Wind Turbine Payback in Clay County, SD
Wind turbine payback in Clay 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 Clay 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 Clay County
A home turbine is not worth buying for savings in Clay 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 1,215 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
Clay 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 Clay County
April is the strongest month here, at 7.20 m/s and about 2,341 kWh. August is the weakest, 5.41 m/s and 1,308 kWh, so the best month makes 1.8 times the worst. November to March brings in 44% of the year's output in Clay County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.50 m/s | 1,985 kWh | $289 |
| February | 6.50 m/s | 1,798 kWh | $262 |
| March | 6.85 m/s | 2,202 kWh | $321 |
| April | 7.20 m/s | 2,341 kWh | $341 |
| May | 6.68 m/s | 2,103 kWh | $307 |
| June | 6.07 m/s | 1,665 kWh | $243 |
| July | 5.41 m/s | 1,308 kWh | $191 |
| August | 5.41 m/s | 1,308 kWh | $191 |
| September | 6.45 m/s | 1,894 kWh | $276 |
| October | 6.73 m/s | 2,130 kWh | $311 |
| November | 6.60 m/s | 1,986 kWh | $290 |
| December | 6.37 m/s | 1,907 kWh | $278 |
What a taller tower would buy
Measured at 10 m the wind in Clay County averages 5.05 m/s; at 50 m it is 7.14 m/s. That gives a shear exponent of 0.215, typical of ordinary open country. Going from 20 m to 50 m takes output from 18,693 to 28,038 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 | 5.86 m/s | 18,693 kWh | 37 years |
| 30 m | 6.4 m/s | 22,649 kWh | 30 years |
| 40 m | 6.81 m/s | 25,642 kWh | 27 years |
| 50 m | 7.14 m/s | 28,038 kWh | 25 years |
Counties around Clay County
5 of the 6 closest counties are windier at turbine height; the windiest, Cedar County, averages 6.66 m/s.
- Union County, SD: 6.4 m/s, 22,669 kWh, payback 30 years (18 mi)
- Yankton County, SD: 6.47 m/s, 23,186 kWh, payback 30 years (22 mi)
- Cedar County, NE: 6.66 m/s, 24,582 kWh, payback 32 years (26 mi)
- Lincoln County, SD: 6.46 m/s, 23,112 kWh, payback 30 years (28 mi)
- Turner County, SD: 6.46 m/s, 23,112 kWh, payback 30 years (28 mi)
- Dixon County, NE: 6.52 m/s, 23,554 kWh, payback 33 years (30 mi)
Sun versus wind in Clay County
Clay County gets 4.16 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,215 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.