How the County Numbers Are Made
The wind
Every county uses NASA's POWER climate record, the 2001 to 2025 average wind at 10 m and 50 m above ground at the county's centre. Those two heights give each county its own wind shear, how fast the wind picks up with height, which carries the 50 m reading down to the 30 m tower the model assumes. The middle county's shear exponent is 0.253. An average speed hides the gusts and lulls that actually turn a rotor, so the model spreads it into hours with a Rayleigh distribution, the standard default when only the mean is known.
The turbine
A generic 10 kW machine with a 7 m rotor, the size a rural home on an acre or more usually installs. It starts turning at 3 m/s, reaches full output at 11 m/s and shuts down above 25 m/s. 10% is taken off for downtime, wiring and inverter losses. It is not any one maker's power curve, so a specific model can do somewhat better or worse.
The money
Each kWh the turbine makes is valued at the state's average residential price from the EIA, on the assumption that it replaces power you would otherwise buy. Installed cost is $10,000 per kW, $100,000 for the whole system on its tower, with no tax credit. Payback is that cost divided by a year's savings, and it is judged against a 20-year working life. Maintenance is not added, which flatters the turbine slightly.
Where a county figure is weakest
One reading at a county's centre on a roughly 50 km grid cannot see a ridge, a valley or a line of trees, and those decide a real turbine's output. Prices are state averages, so a co-op with cheap power or a utility with expensive power can move the answer a long way. And the installed cost is a planning figure; real quotes vary with the tower, the soil and the distance to your meter. That is why every county page ends with what would have to change and what to check before buying.
Three counties to see it at work
Emanuel County, GA sits at the national middle for wind. Aleutians West Census Area, AK has the strongest wind at turbine height, and Honolulu County, HI the quickest payback. The effect of height is worked through in why tower height decides it, and the effect of price in what power price makes it pay.