Does a steeper blade angle make a windmill produce more electricity? Most people guess 45 degrees is ideal. The real answer may be different. You build a small windmill from construction toys and attach it to an electric generator. You cut blades in four sizes from venetian blind slats. A fan blows air at the windmill from one meter away. You set the blades at angles from 0 to 90 degrees and read the current output on an ammeter. The highest current came at 75 degrees for every blade size that spun. At 90 degrees the blades sat flat against the wind and produced nothing. The 300 cm² blades beat the larger 400 cm² set. The bigger blades were too wide for the windmill frame.