What's the most energy-efficient way to run a pool pump?

Run the pump at the lowest speed that still does the job, and set the timer for the minimum runtime needed to keep the water clean. Power consumption drops with the cube of speed — cutting speed in half uses roughly one-eighth the power. For a typical pool, aim for one water turnover per day, which at low speed might take 8–12 hours. Start with 8 hours at 1200 rpm, then adjust down based on water clarity.