Wind Turbine Payback in Knox County, ME
Wind turbine payback in Knox County
Only just. The money comes back late in the turbine's life.
At 30 m, the height a home turbine tower usually reaches, the wind in Knox County, ME averages 6.26 m/s (14 mph). A 10 kW turbine there would make about 21,632 kWh a year, worth $6,539 at ME's 30.23¢/kWh. Against an installed cost of about $100,000, that is a payback of 15 years, and the turbine is built to last about 20.
What to do in Knox County
It is close enough that your own site decides it. If you have open land with no trees or buildings upwind, ask an installer to log the wind at 30 m or higher; anything above 5.6 m/s pays back in time. Per kW, solar panels would make about 1,080 kWh a year here against the turbine's 2,163, so get a solar quote first.
What would have to change
- Power already costs enough here: break-even is 23¢/kWh and ME pays 30.23¢.
- The wind clears the break-even speed of 5.6 m/s at today's price.
Against the rest of ME
Knox County is the 520th windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. It is the windiest county in ME.
Month by month in Knox County
January is the strongest month here, at 7.54 m/s and about 2,615 kWh. August is the weakest, 4.80 m/s and 953 kWh, so the best month makes 2.7 times the worst. November to March brings in 56% of the year's output in Knox County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 7.54 m/s | 2,615 kWh | $791 |
| February | 7.55 m/s | 2,367 kWh | $716 |
| March | 7.23 m/s | 2,437 kWh | $737 |
| April | 6.34 m/s | 1,827 kWh | $552 |
| May | 5.51 m/s | 1,369 kWh | $414 |
| June | 5.14 m/s | 1,110 kWh | $336 |
| July | 4.83 m/s | 968 kWh | $293 |
| August | 4.80 m/s | 953 kWh | $288 |
| September | 5.37 m/s | 1,243 kWh | $376 |
| October | 6.43 m/s | 1,946 kWh | $588 |
| November | 6.99 m/s | 2,214 kWh | $669 |
| December | 7.45 m/s | 2,562 kWh | $774 |
What a taller tower would buy
Measured at 10 m the wind in Knox County averages 5.25 m/s; at 50 m it is 6.79 m/s. That gives a shear exponent of 0.160, typical of very open, smooth ground where height adds little. Going from 20 m to 50 m takes output from 18,699 to 25,529 kWh a year, 37% more, before counting the extra cost of the taller tower.
| Hub height | Average wind | Output | Payback |
|---|---|---|---|
| 20 m | 5.86 m/s | 18,699 kWh | 18 years |
| 30 m | 6.26 m/s | 21,611 kWh | 15 years |
| 40 m | 6.55 m/s | 23,789 kWh | 14 years |
| 50 m | 6.79 m/s | 25,529 kWh | 13 years |
Counties around Knox County
None of the 6 closest counties is windier than Knox County.
- Lincoln County, ME: 4.86 m/s, 11,603 kWh, payback 29 years (24 mi)
- Waldo County, ME: 3.48 m/s, 4,250 kWh, payback 78 years (30 mi)
- Sagadahoc County, ME: 3.65 m/s, 4,948 kWh, payback 67 years (41 mi)
- Kennebec County, ME: 3.51 m/s, 4,368 kWh, payback 76 years (44 mi)
- Hancock County, ME: 4.76 m/s, 10,954 kWh, payback 30 years (49 mi)
- Androscoggin County, ME: 3.65 m/s, 4,948 kWh, payback 67 years (59 mi)
Sun versus wind in Knox County
Knox County gets 3.7 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,080 kWh a year; one kW of the turbine above makes 2,163. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 2.0 times. Panel output assumes an 80% system performance ratio.
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.