Wind Turbine Payback in St. Johns County, FL
Wind turbine payback in St. Johns 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 St. Johns County, FL averages 4.52 m/s (10.1 mph). A 10 kW turbine there would make about 9,459 kWh a year, worth $1,449 at FL's 15.32¢/kWh. Against an installed cost of about $100,000, that is a payback of 69 years, and the turbine is built to last about 20.
What to do in St. Johns County
A home turbine is not worth buying for savings in St. Johns County unless your spot is far windier than the county average, 7.8 m/s at the hub against 4.52 m/s here. Per kW, solar panels would make about 1,393 kWh a year here against the turbine's 946, so get a solar quote first.
What would have to change
- Power would have to cost 53¢/kWh, 3.5 times what FL pays now.
- Or the average wind at the hub would have to be 7.8 m/s instead of 4.52. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of FL
St. Johns County is the 1,739th windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. The windiest in FL is Brevard County at 5.62 m/s, payback 39 years.
Month by month in St. Johns County
January is the strongest month here, at 5.08 m/s and about 1,112 kWh. July is the weakest, 3.55 m/s and 386 kWh, so the best month makes 2.9 times the worst. November to March brings in 52% of the year's output in St. Johns County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 5.08 m/s | 1,112 kWh | $170 |
| February | 4.93 m/s | 925 kWh | $142 |
| March | 4.94 m/s | 1,029 kWh | $158 |
| April | 4.81 m/s | 927 kWh | $142 |
| May | 4.40 m/s | 745 kWh | $114 |
| June | 3.81 m/s | 464 kWh | $71 |
| July | 3.55 m/s | 386 kWh | $59 |
| August | 3.64 m/s | 415 kWh | $64 |
| September | 4.50 m/s | 769 kWh | $118 |
| October | 4.74 m/s | 919 kWh | $141 |
| November | 4.96 m/s | 1,006 kWh | $154 |
| December | 4.90 m/s | 1,008 kWh | $154 |
What a taller tower would buy
Measured at 10 m the wind in St. Johns County averages 3.64 m/s; at 50 m it is 5 m/s. That gives a shear exponent of 0.197, typical of ordinary open country. Going from 20 m to 50 m takes output from 7,484 to 12,535 kWh a year, 67% 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 | 4.17 m/s | 7,484 kWh | 87 years |
| 30 m | 4.52 m/s | 9,467 kWh | 69 years |
| 40 m | 4.78 m/s | 11,114 kWh | 59 years |
| 50 m | 5 m/s | 12,535 kWh | 52 years |
Counties around St. Johns County
None of the 6 closest counties is windier than St. Johns County.
- Putnam County, FL: 3.78 m/s, 5,523 kWh, payback over 100 years (29 mi)
- Clay County, FL: 3.85 m/s, 5,847 kWh, payback over 100 years (29 mi)
- Flagler County, FL: 4.01 m/s, 6,628 kWh, payback 99 years (30 mi)
- Duval County, FL: 3.42 m/s, 4,018 kWh, payback over 100 years (34 mi)
- Bradford County, FL: 3.85 m/s, 5,847 kWh, payback over 100 years (46 mi)
- Nassau County, FL: 3.42 m/s, 4,018 kWh, payback over 100 years (54 mi)
Sun versus wind in St. Johns County
St. Johns County gets 4.77 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,393 kWh a year; one kW of the turbine above makes 946. Kilowatt for kilowatt, panels make 1.5 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.