washington solar quote?
Equipment, roof condition, electrical upgrades, permitting, labor, system size, batteries and financing can all change the installed price. Savings also depend on the specific utility rate, how much solar electricity the home uses directly, and what the utility pays for exports.
Frequently asked questions
What is the average cost of solar panels in Washington?
The average installed cost in Washington runs $2.60–$3.40 per watt before incentives, which puts a 6 kW system at $15,600–$20,400, an 8 kW at $20,800–$27,200, and a 10 kW at $26,000–$34,000. Spread over a 25-year life, that works out to about 10.5¢–13.7¢ per kilowatt-hour, against a Washington retail rate assumed at 12.0¢.
How much does it cost to install solar panels in Washington?
Installation is not priced separately — the $2.60–$3.40 per watt above is a turnkey figure covering panels, inverter, racking, labor, permitting and interconnection. What moves it most in WA is roof complexity, whether the main panel needs upgrading, and whether a battery is included. Expect a site visit to change any online estimate, including this one.
How much do solar panels cost in Washington?
Using an assumed installed cost of $2.60–$3.40 per watt, a typical 8 kW home system in Washington costs roughly $20,800–$27,200 before incentives. Smaller and larger systems scale roughly with size, though small systems cost more per watt.
Is solar worth it in Washington?
With Washington electricity around $0.12/kWh and production around 1,050 kWh per installed kW per year, an 8 kW system could save roughly $831 in year one, for a simple payback of about 25–33 years with no federal credit. Whether that is "worth it" depends on your rate plan, export compensation, roof, and how long you plan to stay in the home.
How many solar panels do I need in Washington?
It depends on your electricity usage, not your roof. At Washington's assumed 1,050 kWh per installed kW, a 6 kW system (about 15 panels at 425 watts) generates roughly 6,300 kWh a year, and a 10 kW system (about 24 panels) roughly 10,500 kWh. Compare that against your annual kWh from a utility bill — our calculator sizes it from your monthly bill in about a minute.
Does Washington have net metering?
Washington requires retail-rate net metering with annual true-up (credits zeroed each spring) for systems up to 100 kW at most utilities.
What solar incentives does Washington offer in 2026?
Washington exempts qualifying residential solar systems from sales tax — significant given the rate — but offers no current state production incentive for new customers. Note that the federal Section 25D residential credit ended for systems installed after December 31, 2025, so state, local and utility programs are now the main incentives for purchased systems.
Is there still a federal solar tax credit in Washington?
No — the 30% federal residential clean energy credit (Section 25D) ended for systems installed after December 31, 2025 under the One Big Beautiful Bill Act. Leased or PPA systems may still benefit indirectly because the system owner can claim the commercial 48E credit through 2027.
Use this as a starting point
This page provides broad state assumptions, not a current market survey or binding quote. Before purchasing, verify applicable incentives, utility rules, installer licensing, warranties and financing terms.
Where these numbers come from
State assumptions are informed by public data and reviewed periodically (September 2026):