Wind Turbine Payback in Washington County, IL
Wind turbine payback in Washington 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 Washington County, IL averages 5.65 m/s (12.6 mph). A 10 kW turbine there would make about 17,126 kWh a year, worth $3,293 at IL's 19.23¢/kWh. Against an installed cost of about $100,000, that is a payback of 30 years, and the turbine is built to last about 20.
What to do in Washington County
A home turbine is not worth buying for savings in Washington County unless your spot is far windier than the county average, 6.8 m/s at the hub against 5.65 m/s here. Per kW, solar panels would make about 1,221 kWh a year here against the turbine's 1,713, so get a solar quote first.
What would have to change
- Power would have to cost 29¢/kWh, 1.5 times what IL pays now.
- Or the average wind at the hub would have to be 6.8 m/s instead of 5.65. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IL
Washington County is the 1,147th 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 Washington County
April is the strongest month here, at 6.66 m/s and about 2,020 kWh. July is the weakest, 4.20 m/s and 649 kWh, so the best month makes 3.1 times the worst. November to March brings in 53% of the year's output in Washington County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.38 m/s | 1,911 kWh | $367 |
| February | 6.34 m/s | 1,706 kWh | $328 |
| March | 6.48 m/s | 1,977 kWh | $380 |
| April | 6.66 m/s | 2,020 kWh | $388 |
| May | 5.66 m/s | 1,462 kWh | $281 |
| June | 4.86 m/s | 953 kWh | $183 |
| July | 4.20 m/s | 649 kWh | $125 |
| August | 4.24 m/s | 666 kWh | $128 |
| September | 4.73 m/s | 882 kWh | $170 |
| October | 5.85 m/s | 1,578 kWh | $303 |
| November | 6.32 m/s | 1,817 kWh | $349 |
| December | 6.19 m/s | 1,794 kWh | $345 |
What a taller tower would buy
Measured at 10 m the wind in Washington County averages 4.33 m/s; at 50 m it is 6.4 m/s. That gives a shear exponent of 0.243, typical of ordinary open country. Going from 20 m to 50 m takes output from 13,370 to 22,669 kWh a year, 70% 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 | 5.12 m/s | 13,370 kWh | 39 years |
| 30 m | 5.65 m/s | 17,147 kWh | 30 years |
| 40 m | 6.06 m/s | 20,165 kWh | 26 years |
| 50 m | 6.4 m/s | 22,669 kWh | 23 years |
Counties around Washington County
2 of the 6 closest counties are windier at turbine height; the windiest, Jefferson County, averages 5.71 m/s.
- Clinton County, IL: 5.65 m/s, 17,126 kWh, payback 30 years (17 mi)
- Perry County, IL: 5.34 m/s, 14,892 kWh, payback 35 years (19 mi)
- Jefferson County, IL: 5.71 m/s, 17,565 kWh, payback 30 years (27 mi)
- St. Clair County, IL: 5.05 m/s, 12,873 kWh, payback 40 years (29 mi)
- Randolph County, IL: 4.69 m/s, 10,508 kWh, payback 50 years (30 mi)
- Marion County, IL: 5.71 m/s, 17,565 kWh, payback 30 years (34 mi)
Sun versus wind in Washington County
Washington 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 1,713. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.4 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.