MasterTemp heaters are well-known for best-in-class energy efficiency and low emissions, even while heating your pool quickly. They feature an exceptionally compact design for such a high-performance heater, so they fit on smaller, less-intrusive equipment pads. Controls are intuitive and easy to use. MasterTemp heaters are also designed for super-quiet operation to help keep your poolside experience tranquil. On an medium sized inground pool, this heater will bring up your pool temperature just under 2 degrees fahrenheit per hour. 

Pentair Mastertemp 400,000 BTU NatGas Heater