Rheem’s Prestige series condensing tankless water heater harnesses condensing technology to achieve a 0.94 EF. It is the company’s most efficient tankless water heater to date, and is Energy Star qualified. The unit comes installed with intelligent electronic controls and a self-diagnosis system. Employing a minimum flow rate of 0.26 gpm, and a minimum activation flow rate of 0.40 gpm, homeowners using low-flow fixtures receive hot water without having to increase the flow. Units are available in outdoor and indoor models, the latter of which can vent with PVC piping.