Wind Turbine Payback in Marion County, TN
Wind turbine payback in Marion 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 Marion County, TN averages 3.22 m/s (7.2 mph). A 10 kW turbine there would make about 3,299 kWh a year, worth $455 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 Marion County
A home turbine is not worth buying for savings in Marion County unless your spot is far windier than the county average, 8.4 m/s at the hub against 3.22 m/s here. Per kW, solar panels would make about 1,253 kWh a year here against the turbine's 330, so get a solar quote first.
What would have to change
- Power would have to cost 152¢/kWh, 11.0 times what TN pays now.
- Or the average wind at the hub would have to be 8.4 m/s instead of 3.22. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of TN
Marion County is the 2,857th 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 Marion County
March is the strongest month here, at 3.82 m/s and about 484 kWh. July is the weakest, 2.39 m/s and 96 kWh, so the best month makes 5.0 times the worst. November to March brings in 59% of the year's output in Marion County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 3.74 m/s | 452 kWh | $62 |
| February | 3.84 m/s | 445 kWh | $61 |
| March | 3.82 m/s | 484 kWh | $67 |
| April | 3.76 m/s | 447 kWh | $62 |
| May | 3.09 m/s | 243 kWh | $34 |
| June | 2.61 m/s | 131 kWh | $18 |
| July | 2.39 m/s | 96 kWh | $13 |
| August | 2.41 m/s | 100 kWh | $14 |
| September | 2.76 m/s | 159 kWh | $22 |
| October | 3.18 m/s | 269 kWh | $37 |
| November | 3.45 m/s | 339 kWh | $47 |
| December | 3.54 m/s | 383 kWh | $53 |
What a taller tower would buy
Measured at 10 m the wind in Marion County averages 2.01 m/s; at 50 m it is 4 m/s. That gives a shear exponent of 0.428, typical of rough, sheltered ground: trees or buildings slow the low wind a lot. Going from 20 m to 50 m takes output from 1,803 to 6,577 kWh a year, 265% 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 | 2.7 m/s | 1,803 kWh | over 100 years |
| 30 m | 3.21 m/s | 3,280 kWh | over 100 years |
| 40 m | 3.64 m/s | 4,886 kWh | over 100 years |
| 50 m | 4 m/s | 6,577 kWh | over 100 years |
Counties around Marion County
3 of the 6 closest counties are windier at turbine height; the windiest, Franklin County, averages 3.8 m/s.
- Grundy County, TN: 3.42 m/s, 4,018 kWh, payback over 100 years (19 mi)
- Dade County, GA: 3.22 m/s, 3,299 kWh, payback over 100 years (20 mi)
- Sequatchie County, TN: 3.42 m/s, 4,018 kWh, payback over 100 years (20 mi)
- Hamilton County, TN: 3.17 m/s, 3,132 kWh, payback over 100 years (23 mi)
- Franklin County, TN: 3.8 m/s, 5,614 kWh, payback over 100 years (28 mi)
- Catoosa County, GA: 3.17 m/s, 3,132 kWh, payback over 100 years (31 mi)
Sun versus wind in Marion County
Marion County gets 4.29 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,253 kWh a year; one kW of the turbine above makes 330. Kilowatt for kilowatt, panels make 3.8 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.