Wind Turbine Payback in St. Clair County, AL
Wind turbine payback in St. Clair 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 St. Clair County, AL averages 3.21 m/s (7.2 mph). A 10 kW turbine there would make about 3,265 kWh a year, worth $539 at AL's 16.51¢/kWh. Against an installed cost of about $100,000, that is a payback of over 100 years, and the turbine is built to last about 20.
What to do in St. Clair County
A home turbine is not worth buying for savings in St. Clair County unless your spot is far windier than the county average, 7.5 m/s at the hub against 3.21 m/s here. Per kW, solar panels would make about 1,308 kWh a year here against the turbine's 327, so get a solar quote first.
What would have to change
- Power would have to cost 153¢/kWh, 9.3 times what AL pays now.
- Or the average wind at the hub would have to be 7.5 m/s instead of 3.21. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of AL
St. Clair County is the 2,874th windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. The windiest in AL is Mobile County at 4.72 m/s, payback 57 years.
Month by month in St. Clair County
March is the strongest month here, at 3.73 m/s and about 449 kWh. July is the weakest, 2.41 m/s and 100 kWh, so the best month makes 4.5 times the worst. November to March brings in 57% of the year's output in St. Clair County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 3.62 m/s | 408 kWh | $67 |
| February | 3.70 m/s | 395 kWh | $65 |
| March | 3.73 m/s | 449 kWh | $74 |
| April | 3.68 m/s | 418 kWh | $69 |
| May | 3.11 m/s | 249 kWh | $41 |
| June | 2.64 m/s | 137 kWh | $23 |
| July | 2.41 m/s | 100 kWh | $17 |
| August | 2.48 m/s | 111 kWh | $18 |
| September | 2.93 m/s | 198 kWh | $33 |
| October | 3.26 m/s | 291 kWh | $48 |
| November | 3.49 m/s | 352 kWh | $58 |
| December | 3.51 m/s | 369 kWh | $61 |
What a taller tower would buy
Measured at 10 m the wind in St. Clair County averages 1.97 m/s; at 50 m it is 4.03 m/s. That gives a shear exponent of 0.445, typical of rough, sheltered ground: trees or buildings slow the low wind a lot. Going from 20 m to 50 m takes output from 1,751 to 6,729 kWh a year, 284% 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 | 2.68 m/s | 1,751 kWh | over 100 years |
| 30 m | 3.21 m/s | 3,267 kWh | over 100 years |
| 40 m | 3.65 m/s | 4,944 kWh | over 100 years |
| 50 m | 4.03 m/s | 6,729 kWh | 90 years |
Counties around St. Clair County
3 of the 6 closest counties are windier at turbine height; the windiest, Etowah County, averages 3.3 m/s.
- Blount County, AL: 3.23 m/s, 3,333 kWh, payback over 100 years (23 mi)
- Talladega County, AL: 3.21 m/s, 3,265 kWh, payback over 100 years (25 mi)
- Etowah County, AL: 3.3 m/s, 3,577 kWh, payback over 100 years (28 mi)
- Calhoun County, AL: 3.22 m/s, 3,299 kWh, payback over 100 years (28 mi)
- Jefferson County, AL: 3.14 m/s, 3,034 kWh, payback over 100 years (36 mi)
- Shelby County, AL: 3.14 m/s, 3,034 kWh, payback over 100 years (37 mi)
Sun versus wind in St. Clair County
St. Clair County gets 4.48 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,308 kWh a year; one kW of the turbine above makes 327. Kilowatt for kilowatt, panels make 4.0 times as much here as the turbine. 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.