Wind Turbine Payback in Polk County, TN
Wind turbine payback in Polk 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 Polk County, TN averages 3.24 m/s (7.2 mph). A 10 kW turbine there would make about 3,367 kWh a year, worth $465 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 Polk County
A home turbine is not worth buying for savings in Polk County unless your spot is far windier than the county average, 8.4 m/s at the hub against 3.24 m/s here. Per kW, solar panels would make about 1,261 kWh a year here against the turbine's 337, so get a solar quote first.
What would have to change
- Power would have to cost 149¢/kWh, 10.8 times what TN pays now.
- Or the average wind at the hub would have to be 8.4 m/s instead of 3.24. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of TN
Polk County is the 2,831st 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 Polk County
March is the strongest month here, at 3.80 m/s and about 477 kWh. July is the weakest, 2.42 m/s and 101 kWh, so the best month makes 4.7 times the worst. November to March brings in 59% of the year's output in Polk County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 3.70 m/s | 440 kWh | $61 |
| February | 3.81 m/s | 434 kWh | $60 |
| March | 3.80 m/s | 477 kWh | $66 |
| April | 3.74 m/s | 441 kWh | $61 |
| May | 3.13 m/s | 255 kWh | $35 |
| June | 2.63 m/s | 134 kWh | $18 |
| July | 2.42 m/s | 101 kWh | $14 |
| August | 2.46 m/s | 108 kWh | $15 |
| September | 2.82 m/s | 173 kWh | $24 |
| October | 3.25 m/s | 289 kWh | $40 |
| November | 3.52 m/s | 363 kWh | $50 |
| December | 3.62 m/s | 408 kWh | $56 |
What a taller tower would buy
Measured at 10 m the wind in Polk County averages 1.99 m/s; at 50 m it is 4.07 m/s. That gives a shear exponent of 0.445, typical of rough, sheltered ground: trees or buildings slow the low wind a lot. Going from 20 m to 50 m takes output from 1,814 to 6,934 kWh a year, 282% 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 | 2.71 m/s | 1,814 kWh | over 100 years |
| 30 m | 3.24 m/s | 3,376 kWh | over 100 years |
| 40 m | 3.69 m/s | 5,100 kWh | over 100 years |
| 50 m | 4.07 m/s | 6,934 kWh | over 100 years |
Counties around Polk County
None of the 6 closest counties is windier than Polk County.
- Bradley County, TN: 3.17 m/s, 3,132 kWh, payback over 100 years (18 mi)
- Fannin County, GA: 3.24 m/s, 3,367 kWh, payback over 100 years (21 mi)
- McMinn County, TN: 3.07 m/s, 2,813 kWh, payback over 100 years (22 mi)
- Murray County, GA: 3.17 m/s, 3,132 kWh, payback over 100 years (24 mi)
- Cherokee County, NC: 3.11 m/s, 2,938 kWh, payback over 100 years (27 mi)
- Monroe County, TN: 3.07 m/s, 2,813 kWh, payback over 100 years (29 mi)
Sun versus wind in Polk County
Polk 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 337. Kilowatt for kilowatt, panels make 3.7 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.