Wind Turbine Payback in Butte County, SD
Wind turbine payback in Butte 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 Butte County, SD averages 6.15 m/s (13.8 mph). A 10 kW turbine there would make about 20,816 kWh a year, worth $3,035 at SD's 14.58¢/kWh. Against an installed cost of about $100,000, that is a payback of 33 years, and the turbine is built to last about 20.
What to do in Butte County
A home turbine is not worth buying for savings in Butte County unless your spot is far windier than the county average, 8.1 m/s at the hub against 6.15 m/s here. Per kW, solar panels would make about 1,241 kWh a year here against the turbine's 2,082, so get a solar quote first.
What would have to change
- Power would have to cost 24¢/kWh, 1.6 times what SD pays now.
- Or the average wind at the hub would have to be 8.1 m/s instead of 6.15. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of SD
Butte County is the 638th 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 Butte County
January is the strongest month here, at 7.03 m/s and about 2,316 kWh. July is the weakest, 5.11 m/s and 1,127 kWh, so the best month makes 2.1 times the worst. November to March brings in 49% of the year's output in Butte County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 7.03 m/s | 2,316 kWh | $338 |
| February | 6.37 m/s | 1,722 kWh | $251 |
| March | 6.35 m/s | 1,895 kWh | $276 |
| April | 6.24 m/s | 1,769 kWh | $258 |
| May | 6.07 m/s | 1,720 kWh | $251 |
| June | 5.61 m/s | 1,383 kWh | $202 |
| July | 5.11 m/s | 1,127 kWh | $164 |
| August | 5.26 m/s | 1,217 kWh | $177 |
| September | 5.77 m/s | 1,480 kWh | $216 |
| October | 6.53 m/s | 2,007 kWh | $293 |
| November | 6.61 m/s | 1,991 kWh | $290 |
| December | 6.83 m/s | 2,190 kWh | $319 |
What a taller tower would buy
Measured at 10 m the wind in Butte County averages 4.84 m/s; at 50 m it is 6.87 m/s. That gives a shear exponent of 0.218, typical of ordinary open country. Going from 20 m to 50 m takes output from 16,952 to 26,109 kWh a year, 54% 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 | 5.63 m/s | 16,952 kWh | 41 years |
| 30 m | 6.15 m/s | 20,787 kWh | 33 years |
| 40 m | 6.54 m/s | 23,730 kWh | 29 years |
| 50 m | 6.87 m/s | 26,109 kWh | 26 years |
Counties around Butte County
4 of the 6 closest counties are windier at turbine height; the windiest, Harding County, averages 6.62 m/s.
- Lawrence County, SD: 5.27 m/s, 14,397 kWh, payback 48 years (41 mi)
- Meade County, SD: 6.32 m/s, 22,077 kWh, payback 31 years (44 mi)
- Harding County, SD: 6.62 m/s, 24,289 kWh, payback 28 years (48 mi)
- Crook County, WY: 5.61 m/s, 16,834 kWh, payback 42 years (56 mi)
- Perkins County, SD: 6.58 m/s, 23,996 kWh, payback 29 years (65 mi)
- Carter County, MT: 6.54 m/s, 23,702 kWh, payback 30 years (65 mi)
Sun versus wind in Butte County
Butte County gets 4.25 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,241 kWh a year; one kW of the turbine above makes 2,082. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.7 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.