Small wind turbines for off-grid: worth it, or not?

What it really makes

Turbine labels list power at a strong, steady wind most places rarely see. Real numbers are smaller.

In the Warwick Wind Trials, 26 rooftop turbines were measured for a year. On average they ran at 0.85% of their rated output (4.15% counting only the time they were working) and made about 214 Wh a day. That charges phones and runs a few LED lights. It won't keep a fridge going, which takes 1 to 2 kWh a day.

When it can work

The DOE's rules for a turbine worth having:

• Average wind of at least 9 mph over the year, at the turbine's height, for an off-grid wind and solar system.
• A tower, not a roof. The bottom of the blades at least 30 feet above anything within 300 feet: trees, barns, the house. The DOE doesn't recommend rooftops at all: vibration, noise, structural problems and turbulent air that wears the turbine out.
• Somewhere it can run. Towers need room, a foundation, and often a permit.

Meet all three and wind fills a real gap. Across much of the US, the DOE notes, wind is strongest in winter, when there's the least sun. A turbine plus solar panels covers more of the year than either alone, and the battery bank fills in when both are quiet.

Fail any of them

Put the money into solar panels. They have no moving parts, last decades and make their rated power whenever the sun is strong. Size them for your darkest month and the winter problem is solved without a tower: see what yours needs.