Wind Turbine Payback in Davidson County, TN
Wind turbine payback in Davidson 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 Davidson County, TN averages 4.41 m/s (9.9 mph). A 10 kW turbine there would make about 8,807 kWh a year, worth $1,215 at TN's 13.8¢/kWh. Against an installed cost of about $100,000, that is a payback of 82 years, and the turbine is built to last about 20.
What to do in Davidson County
A home turbine is not worth buying for savings in Davidson County unless your spot is far windier than the county average, 8.4 m/s at the hub against 4.41 m/s here. Per kW, solar panels would make about 1,235 kWh a year here against the turbine's 881, so get a solar quote first.
What would have to change
- Power would have to cost 57¢/kWh, 4.1 times what TN pays now.
- Or the average wind at the hub would have to be 8.4 m/s instead of 4.41. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of TN
Davidson County is the 1,810th 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 Davidson County
March is the strongest month here, at 5.27 m/s and about 1,220 kWh. July is the weakest, 3.17 m/s and 266 kWh, so the best month makes 4.6 times the worst. November to March brings in 57% of the year's output in Davidson County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 5.10 m/s | 1,124 kWh | $155 |
| February | 5.21 m/s | 1,075 kWh | $148 |
| March | 5.27 m/s | 1,220 kWh | $168 |
| April | 5.27 m/s | 1,186 kWh | $164 |
| May | 4.29 m/s | 690 kWh | $95 |
| June | 3.55 m/s | 372 kWh | $51 |
| July | 3.17 m/s | 266 kWh | $37 |
| August | 3.27 m/s | 296 kWh | $41 |
| September | 3.78 m/s | 453 kWh | $63 |
| October | 4.35 m/s | 719 kWh | $99 |
| November | 4.80 m/s | 919 kWh | $127 |
| December | 4.91 m/s | 1,012 kWh | $140 |
What a taller tower would buy
Measured at 10 m the wind in Davidson County averages 3.15 m/s; at 50 m it is 5.16 m/s. That gives a shear exponent of 0.307, typical of rough, sheltered ground: trees or buildings slow the low wind a lot. Going from 20 m to 50 m takes output from 6,060 to 13,629 kWh a year, 125% 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 | 3.89 m/s | 6,060 kWh | over 100 years |
| 30 m | 4.41 m/s | 8,813 kWh | 82 years |
| 40 m | 4.82 m/s | 11,331 kWh | 64 years |
| 50 m | 5.16 m/s | 13,629 kWh | 53 years |
Counties around Davidson County
3 of the 6 closest counties are windier at turbine height; the windiest, Cheatham County, averages 4.5 m/s.
- Cheatham County, TN: 4.5 m/s, 9,339 kWh, payback 78 years (19 mi)
- Williamson County, TN: 4.41 m/s, 8,807 kWh, payback 82 years (20 mi)
- Robertson County, TN: 4.5 m/s, 9,339 kWh, payback 78 years (25 mi)
- Wilson County, TN: 4.35 m/s, 8,460 kWh, payback 86 years (28 mi)
- Sumner County, TN: 4.45 m/s, 9,041 kWh, payback 80 years (28 mi)
- Rutherford County, TN: 4.35 m/s, 8,460 kWh, payback 86 years (30 mi)
Sun versus wind in Davidson County
Davidson County gets 4.23 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,235 kWh a year; one kW of the turbine above makes 881. Kilowatt for kilowatt, panels make 1.4 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.