Wind Turbine Payback in Clay County, IA
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, IA averages 6.48 m/s (14.5 mph). A 10 kW turbine there would make about 23,260 kWh a year, worth $3,384 at IA's 14.55¢/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 6.48 m/s here. Per kW, solar panels would make about 1,188 kWh a year here against the turbine's 2,326, so get a solar quote first.
What would have to change
- Power would have to cost 21¢/kWh, 1.5 times what IA pays now.
- Or the average wind at the hub would have to be 8.1 m/s instead of 6.48. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IA
Clay County is the 228th windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. The windiest in IA is Dickinson County at 6.59 m/s, payback 29 years.
Month by month in Clay County
April is the strongest month here, at 7.36 m/s and about 2,432 kWh. August is the weakest, 5.28 m/s and 1,228 kWh, so the best month makes 2.0 times the worst. November to March brings in 46% of the year's output in Clay County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.76 m/s | 2,150 kWh | $313 |
| February | 6.78 m/s | 1,952 kWh | $284 |
| March | 6.96 m/s | 2,271 kWh | $330 |
| April | 7.36 m/s | 2,432 kWh | $354 |
| May | 6.74 m/s | 2,139 kWh | $311 |
| June | 6.04 m/s | 1,645 kWh | $239 |
| July | 5.32 m/s | 1,250 kWh | $182 |
| August | 5.28 m/s | 1,228 kWh | $179 |
| September | 6.33 m/s | 1,820 kWh | $265 |
| October | 6.79 m/s | 2,167 kWh | $315 |
| November | 6.85 m/s | 2,134 kWh | $310 |
| December | 6.67 m/s | 2,094 kWh | $305 |
What a taller tower would buy
Measured at 10 m the wind in Clay County averages 5.14 m/s; at 50 m it is 7.22 m/s. That gives a shear exponent of 0.211, typical of ordinary open country. Going from 20 m to 50 m takes output from 19,339 to 28,601 kWh a year, 48% 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 | 5.95 m/s | 19,339 kWh | 36 years |
| 30 m | 6.48 m/s | 23,276 kWh | 30 years |
| 40 m | 6.89 m/s | 26,238 kWh | 26 years |
| 50 m | 7.22 m/s | 28,601 kWh | 24 years |
Counties around Clay County
3 of the 6 closest counties are windier at turbine height; the windiest, Dickinson County, averages 6.59 m/s.
- Dickinson County, IA: 6.59 m/s, 24,069 kWh, payback 29 years (21 mi)
- Buena Vista County, IA: 6.45 m/s, 23,038 kWh, payback 30 years (23 mi)
- O'Brien County, IA: 6.48 m/s, 23,260 kWh, payback 30 years (24 mi)
- Palo Alto County, IA: 6.46 m/s, 23,112 kWh, payback 30 years (24 mi)
- Emmet County, IA: 6.5 m/s, 23,407 kWh, payback 29 years (32 mi)
- Osceola County, IA: 6.57 m/s, 23,922 kWh, payback 29 years (32 mi)
Sun versus wind in Clay County
Clay County gets 4.07 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,188 kWh a year; one kW of the turbine above makes 2,326. 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.