Solar Panel Calculator for Spokane, WA
Estimate the cost, savings and payback of solar panels in Spokane, WA, using local NREL sunshine data, Washington prices and electricity rates.
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Spokane gets about 4.44 peak sun hours a day on a south-facing roof, so each kW of panels makes about 1,257 kWh a year. That ranks #93 of the 111 cities on this site. Output peaks in Jul and is lowest in Dec.
Sunshine in Spokane by month
What an 8 kW system makes in Spokane
| Month | Sun hours a day | Output | Bill savings |
|---|---|---|---|
| Jan | 1.54 | 320 kWh | $46 |
| Feb | 2.75 | 504 kWh | $73 |
| Mar | 3.95 | 792 kWh | $114 |
| Apr | 5.53 | 1,048 kWh | $151 |
| May | 6.25 | 1,184 kWh | $171 |
| Jun | 6.38 | 1,144 kWh | $165 |
| Jul | 7.71 | 1,416 kWh | $204 |
| Aug | 6.72 | 1,248 kWh | $180 |
| Sep | 5.49 | 1,000 kWh | $144 |
| Oct | 3.58 | 712 kWh | $103 |
| Nov | 1.88 | 368 kWh | $53 |
| Dec | 1.49 | 312 kWh | $45 |
| Year | 4.44 | 10,056 kWh | $1,450 |
Savings at 14.42¢ per kWh (Washington average), with every kWh credited at that price.
Cost and payback by system size
At $2.47 per watt, the Washington average, before incentives.
| System | Cost | Year 1 savings | Payback | 25-yr gain |
|---|---|---|---|---|
| 4 kW | $9,880 | $725 | 14.1 yrs | $7,199 |
| 6 kW | $14,820 | $1,088 | 14.1 yrs | $10,798 |
| 8 kW | $19,760 | $1,450 | 14.1 yrs | $14,398 |
| 10 kW | $24,700 | $1,813 | 14.1 yrs | $17,997 |
| 12 kW | $29,640 | $2,175 | 14.1 yrs | $21,597 |
How many panels you need in Spokane
| Monthly use | System | 400 W panels |
|---|---|---|
| 500 kWh | 4.77 kW | 12 |
| 750 kWh | 7.16 kW | 18 |
| 1,000 kWh | 9.55 kW | 24 |
| 1,500 kWh | 14.32 kW | 36 |
| 2,000 kWh | 19.09 kW | 48 |
Covering 100% of a year's use at 1,257 kWh per kW.
Common questions
Is solar worth it in Spokane?
At local averages an 8 kW system costs about $19,760 before incentives, saves about $1,450 in its first year and pays back in about 14.1 years.
How many peak sun hours does Spokane get?
About 4.44 a day over the year on a south-facing roof at 20°, from 1.5 in Dec to 7.7 in Jul, according to NREL's PVWatts model.
How much does a 1 kW solar system produce in Spokane?
About 1,257 kWh a year, or 105 kWh a month on average.
Is there a federal solar tax credit?
Not for homeowners who buy their system. The 30% Residential Clean Energy Credit ended for systems installed after December 31, 2025.
Sources
- NREL PVWatts V8 API (south-facing, 20° tilt, 14% losses, typical-year weather): https://developer.nlr.gov/docs/solar/pvwatts/v8/
- EnergySage, Solar panel cost by state (updated November 6, 2026): https://www.energysage.com/local-data/solar-panel-cost/
- U.S. EIA, Electric Power Monthly, Table 5.6.B (residential price, Jan–Aug 2026): https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_5_6_b