Wind Turbine Payback in Knox County, IN
Wind turbine payback in Knox 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 Knox County, IN averages 5.53 m/s (12.4 mph). A 10 kW turbine there would make about 16,254 kWh a year, worth $2,770 at IN's 17.04¢/kWh. Against an installed cost of about $100,000, that is a payback of 36 years, and the turbine is built to last about 20.
What to do in Knox County
A home turbine is not worth buying for savings in Knox County unless your spot is far windier than the county average, 7.3 m/s at the hub against 5.53 m/s here. Per kW, solar panels would make about 1,206 kWh a year here against the turbine's 1,625, so get a solar quote first.
What would have to change
- Power would have to cost 31¢/kWh, 1.8 times what IN pays now.
- Or the average wind at the hub would have to be 7.3 m/s instead of 5.53. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IN
Knox County is the 1,195th windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. The windiest in IN is Lake County at 6.17 m/s, payback 28 years.
Month by month in Knox County
April is the strongest month here, at 6.56 m/s and about 1,959 kWh. July is the weakest, 4.05 m/s and 582 kWh, so the best month makes 3.4 times the worst. November to March brings in 53% of the year's output in Knox County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.29 m/s | 1,858 kWh | $317 |
| February | 6.25 m/s | 1,654 kWh | $282 |
| March | 6.40 m/s | 1,925 kWh | $328 |
| April | 6.56 m/s | 1,959 kWh | $334 |
| May | 5.54 m/s | 1,389 kWh | $237 |
| June | 4.72 m/s | 882 kWh | $150 |
| July | 4.05 m/s | 582 kWh | $99 |
| August | 4.06 m/s | 586 kWh | $100 |
| September | 4.61 m/s | 823 kWh | $140 |
| October | 5.69 m/s | 1,477 kWh | $252 |
| November | 6.13 m/s | 1,696 kWh | $289 |
| December | 6.06 m/s | 1,709 kWh | $291 |
What a taller tower would buy
Measured at 10 m the wind in Knox County averages 4.21 m/s; at 50 m it is 6.27 m/s. That gives a shear exponent of 0.247, typical of ordinary open country. Going from 20 m to 50 m takes output from 12,535 to 21,706 kWh a year, 73% 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 m/s | 12,535 kWh | 47 years |
| 30 m | 5.53 m/s | 16,230 kWh | 36 years |
| 40 m | 5.93 m/s | 19,214 kWh | 31 years |
| 50 m | 6.27 m/s | 21,706 kWh | 27 years |
Counties around Knox County
2 of the 6 closest counties are windier at turbine height; the windiest, Sullivan County, averages 5.61 m/s.
- Lawrence County, IL: 5.53 m/s, 16,254 kWh, payback 32 years (17 mi)
- Daviess County, IN: 4.61 m/s, 10,008 kWh, payback 59 years (19 mi)
- Pike County, IN: 5.53 m/s, 16,254 kWh, payback 36 years (22 mi)
- Gibson County, IN: 5.53 m/s, 16,254 kWh, payback 36 years (27 mi)
- Sullivan County, IN: 5.61 m/s, 16,834 kWh, payback 35 years (28 mi)
- Wabash County, IL: 5.61 m/s, 16,834 kWh, payback 31 years (28 mi)
Sun versus wind in Knox County
Knox County gets 4.13 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,206 kWh a year; one kW of the turbine above makes 1,625. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.3 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.