I have a 2 speed 1hp Hayward Super Pump and the low/high speed switch is on the back of the pump.

You can save electricity (and extend the lifespan of your pump) by running it 8-10 hours per day instead of 24. As I understand it pumps should be sized to turn the water over in that time period.

When running on low speed it will take twice as long to turn the water. So while the power consumption is 1/4 to 1/3 that of high speed, it'll run twice as long making the actual cost 1/2 to 2/3 the operating cost of a high speed.