Wind Turbine Payback in Rock Island County, IL
Wind turbine payback in Rock Island 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 Rock Island County, IL averages 5.99 m/s (13.4 mph). A 10 kW turbine there would make about 19,630 kWh a year, worth $3,775 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 Rock Island County
A home turbine is not worth buying for savings in Rock Island County unless your spot is far windier than the county average, 6.8 m/s at the hub against 5.99 m/s here. Per kW, solar panels would make about 1,165 kWh a year here against the turbine's 1,963, 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 5.99. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IL
Rock Island County is the 858th 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 Rock Island County
April is the strongest month here, at 6.96 m/s and about 2,201 kWh. August is the weakest, 4.68 m/s and 885 kWh, so the best month makes 2.5 times the worst. November to March brings in 49% of the year's output in Rock Island County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.45 m/s | 1,955 kWh | $376 |
| February | 6.45 m/s | 1,766 kWh | $340 |
| March | 6.63 m/s | 2,066 kWh | $397 |
| April | 6.96 m/s | 2,201 kWh | $423 |
| May | 6.13 m/s | 1,753 kWh | $337 |
| June | 5.39 m/s | 1,252 kWh | $241 |
| July | 4.69 m/s | 894 kWh | $172 |
| August | 4.68 m/s | 885 kWh | $170 |
| September | 5.49 m/s | 1,315 kWh | $253 |
| October | 6.29 m/s | 1,854 kWh | $357 |
| November | 6.56 m/s | 1,962 kWh | $377 |
| December | 6.26 m/s | 1,837 kWh | $353 |
What a taller tower would buy
Measured at 10 m the wind in Rock Island County averages 4.67 m/s; at 50 m it is 6.73 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 15,793 to 25,093 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 | 5.47 m/s | 15,793 kWh | 33 years |
| 30 m | 5.99 m/s | 19,653 kWh | 27 years |
| 40 m | 6.4 m/s | 22,651 kWh | 23 years |
| 50 m | 6.73 m/s | 25,093 kWh | 21 years |
Counties around Rock Island County
2 of the 6 closest counties are windier at turbine height; the windiest, Mercer County, averages 6.02 m/s.
- Scott County, IA: 5.99 m/s, 19,630 kWh, payback 35 years (12 mi)
- Mercer County, IL: 6.02 m/s, 19,852 kWh, payback 26 years (20 mi)
- Henry County, IL: 5.99 m/s, 19,630 kWh, payback 27 years (24 mi)
- Muscatine County, IA: 5.99 m/s, 19,630 kWh, payback 35 years (28 mi)
- Clinton County, IA: 5.95 m/s, 19,334 kWh, payback 36 years (30 mi)
- Cedar County, IA: 6.01 m/s, 19,778 kWh, payback 35 years (36 mi)
Sun versus wind in Rock Island County
Rock Island County gets 3.99 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,165 kWh a year; one kW of the turbine above makes 1,963. 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.