Wind Turbine Payback in Brown County, SD
Wind turbine payback in Brown 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 Brown County, SD averages 6.3 m/s (14.1 mph). A 10 kW turbine there would make about 21,929 kWh a year, worth $3,197 at SD's 14.58¢/kWh. Against an installed cost of about $100,000, that is a payback of 31 years, and the turbine is built to last about 20.
What to do in Brown County
A home turbine is not worth buying for savings in Brown County unless your spot is far windier than the county average, 8.1 m/s at the hub against 6.3 m/s here. Per kW, solar panels would make about 1,197 kWh a year here against the turbine's 2,193, so get a solar quote first.
What would have to change
- Power would have to cost 23¢/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 6.3. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of SD
Brown County is the 474th 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 Brown County
April is the strongest month here, at 6.92 m/s and about 2,176 kWh. July is the weakest, 5.58 m/s and 1,414 kWh, so the best month makes 1.5 times the worst. November to March brings in 41% of the year's output in Brown County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.12 m/s | 1,751 kWh | $255 |
| February | 6.15 m/s | 1,597 kWh | $233 |
| March | 6.53 m/s | 2,004 kWh | $292 |
| April | 6.92 m/s | 2,176 kWh | $317 |
| May | 6.72 m/s | 2,127 kWh | $310 |
| June | 6.07 m/s | 1,662 kWh | $242 |
| July | 5.58 m/s | 1,414 kWh | $206 |
| August | 5.65 m/s | 1,453 kWh | $212 |
| September | 6.57 m/s | 1,967 kWh | $287 |
| October | 6.78 m/s | 2,160 kWh | $315 |
| November | 6.42 m/s | 1,874 kWh | $273 |
| December | 6.14 m/s | 1,762 kWh | $257 |
What a taller tower would buy
Measured at 10 m the wind in Brown County averages 4.98 m/s; at 50 m it is 7.03 m/s. That gives a shear exponent of 0.214, typical of ordinary open country. Going from 20 m to 50 m takes output from 18,066 to 27,257 kWh a year, 51% 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 | 5.78 m/s | 18,066 kWh | 38 years |
| 30 m | 6.3 m/s | 21,944 kWh | 31 years |
| 40 m | 6.7 m/s | 24,890 kWh | 28 years |
| 50 m | 7.03 m/s | 27,257 kWh | 25 years |
Counties around Brown County
6 of the 6 closest counties are windier at turbine height; the windiest, Marshall County, averages 6.68 m/s.
- Dickey County, ND: 6.5 m/s, 23,407 kWh, payback 34 years (36 mi)
- Marshall County, SD: 6.68 m/s, 24,728 kWh, payback 28 years (39 mi)
- Day County, SD: 6.68 m/s, 24,728 kWh, payback 28 years (41 mi)
- Edmunds County, SD: 6.46 m/s, 23,112 kWh, payback 30 years (43 mi)
- McPherson County, SD: 6.65 m/s, 24,509 kWh, payback 28 years (44 mi)
- Spink County, SD: 6.32 m/s, 22,077 kWh, payback 31 years (46 mi)
Sun versus wind in Brown County
Brown County gets 4.1 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,197 kWh a year; one kW of the turbine above makes 2,193. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.8 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.