Wind Turbine Payback in Decatur County, IA
Wind turbine payback in Decatur 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 Decatur County, IA averages 6.05 m/s (13.5 mph). A 10 kW turbine there would make about 20,075 kWh a year, worth $2,921 at IA's 14.55¢/kWh. Against an installed cost of about $100,000, that is a payback of 34 years, and the turbine is built to last about 20.
What to do in Decatur County
A home turbine is not worth buying for savings in Decatur County unless your spot is far windier than the county average, 8.1 m/s at the hub against 6.05 m/s here. Per kW, solar panels would make about 1,209 kWh a year here against the turbine's 2,008, so get a solar quote first.
What would have to change
- Power would have to cost 25¢/kWh, 1.7 times what IA pays now.
- Or the average wind at the hub would have to be 8.1 m/s instead of 6.05. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IA
Decatur County is the 769th 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 Decatur County
April is the strongest month here, at 6.92 m/s and about 2,173 kWh. August is the weakest, 4.76 m/s and 930 kWh, so the best month makes 2.3 times the worst. November to March brings in 48% of the year's output in Decatur County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.45 m/s | 1,959 kWh | $285 |
| February | 6.46 m/s | 1,775 kWh | $258 |
| March | 6.76 m/s | 2,147 kWh | $312 |
| April | 6.92 m/s | 2,173 kWh | $316 |
| May | 6.11 m/s | 1,741 kWh | $253 |
| June | 5.52 m/s | 1,331 kWh | $194 |
| July | 4.84 m/s | 973 kWh | $142 |
| August | 4.76 m/s | 930 kWh | $135 |
| September | 5.65 m/s | 1,405 kWh | $204 |
| October | 6.33 m/s | 1,881 kWh | $274 |
| November | 6.54 m/s | 1,950 kWh | $284 |
| December | 6.27 m/s | 1,842 kWh | $268 |
What a taller tower would buy
Measured at 10 m the wind in Decatur County averages 4.68 m/s; at 50 m it is 6.81 m/s. That gives a shear exponent of 0.233, typical of ordinary open country. Going from 20 m to 50 m takes output from 16,043 to 25,675 kWh a year, 60% 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 | 5.5 m/s | 16,043 kWh | 43 years |
| 30 m | 6.05 m/s | 20,044 kWh | 34 years |
| 40 m | 6.46 m/s | 23,149 kWh | 30 years |
| 50 m | 6.81 m/s | 25,675 kWh | 27 years |
Counties around Decatur County
3 of the 6 closest counties are windier at turbine height; the windiest, Clarke County, averages 6.16 m/s.
- Clarke County, IA: 6.16 m/s, 20,891 kWh, payback 33 years (20 mi)
- Wayne County, IA: 5.93 m/s, 19,186 kWh, payback 36 years (24 mi)
- Ringgold County, IA: 6.06 m/s, 20,149 kWh, payback 34 years (24 mi)
- Mercer County, MO: 6.05 m/s, 20,075 kWh, payback 35 years (25 mi)
- Harrison County, MO: 6.05 m/s, 20,075 kWh, payback 35 years (29 mi)
- Lucas County, IA: 6.1 m/s, 20,446 kWh, payback 34 years (31 mi)
Sun versus wind in Decatur County
Decatur County gets 4.14 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,209 kWh a year; one kW of the turbine above makes 2,008. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.7 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.