Wind Turbine Payback in St. Clair County, IL
Wind turbine payback in St. Clair 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 St. Clair County, IL averages 5.05 m/s (11.3 mph). A 10 kW turbine there would make about 12,873 kWh a year, worth $2,476 at IL's 19.23¢/kWh. Against an installed cost of about $100,000, that is a payback of 40 years, and the turbine is built to last about 20.
What to do in St. Clair County
A home turbine is not worth buying for savings in St. Clair County unless your spot is far windier than the county average, 6.8 m/s at the hub against 5.05 m/s here. Per kW, solar panels would make about 1,221 kWh a year here against the turbine's 1,287, so get a solar quote first.
What would have to change
- Power would have to cost 39¢/kWh, 2.0 times what IL pays now.
- Or the average wind at the hub would have to be 6.8 m/s instead of 5.05. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IL
St. Clair County is the 1,430th 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 St. Clair County
April is the strongest month here, at 5.93 m/s and about 1,575 kWh. July is the weakest, 3.77 m/s and 466 kWh, so the best month makes 3.4 times the worst. November to March brings in 54% of the year's output in St. Clair County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 5.74 m/s | 1,513 kWh | $291 |
| February | 5.74 m/s | 1,362 kWh | $262 |
| March | 5.82 m/s | 1,562 kWh | $300 |
| April | 5.93 m/s | 1,575 kWh | $303 |
| May | 5.00 m/s | 1,063 kWh | $204 |
| June | 4.31 m/s | 677 kWh | $130 |
| July | 3.77 m/s | 466 kWh | $90 |
| August | 3.80 m/s | 476 kWh | $92 |
| September | 4.25 m/s | 649 kWh | $125 |
| October | 5.18 m/s | 1,169 kWh | $225 |
| November | 5.59 m/s | 1,370 kWh | $263 |
| December | 5.54 m/s | 1,384 kWh | $266 |
What a taller tower would buy
Measured at 10 m the wind in St. Clair County averages 3.73 m/s; at 50 m it is 5.81 m/s. That gives a shear exponent of 0.275, typical of ordinary open country. Going from 20 m to 50 m takes output from 9,434 to 18,300 kWh a year, 94% 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 | 4.52 m/s | 9,434 kWh | 55 years |
| 30 m | 5.05 m/s | 12,864 kWh | 40 years |
| 40 m | 5.46 m/s | 15,779 kWh | 33 years |
| 50 m | 5.81 m/s | 18,300 kWh | 28 years |
Counties around St. Clair County
3 of the 6 closest counties are windier at turbine height; the windiest, Clinton County, averages 5.65 m/s.
- Monroe County, IL: 5.05 m/s, 12,873 kWh, payback 40 years (19 mi)
- St. Louis city, MO: 5.05 m/s, 12,873 kWh, payback 54 years (21 mi)
- Madison County, IL: 5.57 m/s, 16,544 kWh, payback 31 years (25 mi)
- Clinton County, IL: 5.65 m/s, 17,126 kWh, payback 30 years (29 mi)
- Washington County, IL: 5.65 m/s, 17,126 kWh, payback 30 years (29 mi)
- Randolph County, IL: 4.69 m/s, 10,508 kWh, payback 50 years (29 mi)
Sun versus wind in St. Clair County
St. Clair County gets 4.18 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,221 kWh a year; one kW of the turbine above makes 1,287. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.1 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.