ENERGY STAR certified with a UEF of 0.95;Flexibility in Installation-PVC venting flexibility (2” up to 50’ & 3" up to 150’);Install indoor or outdoor (outdoor kit sold separately);Save up to $116/year on operating costs-Compared to a standard 50-gallon atmospheric vent natural gas tank water heater;Lasts 3x Longer-Integrated X3 Scale Prevention Technology provides protection for the heat exchanger;Expandable for Larger Applications-Cascade up to 12 like heaters when multiple water heaters are required to work in conjunction (cable included);Built-in Control Display-Check status, error codes and settings