Wind Turbine Payback in Franklin County, TN
Wind turbine payback in Franklin 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 Franklin County, TN averages 3.8 m/s (8.5 mph). A 10 kW turbine there would make about 5,614 kWh a year, worth $775 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 Franklin County
A home turbine is not worth buying for savings in Franklin County unless your spot is far windier than the county average, 8.4 m/s at the hub against 3.8 m/s here. Per kW, solar panels would make about 1,261 kWh a year here against the turbine's 561, so get a solar quote first.
What would have to change
- Power would have to cost 89¢/kWh, 6.5 times what TN pays now.
- Or the average wind at the hub would have to be 8.4 m/s instead of 3.8. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of TN
Franklin County is the 2,206th 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 Franklin County
March is the strongest month here, at 4.53 m/s and about 807 kWh. July is the weakest, 2.74 m/s and 162 kWh, so the best month makes 5.0 times the worst. November to March brings in 59% of the year's output in Franklin County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 4.42 m/s | 752 kWh | $104 |
| February | 4.55 m/s | 740 kWh | $102 |
| March | 4.53 m/s | 807 kWh | $111 |
| April | 4.46 m/s | 748 kWh | $103 |
| May | 3.66 m/s | 423 kWh | $58 |
| June | 3.06 m/s | 229 kWh | $32 |
| July | 2.74 m/s | 162 kWh | $22 |
| August | 2.83 m/s | 180 kWh | $25 |
| September | 3.29 m/s | 291 kWh | $40 |
| October | 3.77 m/s | 463 kWh | $64 |
| November | 4.12 m/s | 594 kWh | $82 |
| December | 4.25 m/s | 671 kWh | $93 |
What a taller tower would buy
Measured at 10 m the wind in Franklin County averages 2.59 m/s; at 50 m it is 4.54 m/s. That gives a shear exponent of 0.349, typical of rough, sheltered ground: trees or buildings slow the low wind a lot. Going from 20 m to 50 m takes output from 3,568 to 9,580 kWh a year, 168% 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 | 3.3 m/s | 3,568 kWh | over 100 years |
| 30 m | 3.8 m/s | 5,608 kWh | over 100 years |
| 40 m | 4.2 m/s | 7,623 kWh | 95 years |
| 50 m | 4.54 m/s | 9,580 kWh | 76 years |
Counties around Franklin County
3 of the 6 closest counties are windier at turbine height; the windiest, Moore County, averages 4.2 m/s.
- Moore County, TN: 4.2 m/s, 7,623 kWh, payback 95 years (17 mi)
- Coffee County, TN: 4.2 m/s, 7,623 kWh, payback 95 years (23 mi)
- Grundy County, TN: 3.42 m/s, 4,018 kWh, payback over 100 years (27 mi)
- Marion County, TN: 3.22 m/s, 3,299 kWh, payback over 100 years (28 mi)
- Jackson County, AL: 3.8 m/s, 5,614 kWh, payback over 100 years (28 mi)
- Lincoln County, TN: 3.99 m/s, 6,527 kWh, payback over 100 years (28 mi)
Sun versus wind in Franklin County
Franklin 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 561. Kilowatt for kilowatt, panels make 2.2 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.