Wind Turbine Payback in Granite County, MT
Wind turbine payback in Granite 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 Granite County, MT averages 3.77 m/s (8.4 mph). A 10 kW turbine there would make about 5,477 kWh a year, worth $774 at MT's 14.13¢/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 Granite County
A home turbine is not worth buying for savings in Granite County unless your spot is far windier than the county average, 8.2 m/s at the hub against 3.77 m/s here. Per kW, solar panels would make about 1,171 kWh a year here against the turbine's 548, so get a solar quote first.
What would have to change
- Power would have to cost 91¢/kWh, 6.5 times what MT pays now.
- Or the average wind at the hub would have to be 8.2 m/s instead of 3.77. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of MT
Granite County is the 2,225th 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 Granite County
January is the strongest month here, at 4.42 m/s and about 753 kWh. August is the weakest, 3.10 m/s and 246 kWh, so the best month makes 3.1 times the worst. November to March brings in 57% of the year's output in Granite County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 4.42 m/s | 753 kWh | $106 |
| February | 4.13 m/s | 555 kWh | $78 |
| March | 4.15 m/s | 626 kWh | $88 |
| April | 3.82 m/s | 468 kWh | $66 |
| May | 3.36 m/s | 323 kWh | $46 |
| June | 3.31 m/s | 295 kWh | $42 |
| July | 3.13 m/s | 255 kWh | $36 |
| August | 3.10 m/s | 246 kWh | $35 |
| September | 3.41 m/s | 328 kWh | $46 |
| October | 3.93 m/s | 531 kWh | $75 |
| November | 4.21 m/s | 632 kWh | $89 |
| December | 4.23 m/s | 660 kWh | $93 |
What a taller tower would buy
Measured at 10 m the wind in Granite County averages 2.58 m/s; at 50 m it is 4.49 m/s. That gives a shear exponent of 0.344, typical of rough, sheltered ground: trees or buildings slow the low wind a lot. Going from 20 m to 50 m takes output from 3,492 to 9,279 kWh a year, 166% 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 | 3.28 m/s | 3,492 kWh | over 100 years |
| 30 m | 3.77 m/s | 5,461 kWh | over 100 years |
| 40 m | 4.16 m/s | 7,398 kWh | 96 years |
| 50 m | 4.49 m/s | 9,279 kWh | 76 years |
Counties around Granite County
2 of the 6 closest counties are windier at turbine height; the windiest, Jefferson County, averages 4.03 m/s.
- Deer Lodge County, MT: 3.65 m/s, 4,948 kWh, payback over 100 years (25 mi)
- Powell County, MT: 3.35 m/s, 3,757 kWh, payback over 100 years (39 mi)
- Ravalli County, MT: 2.71 m/s, 1,821 kWh, payback over 100 years (39 mi)
- Missoula County, MT: 2.8 m/s, 2,047 kWh, payback over 100 years (49 mi)
- Silver Bow County, MT: 3.78 m/s, 5,523 kWh, payback over 100 years (50 mi)
- Jefferson County, MT: 4.03 m/s, 6,729 kWh, payback over 100 years (68 mi)
Sun versus wind in Granite County
Granite County gets 4.01 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,171 kWh a year; one kW of the turbine above makes 548. Kilowatt for kilowatt, panels make 2.1 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.