Wind Turbine Payback in St. Mary's County, MD
Wind turbine payback in St. Mary's 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. Mary's County, MD averages 5.43 m/s (12.1 mph). A 10 kW turbine there would make about 15,534 kWh a year, worth $3,310 at MD's 21.31¢/kWh. Against an installed cost of about $100,000, that is a payback of 30 years, and the turbine is built to last about 20.
What to do in St. Mary's County
A home turbine is not worth buying for savings in St. Mary's County unless your spot is far windier than the county average, 6.5 m/s at the hub against 5.43 m/s here. Per kW, solar panels would make about 1,238 kWh a year here against the turbine's 1,553, so get a solar quote first.
What would have to change
- Power would have to cost 32¢/kWh, 1.5 times what MD pays now.
- Or the average wind at the hub would have to be 6.5 m/s instead of 5.43. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of MD
St. Mary's County is the 1,252nd windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. The windiest in MD is Worcester County at 7.01 m/s, payback 17 years.
Month by month in St. Mary's County
January is the strongest month here, at 6.26 m/s and about 1,837 kWh. August is the weakest, 4.18 m/s and 639 kWh, so the best month makes 2.9 times the worst. November to March brings in 54% of the year's output in St. Mary's County.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.26 m/s | 1,837 kWh | $391 |
| February | 6.23 m/s | 1,644 kWh | $350 |
| March | 6.24 m/s | 1,826 kWh | $389 |
| April | 6.12 m/s | 1,695 kWh | $361 |
| May | 5.20 m/s | 1,183 kWh | $252 |
| June | 4.66 m/s | 846 kWh | $180 |
| July | 4.25 m/s | 669 kWh | $143 |
| August | 4.18 m/s | 639 kWh | $136 |
| September | 4.87 m/s | 957 kWh | $204 |
| October | 5.48 m/s | 1,348 kWh | $287 |
| November | 5.83 m/s | 1,517 kWh | $323 |
| December | 5.95 m/s | 1,642 kWh | $350 |
What a taller tower would buy
Measured at 10 m the wind in St. Mary's County averages 4.45 m/s; at 50 m it is 5.96 m/s. That gives a shear exponent of 0.182, typical of ordinary open country. Going from 20 m to 50 m takes output from 12,836 to 19,408 kWh a year, 51% 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 | 5.04 m/s | 12,836 kWh | 37 years |
| 30 m | 5.43 m/s | 15,540 kWh | 30 years |
| 40 m | 5.72 m/s | 17,659 kWh | 27 years |
| 50 m | 5.96 m/s | 19,408 kWh | 24 years |
Counties around St. Mary's County
None of the 6 closest counties is windier than St. Mary's County.
- Westmoreland County, VA: 3.63 m/s, 4,862 kWh, payback over 100 years (17 mi)
- Calvert County, MD: 5.21 m/s, 13,976 kWh, payback 34 years (21 mi)
- Richmond County, VA: 3.63 m/s, 4,862 kWh, payback over 100 years (22 mi)
- Northumberland County, VA: 5.43 m/s, 15,534 kWh, payback 38 years (27 mi)
- Essex County, VA: 3.63 m/s, 4,862 kWh, payback over 100 years (29 mi)
- Dorchester County, MD: 5.21 m/s, 13,976 kWh, payback 34 years (30 mi)
Sun versus wind in St. Mary's County
St. Mary's County gets 4.24 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,238 kWh a year; one kW of the turbine above makes 1,553. This is one of the rare places where a kilowatt of turbine out-produces a kilowatt of panels, by 1.3 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.