Wind Turbine Payback in Contra Costa County, CA
Wind turbine payback in Contra Costa 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 Contra Costa County, CA averages 4.85 m/s (10.8 mph). A 10 kW turbine there would make about 11,537 kWh a year, worth $3,759 at CA's 32.58¢/kWh. Against an installed cost of about $100,000, that is a payback of 27 years, and the turbine is built to last about 20.
What to do in Contra Costa County
A home turbine is not worth buying for savings in Contra Costa County unless your spot is far windier than the county average, 5.4 m/s at the hub against 4.85 m/s here. Per kW, solar panels would make about 1,553 kWh a year here against the turbine's 1,154, so get a solar quote first.
What would have to change
- Power would have to cost 43¢/kWh, 1.3 times what CA pays now.
- Or the average wind at the hub would have to be 5.4 m/s instead of 4.85. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of CA
Contra Costa County is the 1,529th 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 Contra Costa County
July is the strongest month here, at 5.72 m/s and about 1,497 kWh. November is the weakest, 3.94 m/s and 514 kWh, so the best month makes 2.9 times the worst. November to March brings in 28% of the year's output in Contra Costa County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 3.91 m/s | 520 kWh | $169 |
| February | 4.46 m/s | 698 kWh | $227 |
| March | 4.64 m/s | 867 kWh | $282 |
| April | 5.13 m/s | 1,103 kWh | $359 |
| May | 5.56 m/s | 1,396 kWh | $455 |
| June | 5.75 m/s | 1,465 kWh | $477 |
| July | 5.72 m/s | 1,497 kWh | $488 |
| August | 5.44 m/s | 1,324 kWh | $431 |
| September | 4.98 m/s | 1,017 kWh | $331 |
| October | 4.49 m/s | 787 kWh | $256 |
| November | 3.94 m/s | 514 kWh | $167 |
| December | 4.23 m/s | 663 kWh | $216 |
What a taller tower would buy
Measured at 10 m the wind in Contra Costa County averages 3.91 m/s; at 50 m it is 5.36 m/s. That gives a shear exponent of 0.196, typical of ordinary open country. Going from 20 m to 50 m takes output from 9,213 to 15,034 kWh a year, 63% 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 | 4.48 m/s | 9,213 kWh | 33 years |
| 30 m | 4.85 m/s | 11,533 kWh | 27 years |
| 40 m | 5.13 m/s | 13,426 kWh | 23 years |
| 50 m | 5.36 m/s | 15,034 kWh | 20 years |
Counties around Contra Costa County
1 of the 6 closest counties is windier at turbine height; the windiest, San Mateo County, averages 5.02 m/s.
- Alameda County, CA: 4.17 m/s, 7,461 kWh, payback 41 years (19 mi)
- Solano County, CA: 4.42 m/s, 8,865 kWh, payback 35 years (24 mi)
- San Joaquin County, CA: 4.09 m/s, 7,038 kWh, payback 44 years (37 mi)
- San Mateo County, CA: 5.02 m/s, 12,670 kWh, payback 24 years (42 mi)
- Marin County, CA: 4.37 m/s, 8,575 kWh, payback 36 years (44 mi)
- Napa County, CA: 3.97 m/s, 6,428 kWh, payback 48 years (45 mi)
Sun versus wind in Contra Costa County
Contra Costa County gets 5.32 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,553 kWh a year; one kW of the turbine above makes 1,154. Kilowatt for kilowatt, panels make 1.3 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.