2-Speed Pool Pumps runs on two speeds: High speed (3450 RPM) and Low speed (1725 RPM). Two speed pool pumps runs more efficiently compared with the single speed which always runs at high speed. It also at very low noise during low speed operation. You can run the pump at Low speed setting 24/7 allowing you to save money.
You will want to set the pump at high speed:
In and above ground 2 speed pool pumps are more expensive than then single speed pump variation, but you'll get an average savings of 50%-70% on energy cost. The savings is definitely worth the extra money to spend in buying it.