Wind Turbine Payback in Napa County, CA
Wind turbine payback in Napa 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 Napa County, CA averages 3.97 m/s (8.9 mph). A 10 kW turbine there would make about 6,428 kWh a year, worth $2,094 at CA's 32.58¢/kWh. Against an installed cost of about $100,000, that is a payback of 48 years, and the turbine is built to last about 20.
What to do in Napa County
A home turbine is not worth buying for savings in Napa County unless your spot is far windier than the county average, 5.4 m/s at the hub against 3.97 m/s here. Per kW, solar panels would make about 1,501 kWh a year here against the turbine's 643, so get a solar quote first.
What would have to change
- Power would have to cost 78¢/kWh, 2.4 times what CA pays now.
- Or the average wind at the hub would have to be 5.4 m/s instead of 3.97. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of CA
Napa County is the 2,080th 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 Napa County
December is the strongest month here, at 4.18 m/s and about 638 kWh. August is the weakest, 3.66 m/s and 424 kWh, so the best month makes 1.5 times the worst. November to March brings in 44% of the year's output in Napa County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 3.99 m/s | 553 kWh | $180 |
| February | 4.22 m/s | 591 kWh | $193 |
| March | 4.08 m/s | 595 kWh | $194 |
| April | 4.14 m/s | 598 kWh | $195 |
| May | 4.13 m/s | 614 kWh | $200 |
| June | 4.07 m/s | 568 kWh | $185 |
| July | 3.70 m/s | 440 kWh | $143 |
| August | 3.66 m/s | 424 kWh | $138 |
| September | 3.76 m/s | 445 kWh | $145 |
| October | 3.92 m/s | 527 kWh | $172 |
| November | 3.85 m/s | 482 kWh | $157 |
| December | 4.18 m/s | 638 kWh | $208 |
What a taller tower would buy
Measured at 10 m the wind in Napa County averages 3.03 m/s; at 50 m it is 4.5 m/s. That gives a shear exponent of 0.246, typical of ordinary open country. Going from 20 m to 50 m takes output from 4,702 to 9,339 kWh a year, 99% 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 | 3.59 m/s | 4,702 kWh | 65 years |
| 30 m | 3.97 m/s | 6,421 kWh | 48 years |
| 40 m | 4.26 m/s | 7,951 kWh | 39 years |
| 50 m | 4.5 m/s | 9,339 kWh | 33 years |
Counties around Napa County
5 of the 6 closest counties are windier at turbine height; the windiest, Contra Costa County, averages 4.85 m/s.
- Yolo County, CA: 4.42 m/s, 8,865 kWh, payback 35 years (26 mi)
- Solano County, CA: 4.42 m/s, 8,865 kWh, payback 35 years (27 mi)
- Sonoma County, CA: 4.66 m/s, 10,320 kWh, payback 30 years (32 mi)
- Marin County, CA: 4.37 m/s, 8,575 kWh, payback 36 years (39 mi)
- Contra Costa County, CA: 4.85 m/s, 11,537 kWh, payback 27 years (45 mi)
- Colusa County, CA: 3.92 m/s, 6,182 kWh, payback 50 years (47 mi)
Sun versus wind in Napa County
Napa 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 643. Kilowatt for kilowatt, panels make 2.3 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.