Wind Turbine Payback in Putnam County, TN
Wind turbine payback in Putnam 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 Putnam County, TN averages 3.44 m/s (7.7 mph). A 10 kW turbine there would make about 4,094 kWh a year, worth $565 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 Putnam County
A home turbine is not worth buying for savings in Putnam County unless your spot is far windier than the county average, 8.4 m/s at the hub against 3.44 m/s here. Per kW, solar panels would make about 1,226 kWh a year here against the turbine's 409, so get a solar quote first.
What would have to change
- Power would have to cost 122¢/kWh, 8.8 times what TN pays now.
- Or the average wind at the hub would have to be 8.4 m/s instead of 3.44. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of TN
Putnam County is the 2,573rd 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 Putnam County
March is the strongest month here, at 4.08 m/s and about 595 kWh. July is the weakest, 2.56 m/s and 126 kWh, so the best month makes 4.7 times the worst. November to March brings in 59% of the year's output in Putnam County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 3.98 m/s | 550 kWh | $76 |
| February | 4.13 m/s | 557 kWh | $77 |
| March | 4.08 m/s | 595 kWh | $82 |
| April | 4.02 m/s | 549 kWh | $76 |
| May | 3.30 m/s | 302 kWh | $42 |
| June | 2.83 m/s | 174 kWh | $24 |
| July | 2.56 m/s | 126 kWh | $17 |
| August | 2.60 m/s | 133 kWh | $18 |
| September | 2.93 m/s | 198 kWh | $27 |
| October | 3.38 m/s | 327 kWh | $45 |
| November | 3.69 m/s | 421 kWh | $58 |
| December | 3.83 m/s | 487 kWh | $67 |
What a taller tower would buy
Measured at 10 m the wind in Putnam County averages 2.16 m/s; at 50 m it is 4.27 m/s. That gives a shear exponent of 0.423, typical of rough, sheltered ground: trees or buildings slow the low wind a lot. Going from 20 m to 50 m takes output from 2,309 to 8,008 kWh a year, 247% 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 | 2.9 m/s | 2,309 kWh | over 100 years |
| 30 m | 3.44 m/s | 4,095 kWh | over 100 years |
| 40 m | 3.89 m/s | 6,015 kWh | over 100 years |
| 50 m | 4.27 m/s | 8,008 kWh | 91 years |
Counties around Putnam County
3 of the 6 closest counties are windier at turbine height; the windiest, Smith County, averages 4.45 m/s.
- White County, TN: 3.44 m/s, 4,094 kWh, payback over 100 years (15 mi)
- Jackson County, TN: 3.62 m/s, 4,820 kWh, payback over 100 years (18 mi)
- Overton County, TN: 3.41 m/s, 3,980 kWh, payback over 100 years (18 mi)
- DeKalb County, TN: 3.44 m/s, 4,094 kWh, payback over 100 years (22 mi)
- Smith County, TN: 4.45 m/s, 9,041 kWh, payback 80 years (26 mi)
- Clay County, TN: 3.62 m/s, 4,820 kWh, payback over 100 years (28 mi)
Sun versus wind in Putnam County
Putnam County gets 4.2 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,226 kWh a year; one kW of the turbine above makes 409. Kilowatt for kilowatt, panels make 3.0 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.