Wind Turbine Payback in Shelby County, IA
Wind turbine payback in Shelby 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 Shelby County, IA averages 6.35 m/s (14.2 mph). A 10 kW turbine there would make about 22,299 kWh a year, worth $3,245 at IA's 14.55¢/kWh. Against an installed cost of about $100,000, that is a payback of 31 years, and the turbine is built to last about 20.
What to do in Shelby County
A home turbine is not worth buying for savings in Shelby County unless your spot is far windier than the county average, 8.1 m/s at the hub against 6.35 m/s here. Per kW, solar panels would make about 1,215 kWh a year here against the turbine's 2,230, 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 6.35. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IA
Shelby County is the 402nd 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 Shelby County
April is the strongest month here, at 7.23 m/s and about 2,359 kWh. July is the weakest, 5.09 m/s and 1,115 kWh, so the best month makes 2.1 times the worst. November to March brings in 47% of the year's output in Shelby County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.70 m/s | 2,111 kWh | $307 |
| February | 6.70 m/s | 1,907 kWh | $277 |
| March | 6.91 m/s | 2,243 kWh | $326 |
| April | 7.23 m/s | 2,359 kWh | $343 |
| May | 6.53 m/s | 2,005 kWh | $292 |
| June | 5.85 m/s | 1,527 kWh | $222 |
| July | 5.09 m/s | 1,115 kWh | $162 |
| August | 5.11 m/s | 1,126 kWh | $164 |
| September | 6.12 m/s | 1,696 kWh | $247 |
| October | 6.62 m/s | 2,061 kWh | $300 |
| November | 6.80 m/s | 2,107 kWh | $307 |
| December | 6.57 m/s | 2,033 kWh | $296 |
What a taller tower would buy
Measured at 10 m the wind in Shelby County averages 4.99 m/s; at 50 m it is 7.1 m/s. That gives a shear exponent of 0.219, typical of ordinary open country. Going from 20 m to 50 m takes output from 18,293 to 27,755 kWh a year, 52% 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 | 5.81 m/s | 18,293 kWh | 38 years |
| 30 m | 6.35 m/s | 22,288 kWh | 31 years |
| 40 m | 6.76 m/s | 25,321 kWh | 27 years |
| 50 m | 7.1 m/s | 27,755 kWh | 25 years |
Counties around Shelby County
2 of the 6 closest counties are windier at turbine height; the windiest, Carroll County, averages 6.42 m/s.
- Audubon County, IA: 6.35 m/s, 22,299 kWh, payback 31 years (21 mi)
- Crawford County, IA: 6.39 m/s, 22,595 kWh, payback 30 years (25 mi)
- Pottawattamie County, IA: 6.31 m/s, 22,003 kWh, payback 31 years (26 mi)
- Harrison County, IA: 6.31 m/s, 22,003 kWh, payback 31 years (27 mi)
- Cass County, IA: 6.35 m/s, 22,299 kWh, payback 31 years (31 mi)
- Carroll County, IA: 6.42 m/s, 22,817 kWh, payback 30 years (34 mi)
Sun versus wind in Shelby County
Shelby County gets 4.16 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,215 kWh a year; one kW of the turbine above makes 2,230. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.8 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.