Wind Turbine Payback in Clark County, SD
Wind turbine payback in Clark 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 Clark County, SD averages 6.66 m/s (14.9 mph). A 10 kW turbine there would make about 24,582 kWh a year, worth $3,584 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 Clark County
A home turbine is not worth buying for savings in Clark County unless your spot is far windier than the county average, 8.1 m/s at the hub against 6.66 m/s here. Per kW, solar panels would make about 1,191 kWh a year here against the turbine's 2,458, 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 6.66. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of SD
Clark County is the 84th 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 Clark County
April is the strongest month here, at 7.29 m/s and about 2,391 kWh. July is the weakest, 5.76 m/s and 1,522 kWh, so the best month makes 1.6 times the worst. November to March brings in 43% of the year's output in Clark County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.65 m/s | 2,081 kWh | $303 |
| February | 6.66 m/s | 1,885 kWh | $275 |
| March | 6.94 m/s | 2,259 kWh | $329 |
| April | 7.29 m/s | 2,391 kWh | $349 |
| May | 6.99 m/s | 2,292 kWh | $334 |
| June | 6.33 m/s | 1,823 kWh | $266 |
| July | 5.76 m/s | 1,522 kWh | $222 |
| August | 5.80 m/s | 1,550 kWh | $226 |
| September | 6.87 m/s | 2,149 kWh | $313 |
| October | 7.12 m/s | 2,368 kWh | $345 |
| November | 6.88 m/s | 2,154 kWh | $314 |
| December | 6.63 m/s | 2,070 kWh | $302 |
What a taller tower would buy
Measured at 10 m the wind in Clark County averages 5.32 m/s; at 50 m it is 7.39 m/s. That gives a shear exponent of 0.204, typical of ordinary open country. Going from 20 m to 50 m takes output from 20,669 to 29,783 kWh a year, 44% 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 | 6.13 m/s | 20,669 kWh | 33 years |
| 30 m | 6.66 m/s | 24,572 kWh | 28 years |
| 40 m | 7.06 m/s | 27,479 kWh | 25 years |
| 50 m | 7.39 m/s | 29,783 kWh | 23 years |
Counties around Clark County
2 of the 6 closest counties are windier at turbine height; the windiest, Hamlin County, averages 6.69 m/s.
- Codington County, SD: 6.66 m/s, 24,582 kWh, payback 28 years (27 mi)
- Hamlin County, SD: 6.69 m/s, 24,801 kWh, payback 28 years (29 mi)
- Spink County, SD: 6.32 m/s, 22,077 kWh, payback 31 years (30 mi)
- Day County, SD: 6.68 m/s, 24,728 kWh, payback 28 years (35 mi)
- Kingsbury County, SD: 6.57 m/s, 23,922 kWh, payback 29 years (36 mi)
- Beadle County, SD: 6.34 m/s, 22,225 kWh, payback 31 years (41 mi)
Sun versus wind in Clark County
Clark County gets 4.08 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,191 kWh a year; one kW of the turbine above makes 2,458. 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.