← Field Notes Power & Generation No. 30

Small wind: the honest numbers

The cube rule explains all the disappointment.

Wind looks perfect on paper: it blows hardest in exactly the weather that flattens solar, and it works at night. The reality is harsher than the product page.

That single fact means a turbine advertised as "400W" is rated at a wind speed most sites rarely see. At half that speed it produces about 50W. And most small turbines have a cut-in speed of roughly 6–9 mph — below that they generate literally nothing while still looking productive on the mount.

What actually determines success:

Height beats hardware. Wind speed increases substantially with height above ground clutter. A turbine on a short pole beside a trailer sits in slow, turbulent air. Real installations use real towers.

Turbulence destroys output and bearings. Air tumbling over trees, buildings, or your own rig is worse than no wind.

You need a diversion load. Unlike solar, you can't simply disconnect a turbine when the bank is full — many designs freewheel and destroy themselves with no load. A diversion controller dumps excess into a resistive load. Not optional.

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