Wind Turbine Payback in Franklin County, IL
Wind turbine payback in Franklin 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 Franklin County, IL averages 5.51 m/s (12.3 mph). A 10 kW turbine there would make about 16,109 kWh a year, worth $3,098 at IL's 19.23¢/kWh. Against an installed cost of about $100,000, that is a payback of 32 years, and the turbine is built to last about 20.
What to do in Franklin County
A home turbine is not worth buying for savings in Franklin County unless your spot is far windier than the county average, 6.8 m/s at the hub against 5.51 m/s here. Per kW, solar panels would make about 1,229 kWh a year here against the turbine's 1,611, so get a solar quote first.
What would have to change
- Power would have to cost 31¢/kWh, 1.6 times what IL pays now.
- Or the average wind at the hub would have to be 6.8 m/s instead of 5.51. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IL
Franklin County is the 1,215th 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 Franklin County
April is the strongest month here, at 6.53 m/s and about 1,945 kWh. July is the weakest, 4.08 m/s and 595 kWh, so the best month makes 3.3 times the worst. November to March brings in 54% of the year's output in Franklin County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.28 m/s | 1,849 kWh | $356 |
| February | 6.25 m/s | 1,655 kWh | $318 |
| March | 6.41 m/s | 1,933 kWh | $372 |
| April | 6.53 m/s | 1,945 kWh | $374 |
| May | 5.51 m/s | 1,369 kWh | $263 |
| June | 4.65 m/s | 842 kWh | $162 |
| July | 4.08 m/s | 595 kWh | $114 |
| August | 4.13 m/s | 614 kWh | $118 |
| September | 4.59 m/s | 815 kWh | $157 |
| October | 5.64 m/s | 1,451 kWh | $279 |
| November | 6.10 m/s | 1,682 kWh | $323 |
| December | 6.04 m/s | 1,699 kWh | $327 |
What a taller tower would buy
Measured at 10 m the wind in Franklin County averages 4.21 m/s; at 50 m it is 6.25 m/s. That gives a shear exponent of 0.246, typical of ordinary open country. Going from 20 m to 50 m takes output from 12,458 to 21,558 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 | 4.99 m/s | 12,458 kWh | 42 years |
| 30 m | 5.51 m/s | 16,123 kWh | 32 years |
| 40 m | 5.92 m/s | 19,084 kWh | 27 years |
| 50 m | 6.25 m/s | 21,558 kWh | 24 years |
Counties around Franklin County
1 of the 6 closest counties is windier at turbine height; the windiest, Jefferson County, averages 5.71 m/s.
- Williamson County, IL: 4.82 m/s, 11,341 kWh, payback 46 years (18 mi)
- Jefferson County, IL: 5.71 m/s, 17,565 kWh, payback 30 years (21 mi)
- Hamilton County, IL: 5.51 m/s, 16,109 kWh, payback 32 years (22 mi)
- Perry County, IL: 5.34 m/s, 14,892 kWh, payback 35 years (25 mi)
- Saline County, IL: 5.51 m/s, 16,109 kWh, payback 32 years (27 mi)
- Jackson County, IL: 5.34 m/s, 14,892 kWh, payback 35 years (29 mi)
Sun versus wind in Franklin County
Franklin 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 1,611. 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.