Wind Turbine Payback in Union County, TN
Wind turbine payback in Union 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 Union County, TN averages 3.14 m/s (7 mph). A 10 kW turbine there would make about 3,034 kWh a year, worth $419 at TN's 13.8¢/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 Union County
A home turbine is not worth buying for savings in Union County unless your spot is far windier than the county average, 8.4 m/s at the hub against 3.14 m/s here. Per kW, solar panels would make about 1,232 kWh a year here against the turbine's 303, so get a solar quote first.
What would have to change
- Power would have to cost 165¢/kWh, 11.9 times what TN pays now.
- Or the average wind at the hub would have to be 8.4 m/s instead of 3.14. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of TN
Union County is the 2,952nd 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 Union County
March is the strongest month here, at 3.75 m/s and about 458 kWh. August is the weakest, 2.36 m/s and 92 kWh, so the best month makes 5.0 times the worst. November to March brings in 59% of the year's output in Union County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 3.65 m/s | 419 kWh | $58 |
| February | 3.78 m/s | 424 kWh | $59 |
| March | 3.75 m/s | 458 kWh | $63 |
| April | 3.68 m/s | 417 kWh | $58 |
| May | 3.02 m/s | 227 kWh | $31 |
| June | 2.63 m/s | 133 kWh | $18 |
| July | 2.42 m/s | 101 kWh | $14 |
| August | 2.36 m/s | 92 kWh | $13 |
| September | 2.63 m/s | 133 kWh | $18 |
| October | 3.05 m/s | 233 kWh | $32 |
| November | 3.26 m/s | 283 kWh | $39 |
| December | 3.42 m/s | 342 kWh | $47 |
What a taller tower would buy
Measured at 10 m the wind in Union County averages 1.93 m/s; at 50 m it is 3.93 m/s. That gives a shear exponent of 0.442, typical of rough, sheltered ground: trees or buildings slow the low wind a lot. Going from 20 m to 50 m takes output from 1,613 to 6,231 kWh a year, 286% 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 | 2.62 m/s | 1,613 kWh | over 100 years |
| 30 m | 3.14 m/s | 3,020 kWh | over 100 years |
| 40 m | 3.56 m/s | 4,574 kWh | over 100 years |
| 50 m | 3.93 m/s | 6,231 kWh | over 100 years |
Counties around Union County
2 of the 6 closest counties are windier at turbine height; the windiest, Knox County, averages 3.36 m/s.
- Claiborne County, TN: 3.14 m/s, 3,034 kWh, payback over 100 years (18 mi)
- Grainger County, TN: 3.14 m/s, 3,034 kWh, payback over 100 years (18 mi)
- Campbell County, TN: 3.11 m/s, 2,938 kWh, payback over 100 years (20 mi)
- Knox County, TN: 3.36 m/s, 3,794 kWh, payback over 100 years (21 mi)
- Anderson County, TN: 3.05 m/s, 2,751 kWh, payback over 100 years (23 mi)
- Jefferson County, TN: 3.36 m/s, 3,794 kWh, payback over 100 years (27 mi)
Sun versus wind in Union County
Union County gets 4.22 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,232 kWh a year; one kW of the turbine above makes 303. Kilowatt for kilowatt, panels make 4.1 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.