Wind Turbine Payback in Gregory County, SD
Wind turbine payback in Gregory 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 Gregory County, SD averages 6.65 m/s (14.9 mph). A 10 kW turbine there would make about 24,509 kWh a year, worth $3,573 at SD's 14.58¢/kWh. Against an installed cost of about $100,000, that is a payback of 28 years, and the turbine is built to last about 20.
What to do in Gregory County
A home turbine is not worth buying for savings in Gregory County unless your spot is far windier than the county average, 8.1 m/s at the hub against 6.65 m/s here. Per kW, solar panels would make about 1,235 kWh a year here against the turbine's 2,451, so get a solar quote first.
What would have to change
- Power would have to cost 20¢/kWh, 1.4 times what SD pays now.
- Or the average wind at the hub would have to be 8.1 m/s instead of 6.65. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of SD
Gregory County is the 92nd 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 Gregory County
January is the strongest month here, at 7.13 m/s and about 2,372 kWh. July is the weakest, 5.67 m/s and 1,468 kWh, so the best month makes 1.6 times the worst. November to March brings in 45% of the year's output in Gregory County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 7.13 m/s | 2,372 kWh | $346 |
| February | 6.81 m/s | 1,970 kWh | $287 |
| March | 6.93 m/s | 2,253 kWh | $328 |
| April | 7.13 m/s | 2,296 kWh | $335 |
| May | 6.74 m/s | 2,137 kWh | $312 |
| June | 6.09 m/s | 1,676 kWh | $244 |
| July | 5.67 m/s | 1,468 kWh | $214 |
| August | 5.73 m/s | 1,507 kWh | $220 |
| September | 6.65 m/s | 2,014 kWh | $294 |
| October | 6.97 m/s | 2,280 kWh | $332 |
| November | 7.02 m/s | 2,233 kWh | $326 |
| December | 6.97 m/s | 2,280 kWh | $332 |
What a taller tower would buy
Measured at 10 m the wind in Gregory County averages 5.27 m/s; at 50 m it is 7.41 m/s. That gives a shear exponent of 0.212, typical of ordinary open country. Going from 20 m to 50 m takes output from 20,459 to 29,920 kWh a year, 46% 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 | 6.1 m/s | 20,459 kWh | 34 years |
| 30 m | 6.65 m/s | 24,505 kWh | 28 years |
| 40 m | 7.07 m/s | 27,525 kWh | 25 years |
| 50 m | 7.41 m/s | 29,920 kWh | 23 years |
Counties around Gregory County
1 of the 6 closest counties is windier at turbine height; the windiest, Keya Paha County, averages 6.73 m/s.
- Boyd County, NE: 6.52 m/s, 23,554 kWh, payback 33 years (29 mi)
- Charles Mix County, SD: 6.52 m/s, 23,554 kWh, payback 29 years (31 mi)
- Keya Paha County, NE: 6.73 m/s, 25,093 kWh, payback 31 years (33 mi)
- Tripp County, SD: 6.49 m/s, 23,333 kWh, payback 29 years (36 mi)
- Brule County, SD: 6.45 m/s, 23,038 kWh, payback 30 years (39 mi)
- Douglas County, SD: 6.4 m/s, 22,669 kWh, payback 30 years (45 mi)
Sun versus wind in Gregory County
Gregory County gets 4.23 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,235 kWh a year; one kW of the turbine above makes 2,451. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 2.0 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.