Wind Turbine Payback in Stillwater County, MT
Wind turbine payback in Stillwater 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 Stillwater County, MT averages 5.8 m/s (13 mph). A 10 kW turbine there would make about 18,226 kWh a year, worth $2,575 at MT's 14.13¢/kWh. Against an installed cost of about $100,000, that is a payback of 39 years, and the turbine is built to last about 20.
What to do in Stillwater County
A home turbine is not worth buying for savings in Stillwater County unless your spot is far windier than the county average, 8.2 m/s at the hub against 5.8 m/s here. Per kW, solar panels would make about 1,203 kWh a year here against the turbine's 1,823, so get a solar quote first.
What would have to change
- Power would have to cost 27¢/kWh, 1.9 times what MT pays now.
- Or the average wind at the hub would have to be 8.2 m/s instead of 5.8. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of MT
Stillwater County is the 1,064th windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. The windiest in MT is Fallon County at 6.64 m/s, payback 29 years.
Month by month in Stillwater County
January is the strongest month here, at 7.93 m/s and about 2,838 kWh. July is the weakest, 4.11 m/s and 608 kWh, so the best month makes 4.7 times the worst. November to March brings in 62% of the year's output in Stillwater County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 7.93 m/s | 2,838 kWh | $401 |
| February | 6.82 m/s | 1,976 kWh | $279 |
| March | 6.31 m/s | 1,871 kWh | $264 |
| April | 5.50 m/s | 1,320 kWh | $187 |
| May | 4.84 m/s | 977 kWh | $138 |
| June | 4.51 m/s | 771 kWh | $109 |
| July | 4.11 m/s | 608 kWh | $86 |
| August | 4.26 m/s | 674 kWh | $95 |
| September | 4.86 m/s | 955 kWh | $135 |
| October | 6.06 m/s | 1,708 kWh | $241 |
| November | 6.99 m/s | 2,217 kWh | $313 |
| December | 7.40 m/s | 2,535 kWh | $358 |
What a taller tower would buy
Measured at 10 m the wind in Stillwater County averages 4.52 m/s; at 50 m it is 6.51 m/s. That gives a shear exponent of 0.227, typical of ordinary open country. Going from 20 m to 50 m takes output from 14,520 to 23,481 kWh a year, 62% 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 | 5.29 m/s | 14,520 kWh | 49 years |
| 30 m | 5.8 m/s | 18,206 kWh | 39 years |
| 40 m | 6.19 m/s | 21,102 kWh | 34 years |
| 50 m | 6.51 m/s | 23,481 kWh | 30 years |
Counties around Stillwater County
3 of the 6 closest counties are windier at turbine height; the windiest, Golden Valley County, averages 6 m/s.
- Sweet Grass County, MT: 5.94 m/s, 19,260 kWh, payback 37 years (29 mi)
- Carbon County, MT: 4.41 m/s, 8,807 kWh, payback 80 years (35 mi)
- Golden Valley County, MT: 6 m/s, 19,704 kWh, payback 36 years (51 mi)
- Yellowstone County, MT: 5.74 m/s, 17,785 kWh, payback 40 years (57 mi)
- Park County, MT: 4.68 m/s, 10,445 kWh, payback 68 years (57 mi)
- Wheatland County, MT: 5.89 m/s, 18,890 kWh, payback 38 years (62 mi)
Sun versus wind in Stillwater County
Stillwater County gets 4.12 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,203 kWh a year; one kW of the turbine above makes 1,823. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.5 times. 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.