Wind Turbine Payback in San Juan County, WA
Wind turbine payback in San Juan 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 San Juan County, WA averages 3.83 m/s (8.6 mph). A 10 kW turbine there would make about 5,753 kWh a year, worth $830 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 San Juan County
A home turbine is not worth buying for savings in San Juan County unless your spot is far windier than the county average, 8.1 m/s at the hub against 3.83 m/s here. Per kW, solar panels would make about 1,016 kWh a year here against the turbine's 575, so get a solar quote first.
What would have to change
- Power would have to cost 87¢/kWh, 6.0 times what WA pays now.
- Or the average wind at the hub would have to be 8.1 m/s instead of 3.83. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of WA
San Juan County is the 2,190th 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 San Juan County
December is the strongest month here, at 4.82 m/s and about 965 kWh. September is the weakest, 3.03 m/s and 222 kWh, so the best month makes 4.3 times the worst. November to March brings in 63% of the year's output in San Juan County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 4.67 m/s | 881 kWh | $127 |
| February | 4.22 m/s | 591 kWh | $85 |
| March | 4.14 m/s | 621 kWh | $90 |
| April | 3.62 m/s | 398 kWh | $57 |
| May | 3.26 m/s | 292 kWh | $42 |
| June | 3.45 m/s | 340 kWh | $49 |
| July | 3.42 m/s | 343 kWh | $49 |
| August | 3.16 m/s | 264 kWh | $38 |
| September | 3.03 m/s | 222 kWh | $32 |
| October | 3.69 m/s | 434 kWh | $63 |
| November | 4.59 m/s | 811 kWh | $117 |
| December | 4.82 m/s | 965 kWh | $139 |
What a taller tower would buy
Measured at 10 m the wind in San Juan County averages 3.12 m/s; at 50 m it is 4.22 m/s. That gives a shear exponent of 0.188, typical of ordinary open country. Going from 20 m to 50 m takes output from 4,539 to 7,732 kWh a year, 70% 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 | 3.55 m/s | 4,539 kWh | over 100 years |
| 30 m | 3.83 m/s | 5,770 kWh | over 100 years |
| 40 m | 4.05 m/s | 6,814 kWh | over 100 years |
| 50 m | 4.22 m/s | 7,732 kWh | 90 years |
Counties around San Juan County
None of the 6 closest counties is windier than San Juan County.
- Island County, WA: 2.56 m/s, 1,477 kWh, payback over 100 years (31 mi)
- Clallam County, WA: 3.01 m/s, 2,631 kWh, payback over 100 years (45 mi)
- Jefferson County, WA: 3.01 m/s, 2,631 kWh, payback over 100 years (52 mi)
- Skagit County, WA: 2.34 m/s, 1,043 kWh, payback over 100 years (59 mi)
- Whatcom County, WA: 2.31 m/s, 989 kWh, payback over 100 years (62 mi)
- Kitsap County, WA: 2.97 m/s, 2,513 kWh, payback over 100 years (64 mi)
Sun versus wind in San Juan County
San Juan County gets 3.48 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,016 kWh a year; one kW of the turbine above makes 575. Kilowatt for kilowatt, panels make 1.8 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.