Wind Turbine Payback in Lewis County, TN
Wind turbine payback in Lewis 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 Lewis County, TN averages 3.48 m/s (7.8 mph). A 10 kW turbine there would make about 4,250 kWh a year, worth $586 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 Lewis County
A home turbine is not worth buying for savings in Lewis County unless your spot is far windier than the county average, 8.4 m/s at the hub against 3.48 m/s here. Per kW, solar panels would make about 1,267 kWh a year here against the turbine's 425, so get a solar quote first.
What would have to change
- Power would have to cost 118¢/kWh, 8.5 times what TN pays now.
- Or the average wind at the hub would have to be 8.4 m/s instead of 3.48. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of TN
Lewis County is the 2,536th 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 Lewis County
March is the strongest month here, at 4.13 m/s and about 614 kWh. July is the weakest, 2.57 m/s and 128 kWh, so the best month makes 4.8 times the worst. November to March brings in 58% of the year's output in Lewis County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 3.99 m/s | 554 kWh | $76 |
| February | 4.14 m/s | 561 kWh | $77 |
| March | 4.13 m/s | 614 kWh | $85 |
| April | 4.07 m/s | 570 kWh | $79 |
| May | 3.36 m/s | 324 kWh | $45 |
| June | 2.84 m/s | 176 kWh | $24 |
| July | 2.57 m/s | 128 kWh | $18 |
| August | 2.67 m/s | 146 kWh | $20 |
| September | 3.03 m/s | 221 kWh | $30 |
| October | 3.44 m/s | 347 kWh | $48 |
| November | 3.73 m/s | 437 kWh | $60 |
| December | 3.83 m/s | 488 kWh | $67 |
What a taller tower would buy
Measured at 10 m the wind in Lewis County averages 2.16 m/s; at 50 m it is 4.34 m/s. That gives a shear exponent of 0.434, typical of rough, sheltered ground: trees or buildings slow the low wind a lot. Going from 20 m to 50 m takes output from 2,359 to 8,403 kWh a year, 256% 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 | 2.92 m/s | 2,359 kWh | over 100 years |
| 30 m | 3.48 m/s | 4,238 kWh | over 100 years |
| 40 m | 3.94 m/s | 6,277 kWh | over 100 years |
| 50 m | 4.34 m/s | 8,403 kWh | 86 years |
Counties around Lewis County
4 of the 6 closest counties are windier at turbine height; the windiest, Maury County, averages 4.18 m/s.
- Hickman County, TN: 3.51 m/s, 4,368 kWh, payback over 100 years (19 mi)
- Lawrence County, TN: 4.02 m/s, 6,678 kWh, payback over 100 years (22 mi)
- Perry County, TN: 3.28 m/s, 3,506 kWh, payback over 100 years (23 mi)
- Maury County, TN: 4.18 m/s, 7,515 kWh, payback 96 years (24 mi)
- Wayne County, TN: 3.44 m/s, 4,094 kWh, payback over 100 years (27 mi)
- Giles County, TN: 3.99 m/s, 6,527 kWh, payback over 100 years (34 mi)
Sun versus wind in Lewis County
Lewis County gets 4.34 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,267 kWh a year; one kW of the turbine above makes 425. Kilowatt for kilowatt, panels make 3.0 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.