Wind Turbine Payback in Marshall County, SD
Wind turbine payback in Marshall 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 Marshall County, SD averages 6.68 m/s (14.9 mph). A 10 kW turbine there would make about 24,728 kWh a year, worth $3,605 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 Marshall County
A home turbine is not worth buying for savings in Marshall County unless your spot is far windier than the county average, 8.1 m/s at the hub against 6.68 m/s here. Per kW, solar panels would make about 1,162 kWh a year here against the turbine's 2,473, 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 6.68. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of SD
Marshall County is the 70th 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 Marshall County
October is the strongest month here, at 7.17 m/s and about 2,400 kWh. July is the weakest, 5.75 m/s and 1,514 kWh, so the best month makes 1.6 times the worst. November to March brings in 43% of the year's output in Marshall County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.78 m/s | 2,164 kWh | $316 |
| February | 6.71 m/s | 1,914 kWh | $279 |
| March | 6.89 m/s | 2,230 kWh | $325 |
| April | 7.20 m/s | 2,338 kWh | $341 |
| May | 7.00 m/s | 2,296 kWh | $335 |
| June | 6.33 m/s | 1,822 kWh | $266 |
| July | 5.75 m/s | 1,514 kWh | $221 |
| August | 5.84 m/s | 1,570 kWh | $229 |
| September | 6.88 m/s | 2,153 kWh | $314 |
| October | 7.17 m/s | 2,400 kWh | $350 |
| November | 6.98 m/s | 2,212 kWh | $323 |
| December | 6.74 m/s | 2,136 kWh | $311 |
What a taller tower would buy
Measured at 10 m the wind in Marshall County averages 5.35 m/s; at 50 m it is 7.41 m/s. That gives a shear exponent of 0.202, typical of ordinary open country. Going from 20 m to 50 m takes output from 20,875 to 29,920 kWh a year, 43% 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 | 6.16 m/s | 20,875 kWh | 33 years |
| 30 m | 6.68 m/s | 24,754 kWh | 28 years |
| 40 m | 7.08 m/s | 27,637 kWh | 25 years |
| 50 m | 7.41 m/s | 29,920 kWh | 23 years |
Counties around Marshall County
None of the 6 closest counties is windier than Marshall County.
- Sargent County, ND: 6.44 m/s, 22,964 kWh, payback 35 years (26 mi)
- Day County, SD: 6.68 m/s, 24,728 kWh, payback 28 years (26 mi)
- Roberts County, SD: 6.62 m/s, 24,289 kWh, payback 28 years (32 mi)
- Brown County, SD: 6.3 m/s, 21,929 kWh, payback 31 years (39 mi)
- Richland County, ND: 6.27 m/s, 21,706 kWh, payback 37 years (48 mi)
- Ransom County, ND: 6.28 m/s, 21,781 kWh, payback 37 years (49 mi)
Sun versus wind in Marshall County
Marshall 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 2,473. 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.