Wind Turbine Payback in Franklin County, IA
Wind turbine payback in Franklin 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 Franklin County, IA averages 6.32 m/s (14.1 mph). A 10 kW turbine there would make about 22,077 kWh a year, worth $3,212 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 Franklin County
A home turbine is not worth buying for savings in Franklin County unless your spot is far windier than the county average, 8.1 m/s at the hub against 6.32 m/s here. Per kW, solar panels would make about 1,177 kWh a year here against the turbine's 2,208, so get a solar quote first.
What would have to change
- Power would have to cost 23¢/kWh, 1.6 times what IA pays now.
- Or the average wind at the hub would have to be 8.1 m/s instead of 6.32. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IA
Franklin County is the 452nd 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 Franklin County
April is the strongest month here, at 7.28 m/s and about 2,384 kWh. August is the weakest, 4.98 m/s and 1,053 kWh, so the best month makes 2.3 times the worst. November to March brings in 47% of the year's output in Franklin County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.77 m/s | 2,155 kWh | $314 |
| February | 6.75 m/s | 1,937 kWh | $282 |
| March | 6.89 m/s | 2,232 kWh | $325 |
| April | 7.28 m/s | 2,384 kWh | $347 |
| May | 6.58 m/s | 2,039 kWh | $297 |
| June | 5.76 m/s | 1,473 kWh | $214 |
| July | 5.00 m/s | 1,064 kWh | $155 |
| August | 4.98 m/s | 1,053 kWh | $153 |
| September | 6.01 m/s | 1,625 kWh | $236 |
| October | 6.59 m/s | 2,044 kWh | $297 |
| November | 6.78 m/s | 2,091 kWh | $304 |
| December | 6.59 m/s | 2,044 kWh | $297 |
What a taller tower would buy
Measured at 10 m the wind in Franklin County averages 4.97 m/s; at 50 m it is 7.07 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 18,113 to 27,542 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 | 5.78 m/s | 18,113 kWh | 38 years |
| 30 m | 6.32 m/s | 22,090 kWh | 31 years |
| 40 m | 6.73 m/s | 25,114 kWh | 27 years |
| 50 m | 7.07 m/s | 27,542 kWh | 25 years |
Counties around Franklin County
3 of the 6 closest counties are windier at turbine height; the windiest, Wright County, averages 6.4 m/s.
- Cerro Gordo County, IA: 6.33 m/s, 22,151 kWh, payback 31 years (23 mi)
- Wright County, IA: 6.4 m/s, 22,669 kWh, payback 30 years (24 mi)
- Hardin County, IA: 6.32 m/s, 22,077 kWh, payback 31 years (24 mi)
- Butler County, IA: 6.17 m/s, 20,965 kWh, payback 33 years (25 mi)
- Hamilton County, IA: 6.4 m/s, 22,669 kWh, payback 30 years (33 mi)
- Floyd County, IA: 6.21 m/s, 21,262 kWh, payback 32 years (33 mi)
Sun versus wind in Franklin County
Franklin County gets 4.03 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,177 kWh a year; one kW of the turbine above makes 2,208. 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.