Wind Turbine Payback in Marin County, CA
Wind turbine payback in Marin 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 Marin County, CA averages 4.37 m/s (9.8 mph). A 10 kW turbine there would make about 8,575 kWh a year, worth $2,794 at CA's 32.58¢/kWh. Against an installed cost of about $100,000, that is a payback of 36 years, and the turbine is built to last about 20.
What to do in Marin County
A home turbine is not worth buying for savings in Marin County unless your spot is far windier than the county average, 5.4 m/s at the hub against 4.37 m/s here. Per kW, solar panels would make about 1,501 kWh a year here against the turbine's 858, so get a solar quote first.
What would have to change
- Power would have to cost 58¢/kWh, 1.8 times what CA pays now.
- Or the average wind at the hub would have to be 5.4 m/s instead of 4.37. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of CA
Marin County is the 1,849th windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. The windiest in CA is San Francisco County at 6.53 m/s, payback 13 years.
Month by month in Marin County
May is the strongest month here, at 4.82 m/s and about 964 kWh. November is the weakest, 3.94 m/s and 515 kWh, so the best month makes 1.9 times the worst. November to March brings in 40% of the year's output in Marin County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 4.20 m/s | 647 kWh | $211 |
| February | 4.51 m/s | 719 kWh | $234 |
| March | 4.48 m/s | 782 kWh | $255 |
| April | 4.69 m/s | 866 kWh | $282 |
| May | 4.82 m/s | 964 kWh | $314 |
| June | 4.80 m/s | 923 kWh | $301 |
| July | 4.37 m/s | 728 kWh | $237 |
| August | 4.23 m/s | 664 kWh | $216 |
| September | 4.05 m/s | 563 kWh | $183 |
| October | 3.94 m/s | 532 kWh | $173 |
| November | 3.94 m/s | 515 kWh | $168 |
| December | 4.43 m/s | 759 kWh | $247 |
What a taller tower would buy
Measured at 10 m the wind in Marin County averages 3.49 m/s; at 50 m it is 4.85 m/s. That gives a shear exponent of 0.204, typical of ordinary open country. Going from 20 m to 50 m takes output from 6,694 to 11,537 kWh a year, 72% 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 | 4.02 m/s | 6,694 kWh | 46 years |
| 30 m | 4.37 m/s | 8,575 kWh | 36 years |
| 40 m | 4.63 m/s | 10,158 kWh | 30 years |
| 50 m | 4.85 m/s | 11,537 kWh | 27 years |
Counties around Marin County
5 of the 6 closest counties are windier at turbine height; the windiest, San Francisco County, averages 6.53 m/s.
- San Francisco County, CA: 6.53 m/s, 23,628 kWh, payback 13 years (27 mi)
- Sonoma County, CA: 4.66 m/s, 10,320 kWh, payback 30 years (34 mi)
- Napa County, CA: 3.97 m/s, 6,428 kWh, payback 48 years (39 mi)
- Contra Costa County, CA: 4.85 m/s, 11,537 kWh, payback 27 years (44 mi)
- Solano County, CA: 4.42 m/s, 8,865 kWh, payback 35 years (46 mi)
- San Mateo County, CA: 5.02 m/s, 12,670 kWh, payback 24 years (49 mi)
Sun versus wind in Marin County
Marin County gets 5.14 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,501 kWh a year; one kW of the turbine above makes 858. 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.