TURBRO Swimming Pool Heat Pump - 20,000 BTU - for Above and In Ground Pools and Spas - High Efficiency, All Electric Heater - No Natural Gas or Propane Needed, Manatee M20. Extends your swimming season, allowing you to enjoy swimming even in cool spring and autumn months. Make the most of your pool with our efficient pool heat pump. Versatile and suitable for a variety of pools, including in-ground, above-ground, and inflatable options. Enjoy the flexibility and comfort it brings.[Tips for Optimal Use]: Works best in outdoor temperatures of 60°F or above. Efficiency varies based on pool size and weather conditions. Use a pool cover in cooler temperatures to reduce heat loss and speed up heating.