Wind Turbine Payback in Darlington County, SC
Wind turbine payback in Darlington 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 Darlington County, SC averages 4.46 m/s (10 mph). A 10 kW turbine there would make about 9,100 kWh a year, worth $1,447 at SC's 15.9¢/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 Darlington County
A home turbine is not worth buying for savings in Darlington County unless your spot is far windier than the county average, 7.6 m/s at the hub against 4.46 m/s here. Per kW, solar panels would make about 1,329 kWh a year here against the turbine's 910, so get a solar quote first.
What would have to change
- Power would have to cost 55¢/kWh, 3.5 times what SC pays now.
- Or the average wind at the hub would have to be 7.6 m/s instead of 4.46. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of SC
Darlington County is the 1,772nd windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. The windiest in SC is Beaufort County at 5.71 m/s, payback 36 years.
Month by month in Darlington County
April is the strongest month here, at 5.25 m/s and about 1,170 kWh. August is the weakest, 3.52 m/s and 376 kWh, so the best month makes 3.1 times the worst. November to March brings in 50% of the year's output in Darlington County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 4.82 m/s | 961 kWh | $153 |
| February | 5.00 m/s | 964 kWh | $153 |
| March | 5.14 m/s | 1,147 kWh | $182 |
| April | 5.25 m/s | 1,170 kWh | $186 |
| May | 4.52 m/s | 805 kWh | $128 |
| June | 3.89 m/s | 494 kWh | $79 |
| July | 3.69 m/s | 434 kWh | $69 |
| August | 3.52 m/s | 376 kWh | $60 |
| September | 4.20 m/s | 628 kWh | $100 |
| October | 4.40 m/s | 744 kWh | $118 |
| November | 4.57 m/s | 800 kWh | $127 |
| December | 4.59 m/s | 840 kWh | $134 |
What a taller tower would buy
Measured at 10 m the wind in Darlington County averages 3.24 m/s; at 50 m it is 5.18 m/s. That gives a shear exponent of 0.292, typical of ordinary open country. Going from 20 m to 50 m takes output from 6,398 to 13,768 kWh a year, 115% 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 | 3.96 m/s | 6,398 kWh | 98 years |
| 30 m | 4.46 m/s | 9,114 kWh | 69 years |
| 40 m | 4.85 m/s | 11,558 kWh | 54 years |
| 50 m | 5.18 m/s | 13,768 kWh | 46 years |
Counties around Darlington County
4 of the 6 closest counties are windier at turbine height; the windiest, Marlboro County, averages 5 m/s.
- Lee County, SC: 4.98 m/s, 12,400 kWh, payback 51 years (20 mi)
- Chesterfield County, SC: 4.46 m/s, 9,100 kWh, payback 69 years (24 mi)
- Marlboro County, SC: 5 m/s, 12,535 kWh, payback 50 years (25 mi)
- Florence County, SC: 4.98 m/s, 12,400 kWh, payback 51 years (25 mi)
- Dillon County, SC: 5 m/s, 12,535 kWh, payback 50 years (34 mi)
- Kershaw County, SC: 3.44 m/s, 4,094 kWh, payback over 100 years (36 mi)
Sun versus wind in Darlington County
Darlington County gets 4.55 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,329 kWh a year; one kW of the turbine above makes 910. 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.