Wind Turbine Payback in Marshall County, IL
Wind turbine payback in Marshall 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 Marshall County, IL averages 6.03 m/s (13.5 mph). A 10 kW turbine there would make about 19,926 kWh a year, worth $3,832 at IL's 19.23¢/kWh. Against an installed cost of about $100,000, that is a payback of 26 years, and the turbine is built to last about 20.
What to do in Marshall County
A home turbine is not worth buying for savings in Marshall County unless your spot is far windier than the county average, 6.8 m/s at the hub against 6.03 m/s here. Per kW, solar panels would make about 1,162 kWh a year here against the turbine's 1,993, so get a solar quote first.
What would have to change
- Power would have to cost 25¢/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 6.03. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IL
Marshall County is the 791st 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 Marshall County
April is the strongest month here, at 7.02 m/s and about 2,232 kWh. August is the weakest, 4.58 m/s and 835 kWh, so the best month makes 2.7 times the worst. November to March brings in 50% of the year's output in Marshall County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.61 m/s | 2,054 kWh | $395 |
| February | 6.56 m/s | 1,830 kWh | $352 |
| March | 6.69 m/s | 2,109 kWh | $406 |
| April | 7.02 m/s | 2,232 kWh | $429 |
| May | 6.12 m/s | 1,752 kWh | $337 |
| June | 5.36 m/s | 1,234 kWh | $237 |
| July | 4.63 m/s | 859 kWh | $165 |
| August | 4.58 m/s | 835 kWh | $161 |
| September | 5.39 m/s | 1,255 kWh | $241 |
| October | 6.34 m/s | 1,886 kWh | $363 |
| November | 6.69 m/s | 2,041 kWh | $392 |
| December | 6.44 m/s | 1,954 kWh | $376 |
What a taller tower would buy
Measured at 10 m the wind in Marshall County averages 4.71 m/s; at 50 m it is 6.76 m/s. That gives a shear exponent of 0.225, typical of ordinary open country. Going from 20 m to 50 m takes output from 16,041 to 25,311 kWh a year, 58% 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 | 5.5 m/s | 16,041 kWh | 32 years |
| 30 m | 6.03 m/s | 19,897 kWh | 26 years |
| 40 m | 6.43 m/s | 22,883 kWh | 23 years |
| 50 m | 6.76 m/s | 25,311 kWh | 21 years |
Counties around Marshall County
None of the 6 closest counties is windier than Marshall County.
- Putnam County, IL: 6.03 m/s, 19,926 kWh, payback 26 years (12 mi)
- Woodford County, IL: 6.03 m/s, 19,926 kWh, payback 26 years (18 mi)
- Stark County, IL: 6.03 m/s, 19,926 kWh, payback 26 years (24 mi)
- Bureau County, IL: 5.98 m/s, 19,556 kWh, payback 27 years (27 mi)
- Peoria County, IL: 6.03 m/s, 19,926 kWh, payback 26 years (28 mi)
- LaSalle County, IL: 5.98 m/s, 19,556 kWh, payback 27 years (32 mi)
Sun versus wind in Marshall County
Marshall County gets 3.98 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,162 kWh a year; one kW of the turbine above makes 1,993. 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.