Wind Turbine Payback in Carroll County, IA
Wind turbine payback in Carroll 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 Carroll County, IA averages 6.42 m/s (14.4 mph). A 10 kW turbine there would make about 22,817 kWh a year, worth $3,320 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 Carroll County
A home turbine is not worth buying for savings in Carroll County unless your spot is far windier than the county average, 8.1 m/s at the hub against 6.42 m/s here. Per kW, solar panels would make about 1,186 kWh a year here against the turbine's 2,282, so get a solar quote first.
What would have to change
- Power would have to cost 22¢/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 6.42. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IA
Carroll County is the 301st 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 Carroll County
April is the strongest month here, at 7.27 m/s and about 2,378 kWh. July is the weakest, 5.17 m/s and 1,165 kWh, so the best month makes 2.0 times the worst. November to March brings in 47% of the year's output in Carroll County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.78 m/s | 2,165 kWh | $315 |
| February | 6.77 m/s | 1,945 kWh | $283 |
| March | 6.92 m/s | 2,247 kWh | $327 |
| April | 7.27 m/s | 2,378 kWh | $346 |
| May | 6.61 m/s | 2,060 kWh | $300 |
| June | 5.92 m/s | 1,569 kWh | $228 |
| July | 5.17 m/s | 1,165 kWh | $170 |
| August | 5.18 m/s | 1,171 kWh | $170 |
| September | 6.19 m/s | 1,738 kWh | $253 |
| October | 6.69 m/s | 2,104 kWh | $306 |
| November | 6.87 m/s | 2,143 kWh | $312 |
| December | 6.67 m/s | 2,093 kWh | $305 |
What a taller tower would buy
Measured at 10 m the wind in Carroll County averages 5.06 m/s; at 50 m it is 7.17 m/s. That gives a shear exponent of 0.217, typical of ordinary open country. Going from 20 m to 50 m takes output from 18,795 to 28,250 kWh a year, 50% 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 | 5.88 m/s | 18,795 kWh | 37 years |
| 30 m | 6.42 m/s | 22,800 kWh | 30 years |
| 40 m | 6.83 m/s | 25,827 kWh | 27 years |
| 50 m | 7.17 m/s | 28,250 kWh | 24 years |
Counties around Carroll County
1 of the 6 closest counties is windier at turbine height; the windiest, Sac County, averages 6.45 m/s.
- Greene County, IA: 6.31 m/s, 22,003 kWh, payback 31 years (25 mi)
- Audubon County, IA: 6.35 m/s, 22,299 kWh, payback 31 years (25 mi)
- Calhoun County, IA: 6.4 m/s, 22,669 kWh, payback 30 years (27 mi)
- Crawford County, IA: 6.39 m/s, 22,595 kWh, payback 30 years (27 mi)
- Sac County, IA: 6.45 m/s, 23,038 kWh, payback 30 years (27 mi)
- Guthrie County, IA: 6.29 m/s, 21,855 kWh, payback 31 years (31 mi)
Sun versus wind in Carroll County
Carroll County gets 4.06 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,186 kWh a year; one kW of the turbine above makes 2,282. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.9 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.