Wind Turbine Payback in Greene County, IL
Wind turbine payback in Greene 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 Greene County, IL averages 5.67 m/s (12.7 mph). A 10 kW turbine there would make about 17,272 kWh a year, worth $3,321 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 Greene County
A home turbine is not worth buying for savings in Greene County unless your spot is far windier than the county average, 6.8 m/s at the hub against 5.67 m/s here. Per kW, solar panels would make about 1,203 kWh a year here against the turbine's 1,727, so get a solar quote first.
What would have to change
- Power would have to cost 29¢/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 5.67. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IL
Greene County is the 1,142nd 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 Greene County
April is the strongest month here, at 6.58 m/s and about 1,972 kWh. August is the weakest, 4.32 m/s and 704 kWh, so the best month makes 2.8 times the worst. November to March brings in 52% of the year's output in Greene County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.33 m/s | 1,883 kWh | $362 |
| February | 6.28 m/s | 1,671 kWh | $321 |
| March | 6.42 m/s | 1,939 kWh | $373 |
| April | 6.58 m/s | 1,972 kWh | $379 |
| May | 5.64 m/s | 1,445 kWh | $278 |
| June | 4.96 m/s | 1,010 kWh | $194 |
| July | 4.34 m/s | 712 kWh | $137 |
| August | 4.32 m/s | 704 kWh | $135 |
| September | 4.88 m/s | 962 kWh | $185 |
| October | 5.91 m/s | 1,616 kWh | $311 |
| November | 6.29 m/s | 1,796 kWh | $345 |
| December | 6.16 m/s | 1,772 kWh | $341 |
What a taller tower would buy
Measured at 10 m the wind in Greene County averages 4.34 m/s; at 50 m it is 6.42 m/s. That gives a shear exponent of 0.243, typical of ordinary open country. Going from 20 m to 50 m takes output from 13,480 to 22,817 kWh a year, 69% 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 | 5.14 m/s | 13,480 kWh | 39 years |
| 30 m | 5.67 m/s | 17,276 kWh | 30 years |
| 40 m | 6.08 m/s | 20,306 kWh | 26 years |
| 50 m | 6.42 m/s | 22,817 kWh | 23 years |
Counties around Greene County
2 of the 6 closest counties are windier at turbine height; the windiest, Macoupin County, averages 5.84 m/s.
- Jersey County, IL: 5.06 m/s, 12,941 kWh, payback 40 years (19 mi)
- Calhoun County, IL: 5.06 m/s, 12,941 kWh, payback 40 years (20 mi)
- Scott County, IL: 5.67 m/s, 17,272 kWh, payback 30 years (20 mi)
- Macoupin County, IL: 5.84 m/s, 18,521 kWh, payback 28 years (25 mi)
- Morgan County, IL: 5.84 m/s, 18,521 kWh, payback 28 years (27 mi)
- Pike County, IL: 5.67 m/s, 17,272 kWh, payback 30 years (33 mi)
Sun versus wind in Greene County
Greene County gets 4.12 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,203 kWh a year; one kW of the turbine above makes 1,727. 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.