Wind Turbine Payback in Johnston County, NC
Wind turbine payback in Johnston 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 Johnston County, NC averages 5.2 m/s (11.6 mph). A 10 kW turbine there would make about 13,907 kWh a year, worth $2,078 at NC's 14.94¢/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 Johnston County
A home turbine is not worth buying for savings in Johnston County unless your spot is far windier than the county average, 7.9 m/s at the hub against 5.2 m/s here. Per kW, solar panels would make about 1,305 kWh a year here against the turbine's 1,391, so get a solar quote first.
What would have to change
- Power would have to cost 36¢/kWh, 2.4 times what NC pays now.
- Or the average wind at the hub would have to be 7.9 m/s instead of 5.2. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of NC
Johnston County is the 1,379th windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. The windiest in NC is Dare County at 6.91 m/s, payback 25 years.
Month by month in Johnston County
March is the strongest month here, at 5.99 m/s and about 1,665 kWh. August is the weakest, 4.04 m/s and 577 kWh, so the best month makes 2.9 times the worst. November to March brings in 51% of the year's output in Johnston County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 5.67 m/s | 1,468 kWh | $219 |
| February | 5.88 m/s | 1,444 kWh | $216 |
| March | 5.99 m/s | 1,665 kWh | $249 |
| April | 6.06 m/s | 1,659 kWh | $248 |
| May | 5.23 m/s | 1,201 kWh | $179 |
| June | 4.55 m/s | 793 kWh | $118 |
| July | 4.31 m/s | 701 kWh | $105 |
| August | 4.04 m/s | 577 kWh | $86 |
| September | 4.81 m/s | 929 kWh | $139 |
| October | 5.09 m/s | 1,119 kWh | $167 |
| November | 5.37 m/s | 1,244 kWh | $186 |
| December | 5.42 m/s | 1,312 kWh | $196 |
What a taller tower would buy
Measured at 10 m the wind in Johnston County averages 3.9 m/s; at 50 m it is 5.94 m/s. That gives a shear exponent of 0.261, typical of ordinary open country. Going from 20 m to 50 m takes output from 10,423 to 19,260 kWh a year, 85% 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 | 4.68 m/s | 10,423 kWh | 64 years |
| 30 m | 5.2 m/s | 13,897 kWh | 48 years |
| 40 m | 5.6 m/s | 16,790 kWh | 40 years |
| 50 m | 5.94 m/s | 19,260 kWh | 35 years |
Counties around Johnston County
None of the 6 closest counties is windier than Johnston County.
- Wayne County, NC: 5.2 m/s, 13,907 kWh, payback 48 years (23 mi)
- Wake County, NC: 3.47 m/s, 4,211 kWh, payback over 100 years (25 mi)
- Wilson County, NC: 5.2 m/s, 13,907 kWh, payback 48 years (28 mi)
- Harnett County, NC: 4.39 m/s, 8,690 kWh, payback 77 years (30 mi)
- Sampson County, NC: 4.9 m/s, 11,866 kWh, payback 56 years (36 mi)
- Nash County, NC: 4.35 m/s, 8,460 kWh, payback 79 years (38 mi)
Sun versus wind in Johnston County
Johnston County gets 4.47 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,305 kWh a year; one kW of the turbine above makes 1,391. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.1 times. 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.