Wind Turbine Payback in Cass County, IL
Wind turbine payback in Cass 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 Cass County, IL averages 5.88 m/s (13.2 mph). A 10 kW turbine there would make about 18,816 kWh a year, worth $3,618 at IL's 19.23¢/kWh. Against an installed cost of about $100,000, that is a payback of 28 years, and the turbine is built to last about 20.
What to do in Cass County
A home turbine is not worth buying for savings in Cass County unless your spot is far windier than the county average, 6.8 m/s at the hub against 5.88 m/s here. Per kW, solar panels would make about 1,203 kWh a year here against the turbine's 1,882, so get a solar quote first.
What would have to change
- Power would have to cost 27¢/kWh, 1.4 times what IL pays now.
- Or the average wind at the hub would have to be 6.8 m/s instead of 5.88. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of IL
Cass County is the 1,013th 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 Cass County
April is the strongest month here, at 6.84 m/s and about 2,129 kWh. July is the weakest, 4.49 m/s and 788 kWh, so the best month makes 2.7 times the worst. November to March brings in 51% of the year's output in Cass County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.51 m/s | 1,996 kWh | $384 |
| February | 6.44 m/s | 1,763 kWh | $339 |
| March | 6.58 m/s | 2,040 kWh | $392 |
| April | 6.84 m/s | 2,129 kWh | $409 |
| May | 5.90 m/s | 1,611 kWh | $310 |
| June | 5.21 m/s | 1,148 kWh | $221 |
| July | 4.49 m/s | 788 kWh | $152 |
| August | 4.52 m/s | 802 kWh | $154 |
| September | 5.09 m/s | 1,082 kWh | $208 |
| October | 6.14 m/s | 1,762 kWh | $339 |
| November | 6.54 m/s | 1,948 kWh | $375 |
| December | 6.34 m/s | 1,890 kWh | $363 |
What a taller tower would buy
Measured at 10 m the wind in Cass County averages 4.55 m/s; at 50 m it is 6.63 m/s. That gives a shear exponent of 0.234, typical of ordinary open country. Going from 20 m to 50 m takes output from 14,966 to 24,362 kWh a year, 63% 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 | 5.35 m/s | 14,966 kWh | 35 years |
| 30 m | 5.88 m/s | 18,839 kWh | 28 years |
| 40 m | 6.29 m/s | 21,875 kWh | 24 years |
| 50 m | 6.63 m/s | 24,362 kWh | 21 years |
Counties around Cass County
None of the 6 closest counties is windier than Cass County.
- Morgan County, IL: 5.84 m/s, 18,521 kWh, payback 28 years (18 mi)
- Schuyler County, IL: 5.85 m/s, 18,595 kWh, payback 28 years (23 mi)
- Menard County, IL: 5.88 m/s, 18,816 kWh, payback 28 years (24 mi)
- Mason County, IL: 5.88 m/s, 18,816 kWh, payback 28 years (26 mi)
- Scott County, IL: 5.67 m/s, 17,272 kWh, payback 30 years (26 mi)
- Brown County, IL: 5.85 m/s, 18,595 kWh, payback 28 years (27 mi)
Sun versus wind in Cass County
Cass County gets 4.12 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,203 kWh a year; one kW of the turbine above makes 1,882. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.6 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.