Wind Turbine Payback in Marshall County, TN
Wind turbine payback in Marshall 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 Marshall County, TN averages 4.18 m/s (9.4 mph). A 10 kW turbine there would make about 7,515 kWh a year, worth $1,037 at TN's 13.8¢/kWh. Against an installed cost of about $100,000, that is a payback of 96 years, and the turbine is built to last about 20.
What to do in Marshall County
A home turbine is not worth buying for savings in Marshall County unless your spot is far windier than the county average, 8.4 m/s at the hub against 4.18 m/s here. Per kW, solar panels would make about 1,261 kWh a year here against the turbine's 752, so get a solar quote first.
What would have to change
- Power would have to cost 67¢/kWh, 4.8 times what TN pays now.
- Or the average wind at the hub would have to be 8.4 m/s instead of 4.18. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of TN
Marshall County is the 1,957th 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 Marshall County
March is the strongest month here, at 5.00 m/s and about 1,064 kWh. July is the weakest, 3.03 m/s and 229 kWh, so the best month makes 4.6 times the worst. November to March brings in 58% of the year's output in Marshall County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 4.85 m/s | 978 kWh | $135 |
| February | 4.99 m/s | 957 kWh | $132 |
| March | 5.00 m/s | 1,064 kWh | $147 |
| April | 4.96 m/s | 1,006 kWh | $139 |
| May | 4.07 m/s | 587 kWh | $81 |
| June | 3.37 m/s | 315 kWh | $43 |
| July | 3.03 m/s | 229 kWh | $32 |
| August | 3.13 m/s | 255 kWh | $35 |
| September | 3.62 m/s | 395 kWh | $55 |
| October | 4.13 m/s | 617 kWh | $85 |
| November | 4.55 m/s | 792 kWh | $109 |
| December | 4.66 m/s | 876 kWh | $121 |
What a taller tower would buy
Measured at 10 m the wind in Marshall County averages 2.94 m/s; at 50 m it is 4.93 m/s. That gives a shear exponent of 0.321, typical of rough, sheltered ground: trees or buildings slow the low wind a lot. Going from 20 m to 50 m takes output from 5,050 to 12,065 kWh a year, 139% 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 | 3.67 m/s | 5,050 kWh | over 100 years |
| 30 m | 4.18 m/s | 7,539 kWh | 96 years |
| 40 m | 4.59 m/s | 9,880 kWh | 73 years |
| 50 m | 4.93 m/s | 12,065 kWh | 60 years |
Counties around Marshall County
3 of the 6 closest counties are windier at turbine height; the windiest, Williamson County, averages 4.41 m/s.
- Bedford County, TN: 4.2 m/s, 7,623 kWh, payback 95 years (18 mi)
- Maury County, TN: 4.18 m/s, 7,515 kWh, payback 96 years (20 mi)
- Giles County, TN: 3.99 m/s, 6,527 kWh, payback over 100 years (24 mi)
- Lincoln County, TN: 3.99 m/s, 6,527 kWh, payback over 100 years (25 mi)
- Moore County, TN: 4.2 m/s, 7,623 kWh, payback 95 years (26 mi)
- Williamson County, TN: 4.41 m/s, 8,807 kWh, payback 82 years (30 mi)
Sun versus wind in Marshall County
Marshall 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 752. Kilowatt for kilowatt, panels make 1.7 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.