Wind Turbine Payback in Roberts County, SD
Wind turbine payback in Roberts 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 Roberts County, SD averages 6.62 m/s (14.8 mph). A 10 kW turbine there would make about 24,289 kWh a year, worth $3,541 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 Roberts County
A home turbine is not worth buying for savings in Roberts County unless your spot is far windier than the county average, 8.1 m/s at the hub against 6.62 m/s here. Per kW, solar panels would make about 1,162 kWh a year here against the turbine's 2,429, so get a solar quote first.
What would have to change
- Power would have to cost 21¢/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 6.62. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of SD
Roberts County is the 102nd 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 Roberts County
October is the strongest month here, at 7.12 m/s and about 2,369 kWh. July is the weakest, 5.61 m/s and 1,428 kWh, so the best month makes 1.7 times the worst. November to March brings in 44% of the year's output in Roberts County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.91 m/s | 2,244 kWh | $327 |
| February | 6.80 m/s | 1,967 kWh | $287 |
| March | 6.79 m/s | 2,166 kWh | $316 |
| April | 7.06 m/s | 2,256 kWh | $329 |
| May | 6.86 m/s | 2,211 kWh | $322 |
| June | 6.22 m/s | 1,754 kWh | $256 |
| July | 5.61 m/s | 1,428 kWh | $208 |
| August | 5.68 m/s | 1,473 kWh | $215 |
| September | 6.71 m/s | 2,053 kWh | $299 |
| October | 7.12 m/s | 2,369 kWh | $345 |
| November | 6.98 m/s | 2,214 kWh | $323 |
| December | 6.77 m/s | 2,155 kWh | $314 |
What a taller tower would buy
Measured at 10 m the wind in Roberts County averages 5.28 m/s; at 50 m it is 7.36 m/s. That gives a shear exponent of 0.206, typical of ordinary open country. Going from 20 m to 50 m takes output from 20,401 to 29,576 kWh a year, 45% 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 | 6.09 m/s | 20,401 kWh | 34 years |
| 30 m | 6.62 m/s | 24,325 kWh | 28 years |
| 40 m | 7.03 m/s | 27,252 kWh | 25 years |
| 50 m | 7.36 m/s | 29,576 kWh | 23 years |
Counties around Roberts County
3 of the 6 closest counties are windier at turbine height; the windiest, Grant County, averages 6.71 m/s.
- Traverse County, MN: 6.37 m/s, 22,447 kWh, payback 27 years (25 mi)
- Big Stone County, MN: 6.34 m/s, 22,225 kWh, payback 27 years (30 mi)
- Marshall County, SD: 6.68 m/s, 24,728 kWh, payback 28 years (32 mi)
- Grant County, SD: 6.71 m/s, 24,947 kWh, payback 28 years (32 mi)
- Day County, SD: 6.68 m/s, 24,728 kWh, payback 28 years (36 mi)
- Richland County, ND: 6.27 m/s, 21,706 kWh, payback 37 years (44 mi)
Sun versus wind in Roberts County
Roberts County gets 3.98 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,162 kWh a year; one kW of the turbine above makes 2,429. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 2.1 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.