Wind Turbine Payback in Williamson County, IL
Wind turbine payback in Williamson 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 Williamson County, IL averages 4.82 m/s (10.8 mph). A 10 kW turbine there would make about 11,341 kWh a year, worth $2,181 at IL's 19.23¢/kWh. Against an installed cost of about $100,000, that is a payback of 46 years, and the turbine is built to last about 20.
What to do in Williamson County
A home turbine is not worth buying for savings in Williamson County unless your spot is far windier than the county average, 6.8 m/s at the hub against 4.82 m/s here. Per kW, solar panels would make about 1,229 kWh a year here against the turbine's 1,134, so get a solar quote first.
What would have to change
- Power would have to cost 44¢/kWh, 2.3 times what IL pays now.
- Or the average wind at the hub would have to be 6.8 m/s instead of 4.82. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IL
Williamson County is the 1,546th 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 Williamson County
March is the strongest month here, at 5.67 m/s and about 1,464 kWh. July is the weakest, 3.57 m/s and 391 kWh, so the best month makes 3.7 times the worst. November to March brings in 55% of the year's output in Williamson County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 5.53 m/s | 1,379 kWh | $265 |
| February | 5.55 m/s | 1,260 kWh | $242 |
| March | 5.67 m/s | 1,464 kWh | $282 |
| April | 5.73 m/s | 1,458 kWh | $280 |
| May | 4.77 m/s | 936 kWh | $180 |
| June | 4.02 m/s | 550 kWh | $106 |
| July | 3.57 m/s | 391 kWh | $75 |
| August | 3.63 m/s | 412 kWh | $79 |
| September | 4.02 m/s | 550 kWh | $106 |
| October | 4.81 m/s | 955 kWh | $184 |
| November | 5.23 m/s | 1,158 kWh | $223 |
| December | 5.25 m/s | 1,212 kWh | $233 |
What a taller tower would buy
Measured at 10 m the wind in Williamson County averages 3.48 m/s; at 50 m it is 5.6 m/s. That gives a shear exponent of 0.296, typical of ordinary open country. Going from 20 m to 50 m takes output from 8,007 to 16,762 kWh a year, 109% 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 | 4.27 m/s | 8,007 kWh | 65 years |
| 30 m | 4.81 m/s | 11,303 kWh | 46 years |
| 40 m | 5.24 m/s | 14,201 kWh | 37 years |
| 50 m | 5.6 m/s | 16,762 kWh | 31 years |
Counties around Williamson County
3 of the 6 closest counties are windier at turbine height; the windiest, Franklin County, averages 5.51 m/s.
- Franklin County, IL: 5.51 m/s, 16,109 kWh, payback 32 years (18 mi)
- Johnson County, IL: 4.82 m/s, 11,341 kWh, payback 46 years (19 mi)
- Saline County, IL: 5.51 m/s, 16,109 kWh, payback 32 years (21 mi)
- Union County, IL: 4.69 m/s, 10,508 kWh, payback 50 years (24 mi)
- Jackson County, IL: 5.34 m/s, 14,892 kWh, payback 35 years (25 mi)
- Pope County, IL: 4.82 m/s, 11,341 kWh, payback 46 years (30 mi)
Sun versus wind in Williamson County
Williamson County gets 4.21 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,229 kWh a year; one kW of the turbine above makes 1,134. Kilowatt for kilowatt, panels make 1.1 times as much here as the turbine. 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.