Board Thread:General Discussion/@comment-24860474-20140424212800

So I've found that even with sufficient elevation and removing obstructions, the output of a Wind Mill can dip low enough that it looks like it isn't working (no filling on the Turbine icon) but actually it's a little above 0.2EU/t.

I would speculate (but of course I could be wrong) that there's some sort of 'wind speed' variable that is factored into the equation. 