Wind Turbine Payback in Rutherford County, TN
Wind turbine payback in Rutherford 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 Rutherford County, TN averages 4.35 m/s (9.7 mph). A 10 kW turbine there would make about 8,460 kWh a year, worth $1,167 at TN's 13.8¢/kWh. Against an installed cost of about $100,000, that is a payback of 86 years, and the turbine is built to last about 20.
What to do in Rutherford County
A home turbine is not worth buying for savings in Rutherford County unless your spot is far windier than the county average, 8.4 m/s at the hub against 4.35 m/s here. Per kW, solar panels would make about 1,261 kWh a year here against the turbine's 846, so get a solar quote first.
What would have to change
- Power would have to cost 59¢/kWh, 4.3 times what TN pays now.
- Or the average wind at the hub would have to be 8.4 m/s instead of 4.35. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of TN
Rutherford County is the 1,852nd 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 Rutherford County
March is the strongest month here, at 5.21 m/s and about 1,186 kWh. July is the weakest, 3.15 m/s and 261 kWh, so the best month makes 4.5 times the worst. November to March brings in 58% of the year's output in Rutherford County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 5.03 m/s | 1,081 kWh | $149 |
| February | 5.17 m/s | 1,053 kWh | $145 |
| March | 5.21 m/s | 1,186 kWh | $164 |
| April | 5.19 m/s | 1,138 kWh | $157 |
| May | 4.22 m/s | 658 kWh | $91 |
| June | 3.53 m/s | 365 kWh | $50 |
| July | 3.15 m/s | 261 kWh | $36 |
| August | 3.20 m/s | 276 kWh | $38 |
| September | 3.68 m/s | 419 kWh | $58 |
| October | 4.27 m/s | 678 kWh | $94 |
| November | 4.71 m/s | 875 kWh | $121 |
| December | 4.86 m/s | 984 kWh | $136 |
What a taller tower would buy
Measured at 10 m the wind in Rutherford County averages 3.12 m/s; at 50 m it is 5.08 m/s. That gives a shear exponent of 0.303, typical of rough, sheltered ground: trees or buildings slow the low wind a lot. Going from 20 m to 50 m takes output from 5,840 to 13,078 kWh a year, 124% 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 | 3.85 m/s | 5,840 kWh | over 100 years |
| 30 m | 4.35 m/s | 8,469 kWh | 86 years |
| 40 m | 4.75 m/s | 10,876 kWh | 67 years |
| 50 m | 5.08 m/s | 13,078 kWh | 55 years |
Counties around Rutherford County
2 of the 6 closest counties are windier at turbine height; the windiest, Williamson County, averages 4.41 m/s.
- Cannon County, TN: 4.35 m/s, 8,460 kWh, payback 86 years (20 mi)
- Wilson County, TN: 4.35 m/s, 8,460 kWh, payback 86 years (22 mi)
- Bedford County, TN: 4.2 m/s, 7,623 kWh, payback 95 years (23 mi)
- Williamson County, TN: 4.41 m/s, 8,807 kWh, payback 82 years (27 mi)
- Davidson County, TN: 4.41 m/s, 8,807 kWh, payback 82 years (30 mi)
- Coffee County, TN: 4.2 m/s, 7,623 kWh, payback 95 years (31 mi)
Sun versus wind in Rutherford County
Rutherford County gets 4.32 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,261 kWh a year; one kW of the turbine above makes 846. Kilowatt for kilowatt, panels make 1.5 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.