Wind Turbine Payback in Clay County, IL
Wind turbine payback in Clay 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 Clay County, IL averages 5.71 m/s (12.8 mph). A 10 kW turbine there would make about 17,565 kWh a year, worth $3,378 at IL's 19.23¢/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 Clay County
A home turbine is not worth buying for savings in Clay County unless your spot is far windier than the county average, 6.8 m/s at the hub against 5.71 m/s here. Per kW, solar panels would make about 1,215 kWh a year here against the turbine's 1,757, so get a solar quote first.
What would have to change
- Power would have to cost 28¢/kWh, 1.5 times what IL pays now.
- Or the average wind at the hub would have to be 6.8 m/s instead of 5.71. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IL
Clay County is the 1,125th windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. The windiest in IL is Cook County at 6.73 m/s, payback 21 years.
Month by month in Clay County
April is the strongest month here, at 6.74 m/s and about 2,069 kWh. July is the weakest, 4.24 m/s and 665 kWh, so the best month makes 3.1 times the worst. November to March brings in 53% of the year's output in Clay County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.48 m/s | 1,973 kWh | $379 |
| February | 6.42 m/s | 1,752 kWh | $337 |
| March | 6.58 m/s | 2,039 kWh | $392 |
| April | 6.74 m/s | 2,069 kWh | $398 |
| May | 5.73 m/s | 1,506 kWh | $290 |
| June | 4.89 m/s | 971 kWh | $187 |
| July | 4.24 m/s | 665 kWh | $128 |
| August | 4.27 m/s | 681 kWh | $131 |
| September | 4.76 m/s | 900 kWh | $173 |
| October | 5.90 m/s | 1,611 kWh | $310 |
| November | 6.37 m/s | 1,845 kWh | $355 |
| December | 6.24 m/s | 1,823 kWh | $351 |
What a taller tower would buy
Measured at 10 m the wind in Clay County averages 4.39 m/s; at 50 m it is 6.46 m/s. That gives a shear exponent of 0.240, typical of ordinary open country. Going from 20 m to 50 m takes output from 13,800 to 23,112 kWh a year, 67% 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 | 5.18 m/s | 13,800 kWh | 38 years |
| 30 m | 5.71 m/s | 17,599 kWh | 30 years |
| 40 m | 6.12 m/s | 20,617 kWh | 25 years |
| 50 m | 6.46 m/s | 23,112 kWh | 23 years |
Counties around Clay County
2 of the 6 closest counties are windier at turbine height; the windiest, Effingham County, averages 5.82 m/s.
- Richland County, IL: 5.61 m/s, 16,834 kWh, payback 31 years (22 mi)
- Effingham County, IL: 5.82 m/s, 18,374 kWh, payback 28 years (22 mi)
- Wayne County, IL: 5.61 m/s, 16,834 kWh, payback 31 years (22 mi)
- Marion County, IL: 5.71 m/s, 17,565 kWh, payback 30 years (25 mi)
- Jasper County, IL: 5.73 m/s, 17,712 kWh, payback 29 years (25 mi)
- Edwards County, IL: 5.61 m/s, 16,834 kWh, payback 31 years (33 mi)
Sun versus wind in Clay County
Clay 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 1,757. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.4 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.