Wind Turbine Payback in Douglas County, SD
Wind turbine payback in Douglas 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 Douglas County, SD averages 6.4 m/s (14.3 mph). A 10 kW turbine there would make about 22,669 kWh a year, worth $3,305 at SD's 14.58¢/kWh. Against an installed cost of about $100,000, that is a payback of 30 years, and the turbine is built to last about 20.
What to do in Douglas County
A home turbine is not worth buying for savings in Douglas County unless your spot is far windier than the county average, 8.1 m/s at the hub against 6.4 m/s here. Per kW, solar panels would make about 1,221 kWh a year here against the turbine's 2,267, so get a solar quote first.
What would have to change
- Power would have to cost 22¢/kWh, 1.5 times what SD pays now.
- Or the average wind at the hub would have to be 8.1 m/s instead of 6.4. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of SD
Douglas County is the 322nd windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. The windiest in SD is Todd County at 6.77 m/s, payback 27 years.
Month by month in Douglas County
April is the strongest month here, at 7.05 m/s and about 2,251 kWh. July is the weakest, 5.53 m/s and 1,383 kWh, so the best month makes 1.6 times the worst. November to March brings in 43% of the year's output in Douglas County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.52 m/s | 2,000 kWh | $292 |
| February | 6.46 m/s | 1,771 kWh | $258 |
| March | 6.76 m/s | 2,151 kWh | $314 |
| April | 7.05 m/s | 2,251 kWh | $328 |
| May | 6.65 m/s | 2,084 kWh | $304 |
| June | 6.05 m/s | 1,652 kWh | $241 |
| July | 5.53 m/s | 1,383 kWh | $202 |
| August | 5.60 m/s | 1,422 kWh | $207 |
| September | 6.55 m/s | 1,952 kWh | $285 |
| October | 6.77 m/s | 2,156 kWh | $314 |
| November | 6.60 m/s | 1,984 kWh | $289 |
| December | 6.38 m/s | 1,910 kWh | $278 |
What a taller tower would buy
Measured at 10 m the wind in Douglas County averages 5.05 m/s; at 50 m it is 7.15 m/s. That gives a shear exponent of 0.216, typical of ordinary open country. Going from 20 m to 50 m takes output from 18,714 to 28,109 kWh a year, 50% 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 | 5.87 m/s | 18,714 kWh | 37 years |
| 30 m | 6.4 m/s | 22,691 kWh | 30 years |
| 40 m | 6.81 m/s | 25,700 kWh | 27 years |
| 50 m | 7.15 m/s | 28,109 kWh | 24 years |
Counties around Douglas County
5 of the 6 closest counties are windier at turbine height; the windiest, Charles Mix County, averages 6.52 m/s.
- Charles Mix County, SD: 6.52 m/s, 23,554 kWh, payback 29 years (17 mi)
- Davison County, SD: 6.4 m/s, 22,669 kWh, payback 30 years (22 mi)
- Aurora County, SD: 6.41 m/s, 22,743 kWh, payback 30 years (26 mi)
- Hutchinson County, SD: 6.45 m/s, 23,038 kWh, payback 30 years (31 mi)
- Hanson County, SD: 6.45 m/s, 23,038 kWh, payback 30 years (35 mi)
- Bon Homme County, SD: 6.45 m/s, 23,038 kWh, payback 30 years (37 mi)
Sun versus wind in Douglas County
Douglas County gets 4.18 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,221 kWh a year; one kW of the turbine above makes 2,267. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.9 times. 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.