Wind Turbine Payback in Stephenson County, IL
Wind turbine payback in Stephenson 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 Stephenson County, IL averages 5.98 m/s (13.4 mph). A 10 kW turbine there would make about 19,556 kWh a year, worth $3,761 at IL's 19.23¢/kWh. Against an installed cost of about $100,000, that is a payback of 27 years, and the turbine is built to last about 20.
What to do in Stephenson County
A home turbine is not worth buying for savings in Stephenson County unless your spot is far windier than the county average, 6.8 m/s at the hub against 5.98 m/s here. Per kW, solar panels would make about 1,145 kWh a year here against the turbine's 1,956, so get a solar quote first.
What would have to change
- Power would have to cost 26¢/kWh, 1.3 times what IL pays now.
- Or the average wind at the hub would have to be 6.8 m/s instead of 5.98. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IL
Stephenson County is the 873rd 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 Stephenson County
April is the strongest month here, at 6.85 m/s and about 2,133 kWh. August is the weakest, 4.62 m/s and 856 kWh, so the best month makes 2.5 times the worst. November to March brings in 49% of the year's output in Stephenson County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.54 m/s | 2,011 kWh | $387 |
| February | 6.62 m/s | 1,861 kWh | $358 |
| March | 6.51 m/s | 1,994 kWh | $383 |
| April | 6.85 m/s | 2,133 kWh | $410 |
| May | 6.05 m/s | 1,703 kWh | $327 |
| June | 5.31 m/s | 1,205 kWh | $232 |
| July | 4.73 m/s | 913 kWh | $176 |
| August | 4.62 m/s | 856 kWh | $165 |
| September | 5.50 m/s | 1,320 kWh | $254 |
| October | 6.28 m/s | 1,849 kWh | $356 |
| November | 6.50 m/s | 1,924 kWh | $370 |
| December | 6.29 m/s | 1,854 kWh | $357 |
What a taller tower would buy
Measured at 10 m the wind in Stephenson County averages 4.66 m/s; at 50 m it is 6.71 m/s. That gives a shear exponent of 0.227, typical of ordinary open country. Going from 20 m to 50 m takes output from 15,676 to 24,947 kWh a year, 59% 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 | 5.45 m/s | 15,676 kWh | 33 years |
| 30 m | 5.98 m/s | 19,521 kWh | 27 years |
| 40 m | 6.38 m/s | 22,511 kWh | 23 years |
| 50 m | 6.71 m/s | 24,947 kWh | 21 years |
Counties around Stephenson County
None of the 6 closest counties is windier than Stephenson County.
- Green County, WI: 5.98 m/s, 19,556 kWh, payback 27 years (23 mi)
- Carroll County, IL: 5.92 m/s, 19,112 kWh, payback 27 years (23 mi)
- Winnebago County, IL: 5.98 m/s, 19,556 kWh, payback 27 years (26 mi)
- Ogle County, IL: 5.97 m/s, 19,482 kWh, payback 27 years (28 mi)
- Jo Daviess County, IL: 5.96 m/s, 19,408 kWh, payback 27 years (28 mi)
- Lafayette County, WI: 5.96 m/s, 19,408 kWh, payback 27 years (32 mi)
Sun versus wind in Stephenson County
Stephenson County gets 3.92 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,145 kWh a year; one kW of the turbine above makes 1,956. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.7 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.