25-year savings projection for Washington
This projection starts from Washington's assumed $0.12/kWh electricity rate and 1,050 kWh/kW of annual production, then grows savings by 3% a year as electricity prices rise and reduces output by 0.5% a year as panels degrade.
| Year | Annual savings | Cumulative savings | vs. $24,000 cost |
|---|---|---|---|
| Year 1 | $831 | $831 | −$23,169 |
| Year 5 | $916 | $4,365 | −$19,635 |
| Year 10 | $1,036 | $9,299 | −$14,701 |
| Year 15 | $1,171 | $14,878 | −$9,122 |
| Year 20 | $1,324 | $21,185 | −$2,815 |
| Year 25 | $1,497 | $28,316 | +$4,316 |
A simple, undiscounted projection — it does not apply a discount rate, financing interest, inverter replacement (commonly needed once in 25 years), maintenance, or any change in home value. Treat it as a shape, not a forecast. See methodology.
Why savings look like this in Washington
Cheap hydro power and cloudy winters are a tough combination; the sales tax exemption and retail netting help.
The single biggest variable is what your utility pays for exported power. Washington requires retail-rate net metering with annual true-up (credits zeroed each spring) for systems up to 100 kW at most utilities.
What would change this number
- Your actual rate. This uses a $0.12/kWh Washington average. If you pay more, savings scale up roughly proportionally.
- Self-consumption. We assume 68% of output is used on site at retail value and the rest exported at 45% of retail. Households home during the day, or with a battery, do better.
- Electricity price growth. At 3% a year, savings nearly double by year 25. Slower growth meaningfully reduces lifetime return.
- Incentives. Washington's main program — sales tax exemption on qualifying systems — reduces net cost and shortens break-even. See Washington incentives →
- Financing. A cash purchase earns the return above. A loan shifts it — interest can consume a large share of lifetime savings.
Frequently asked questions
How much can you save with solar panels in Washington?
An 8 kW system in Washington could save roughly $831 in the first year — about $69 a month — and around $28,316 across 25 years, assuming electricity prices rise 3% a year and panel output declines 0.5% a year. Against a midpoint installed cost of $24,000, that is a net gain of about $4,316.
What is the ROI on solar panels in Washington?
On these assumptions, roughly 18% over a 25-year system life — $4,316 of net savings on a $24,000 system. That is a simple, undiscounted return: it ignores financing interest, the time value of money, and any effect on home resale value. A cash purchase and a loan produce very different numbers.
How long does it take for solar to pay for itself in Washington?
Around year 23, when cumulative savings first exceed the $24,000 installed cost. A simple payback that ignores rising electricity prices gives a wider range of 25–33 years.
Do solar savings in Washington include the federal tax credit?
No. The 30% federal residential clean energy credit (Section 25D) ended for systems installed after December 31, 2025, so none of these figures include it. Any savings projection you see elsewhere that still applies 30% to a 2026 purchase is overstating the return.
What most affects solar savings in Washington?
Three things, in order: your utility's export compensation (Washington requires retail-rate net metering with annual true-up (credits zeroed each spring) for systems up to 100 kW at most utilities.), how much of the output your household consumes on site rather than exporting, and your actual electricity rate versus the 0.12/kWh state assumption used here. Sales tax exemption on qualifying systems can improve the result further.
Where these numbers come from
State assumptions are informed by public data and reviewed periodically (September 2026):