Wind Turbine Payback in Carroll County, TN
Wind turbine payback in Carroll 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 Carroll County, TN averages 5.09 m/s (11.4 mph). A 10 kW turbine there would make about 13,146 kWh a year, worth $1,814 at TN's 13.8¢/kWh. Against an installed cost of about $100,000, that is a payback of 55 years, and the turbine is built to last about 20.
What to do in Carroll County
A home turbine is not worth buying for savings in Carroll County unless your spot is far windier than the county average, 8.4 m/s at the hub against 5.09 m/s here. Per kW, solar panels would make about 1,279 kWh a year here against the turbine's 1,315, so get a solar quote first.
What would have to change
- Power would have to cost 38¢/kWh, 2.8 times what TN pays now.
- Or the average wind at the hub would have to be 8.4 m/s instead of 5.09. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of TN
Carroll County is the 1,408th windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. The windiest in TN is Lake County at 5.54 m/s, payback 44 years.
Month by month in Carroll County
April is the strongest month here, at 6.09 m/s and about 1,677 kWh. July is the weakest, 3.76 m/s and 461 kWh, so the best month makes 3.6 times the worst. November to March brings in 55% of the year's output in Carroll County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 5.78 m/s | 1,535 kWh | $212 |
| February | 5.88 m/s | 1,441 kWh | $199 |
| March | 5.97 m/s | 1,655 kWh | $228 |
| April | 6.09 m/s | 1,677 kWh | $231 |
| May | 5.07 m/s | 1,105 kWh | $152 |
| June | 4.15 m/s | 606 kWh | $84 |
| July | 3.76 m/s | 461 kWh | $64 |
| August | 3.82 m/s | 485 kWh | $67 |
| September | 4.37 m/s | 705 kWh | $97 |
| October | 5.06 m/s | 1,100 kWh | $152 |
| November | 5.56 m/s | 1,354 kWh | $187 |
| December | 5.59 m/s | 1,415 kWh | $195 |
What a taller tower would buy
Measured at 10 m the wind in Carroll County averages 3.81 m/s; at 50 m it is 5.82 m/s. That gives a shear exponent of 0.263, typical of ordinary open country. Going from 20 m to 50 m takes output from 9,785 to 18,374 kWh a year, 88% 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 | 4.57 m/s | 9,785 kWh | 74 years |
| 30 m | 5.09 m/s | 13,135 kWh | 55 years |
| 40 m | 5.49 m/s | 15,952 kWh | 45 years |
| 50 m | 5.82 m/s | 18,374 kWh | 39 years |
Counties around Carroll County
1 of the 6 closest counties is windier at turbine height; the windiest, Weakley County, averages 5.26 m/s.
- Henderson County, TN: 3.28 m/s, 3,506 kWh, payback over 100 years (22 mi)
- Benton County, TN: 3.61 m/s, 4,778 kWh, payback over 100 years (23 mi)
- Henry County, TN: 4.17 m/s, 7,461 kWh, payback 97 years (26 mi)
- Gibson County, TN: 5.09 m/s, 13,146 kWh, payback 55 years (27 mi)
- Weakley County, TN: 5.26 m/s, 14,327 kWh, payback 51 years (28 mi)
- Decatur County, TN: 3.28 m/s, 3,506 kWh, payback over 100 years (32 mi)
Sun versus wind in Carroll County
Carroll County gets 4.38 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,279 kWh a year; one kW of the turbine above makes 1,315. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.0 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.