Wind Turbine Payback in King County, WA
Wind turbine payback in King County
No. The turbine wears out before it pays for itself.
At 30 m, the height a home turbine tower usually reaches, the wind in King County, WA averages 2.75 m/s (6.2 mph). A 10 kW turbine there would make about 1,920 kWh a year, worth $277 at WA's 14.42¢/kWh. Against an installed cost of about $100,000, that is a payback of over 100 years, and the turbine is built to last about 20.
What to do in King County
A home turbine is not worth buying for savings in King County unless your spot is far windier than the county average, 8.1 m/s at the hub against 2.75 m/s here. Per kW, solar panels would make about 1,098 kWh a year here against the turbine's 192, so get a solar quote first.
What would have to change
- Power would have to cost 260¢/kWh, 18.1 times what WA pays now.
- Or the average wind at the hub would have to be 8.1 m/s instead of 2.75. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of WA
King County is the 3,127th windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. The windiest in WA is Columbia County at 5.18 m/s, payback 50 years.
Month by month in King County
January is the strongest month here, at 3.81 m/s and about 480 kWh. July is the weakest, 1.76 m/s and 23 kWh, so the best month makes 20.9 times the worst. November to March brings in 77% of the year's output in King County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 3.81 m/s | 480 kWh | $69 |
| February | 3.34 m/s | 284 kWh | $41 |
| March | 3.16 m/s | 264 kWh | $38 |
| April | 2.63 m/s | 135 kWh | $19 |
| May | 2.20 m/s | 69 kWh | $10 |
| June | 2.06 m/s | 50 kWh | $7 |
| July | 1.76 m/s | 23 kWh | $3 |
| August | 1.79 m/s | 25 kWh | $4 |
| September | 2.20 m/s | 67 kWh | $10 |
| October | 2.82 m/s | 179 kWh | $26 |
| November | 3.54 m/s | 370 kWh | $53 |
| December | 3.70 m/s | 439 kWh | $63 |
What a taller tower would buy
Measured at 10 m the wind in King County averages 1.83 m/s; at 50 m it is 3.32 m/s. That gives a shear exponent of 0.370, typical of rough, sheltered ground: trees or buildings slow the low wind a lot. Going from 20 m to 50 m takes output from 1,089 to 3,648 kWh a year, 235% more, before counting the extra cost of the taller tower. Why tower height decides it explains the shear behind these numbers.
| Hub height | Average wind | Output | Payback |
|---|---|---|---|
| 20 m | 2.37 m/s | 1,089 kWh | over 100 years |
| 30 m | 2.75 m/s | 1,915 kWh | over 100 years |
| 40 m | 3.06 m/s | 2,772 kWh | over 100 years |
| 50 m | 3.32 m/s | 3,648 kWh | over 100 years |
Counties around King County
4 of the 6 closest counties are windier at turbine height; the windiest, Kittitas County, averages 3.56 m/s.
- Pierce County, WA: 2.87 m/s, 2,232 kWh, payback over 100 years (34 mi)
- Snohomish County, WA: 2.49 m/s, 1,330 kWh, payback over 100 years (39 mi)
- Kitsap County, WA: 2.97 m/s, 2,513 kWh, payback over 100 years (39 mi)
- Kittitas County, WA: 3.56 m/s, 4,570 kWh, payback over 100 years (60 mi)
- Island County, WA: 2.56 m/s, 1,477 kWh, payback over 100 years (60 mi)
- Thurston County, WA: 2.81 m/s, 2,073 kWh, payback over 100 years (60 mi)
Sun versus wind in King County
King County gets 3.76 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,098 kWh a year; one kW of the turbine above makes 192. Kilowatt for kilowatt, panels make 5.7 times as much here as the turbine. Panel output assumes an 80% system performance ratio. Wind or solar runs the same comparison for every county.
How this is worked out
Wind is NASA's Power climate record, the 2001-2025 average at 10 m and 50 m for the county's centre, carried to 30 m with this county's own measured wind shear and spread into hours with a Rayleigh distribution. The turbine is a generic 10 kW, 7 m rotor machine with 10% losses. Cost is $10,000 per kW installed with no tax credit, because the federal one ended in 2025. One county-centre number cannot see your hilltop or your tree line, so treat it as the starting point for a site survey, not a substitute. The full method and its weak spots are in how the numbers are made.