Single speed pumps are more efficient in terms of service factor and windings. 2nd speed is kind of an additional thought in their design, thus the windings are less than optimal. However the savings is in resistance to flow and head pressure. 2 speed give us the option of a high speed for running things like spa jets and pool cleaners vs just under sizing the equipment. The ao smith centurion 2 speed series has better service factor on their low speed vs traditional 2 speed. Running a larger filter can dramaticly reduce head pressure. I started with a 84 sqin hayward cartridge with 10-20 psi head. I swapped over to a clearways 320 sqin cartridge and run 3 psi on less than clean filters. The main difference is the jets are twice as powerful and the skimmers have eddys in them while the suction cleaner still has enough gusto to scoot around all for 3/4 hp.
I actually did an energy audit last week, our houses were quite similar in size, pools the same size. his pump 1 1/2 hp timed 10 hrs a day, his hvacs were twice the size of mine and dirty. House was modern construction, decent windows and insulation, his electric bill was $900 last month! For so many people it takes a giant bill to consider if they might be wasting power.
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