Wind Turbine Payback in Sweet Grass County, MT
Wind turbine payback in Sweet Grass 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 Sweet Grass County, MT averages 5.94 m/s (13.3 mph). A 10 kW turbine there would make about 19,260 kWh a year, worth $2,721 at MT's 14.13¢/kWh. Against an installed cost of about $100,000, that is a payback of 37 years, and the turbine is built to last about 20.
What to do in Sweet Grass County
A home turbine is not worth buying for savings in Sweet Grass County unless your spot is far windier than the county average, 8.2 m/s at the hub against 5.94 m/s here. Per kW, solar panels would make about 1,203 kWh a year here against the turbine's 1,926, so get a solar quote first.
What would have to change
- Power would have to cost 26¢/kWh, 1.8 times what MT pays now.
- Or the average wind at the hub would have to be 8.2 m/s instead of 5.94. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of MT
Sweet Grass County is the 934th 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 Sweet Grass County
January is the strongest month here, at 7.94 m/s and about 2,839 kWh. July is the weakest, 4.20 m/s and 647 kWh, so the best month makes 4.4 times the worst. November to March brings in 61% of the year's output in Sweet Grass County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 7.94 m/s | 2,839 kWh | $401 |
| February | 6.93 m/s | 2,038 kWh | $288 |
| March | 6.45 m/s | 1,954 kWh | $276 |
| April | 5.66 m/s | 1,411 kWh | $199 |
| May | 5.02 m/s | 1,074 kWh | $152 |
| June | 4.84 m/s | 942 kWh | $133 |
| July | 4.20 m/s | 647 kWh | $91 |
| August | 4.25 m/s | 672 kWh | $95 |
| September | 5.00 m/s | 1,029 kWh | $145 |
| October | 6.25 m/s | 1,831 kWh | $259 |
| November | 7.30 m/s | 2,395 kWh | $338 |
| December | 7.49 m/s | 2,589 kWh | $366 |
What a taller tower would buy
Measured at 10 m the wind in Sweet Grass County averages 4.6 m/s; at 50 m it is 6.69 m/s. That gives a shear exponent of 0.233, typical of ordinary open country. Going from 20 m to 50 m takes output from 15,347 to 24,801 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 | 5.4 m/s | 15,347 kWh | 46 years |
| 30 m | 5.94 m/s | 19,255 kWh | 37 years |
| 40 m | 6.35 m/s | 22,307 kWh | 32 years |
| 50 m | 6.69 m/s | 24,801 kWh | 29 years |
Counties around Sweet Grass County
1 of the 6 closest counties is windier at turbine height; the windiest, Golden Valley County, averages 6 m/s.
- Stillwater County, MT: 5.8 m/s, 18,226 kWh, payback 39 years (29 mi)
- Park County, MT: 4.68 m/s, 10,445 kWh, payback 68 years (37 mi)
- Wheatland County, MT: 5.89 m/s, 18,890 kWh, payback 38 years (48 mi)
- Golden Valley County, MT: 6 m/s, 19,704 kWh, payback 36 years (54 mi)
- Carbon County, MT: 4.41 m/s, 8,807 kWh, payback 80 years (60 mi)
- Gallatin County, MT: 4.18 m/s, 7,515 kWh, payback 94 years (62 mi)
Sun versus wind in Sweet Grass County
Sweet Grass 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 1,926. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.6 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.