We have a 16 x 30 AGP with a 1.5 two-speed pump and a 19" sand filter. The pump runs on low speed 6 hours during the night and on high only when I vacuum. Our system is in it's 6th summer now on the same sand. Energy consumption on low speed is 1/4 of high speed. We get a 45% cost break during off-peak hours here and I have not noticed any appreciable increase in the electric bill during pool season. I'm a fan of two-speed pumps.