Wind Turbine Payback in St. Mary Parish, LA
Wind turbine payback in St. Mary Parish
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 Parish, LA averages 5.5 m/s (12.3 mph). A 10 kW turbine there would make about 16,037 kWh a year, worth $2,128 at LA's 13.27¢/kWh. Against an installed cost of about $100,000, that is a payback of 47 years, and the turbine is built to last about 20.
What to do in St. Mary Parish
A home turbine is not worth buying for savings in St. Mary Parish unless your spot is far windier than the county average, 8.6 m/s at the hub against 5.5 m/s here. Per kW, solar panels would make about 1,402 kWh a year here against the turbine's 1,604, so get a solar quote first.
What would have to change
- Power would have to cost 31¢/kWh, 2.3 times what LA pays now.
- Or the average wind at the hub would have to be 8.6 m/s instead of 5.5. A taller tower or an exposed ridge can add some of that; a rooftop never will.
Against the rest of LA
St. Mary Parish is the 1,222nd windiest of 3,144 US counties at turbine height; the national middle is 4.79 m/s. The windiest in LA is Iberia Parish at 5.86 m/s, payback 40 years.
Month by month in St. Mary Parish
January is the strongest month here, at 6.61 m/s and about 2,058 kWh. July is the weakest, 3.87 m/s and 504 kWh, so the best month makes 4.1 times the worst. November to March brings in 57% of the year's output in St. Mary Parish.
| Month | Wind at 30 m | Output | Worth |
|---|---|---|---|
| January | 6.61 m/s | 2,058 kWh | $273 |
| February | 6.61 m/s | 1,859 kWh | $247 |
| March | 6.33 m/s | 1,878 kWh | $249 |
| April | 6.33 m/s | 1,823 kWh | $242 |
| May | 5.34 m/s | 1,263 kWh | $168 |
| June | 4.40 m/s | 721 kWh | $96 |
| July | 3.87 m/s | 504 kWh | $67 |
| August | 3.91 m/s | 519 kWh | $69 |
| September | 4.76 m/s | 898 kWh | $119 |
| October | 5.49 m/s | 1,353 kWh | $180 |
| November | 6.03 m/s | 1,638 kWh | $217 |
| December | 6.51 m/s | 1,994 kWh | $265 |
What a taller tower would buy
Measured at 10 m the wind in St. Mary Parish averages 4.64 m/s; at 50 m it is 5.96 m/s. That gives a shear exponent of 0.156, typical of very open, smooth ground where height adds little. Going from 20 m to 50 m takes output from 13,671 to 19,408 kWh a year, 42% 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 | 5.17 m/s | 13,671 kWh | 55 years |
| 30 m | 5.5 m/s | 16,062 kWh | 47 years |
| 40 m | 5.76 m/s | 17,903 kWh | 42 years |
| 50 m | 5.96 m/s | 19,408 kWh | 39 years |
Counties around St. Mary Parish
1 of the 6 closest counties is windier at turbine height; the windiest, Iberia Parish, averages 5.86 m/s.
- Iberia Parish, LA: 5.86 m/s, 18,669 kWh, payback 40 years (23 mi)
- Assumption Parish, LA: 4.84 m/s, 11,472 kWh, payback 66 years (30 mi)
- St. Martin Parish, LA: 5.19 m/s, 13,837 kWh, payback 55 years (35 mi)
- Terrebonne Parish, LA: 5.23 m/s, 14,116 kWh, payback 53 years (43 mi)
- Iberville Parish, LA: 4.13 m/s, 7,248 kWh, payback over 100 years (45 mi)
- St. James Parish, LA: 4.7 m/s, 10,571 kWh, payback 71 years (49 mi)
Sun versus wind in St. Mary Parish
St. Mary Parish gets 4.8 kWh of sunshine per square metre a day on average. One kW of solar panels here would make roughly 1,402 kWh a year; one kW of the turbine above makes 1,604. 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.