Windmills are generally rated to the power they would produce in ideal conditions. After that, a brake stops the windmill’s rotation. Of course, too much wind could damage the turbine, so windmills have a cut-out speed, too. The turbine then reaches its maximum rated wind speed, above which the power output holds steady under ideal conditions, generally 22 to 36 miles per hour, depending on the type of windmill. Power output continues to grow as the wind speed increases, but at a slower rate than it does right after the cut-in point. The turbine starts to create power at what is known as the cut-in speed. If there is too little wind and the blades are moving too slowly, the wind turbine no longer produces electricity. But if the wind speed doubles, then a windmill could produce eight times more power under the appropriate conditions. The short answer is that if they move slowly, they produce less power.
