Energy Star certified with a UEF of 0.95;Easily maintain like-new performance by adding add X3 Scale Prevention at any time with an optional bypass cartridge (sold separately);Flexibility in Installation - Field convertible from natural gas to liquid propane;PVC venting flexibility (2” up to 75’ & 3" up to 150’);Install indoor or outdoor (outdoor kit sold separately);Improved Efficiency & Reliability - Patented heavy-duty, stainless-steel heat exchanger features only two weld points and eliminates the need for a secondary heat exchanger;Reduced Wait Time for Hot Water - Integrated recirculation pump assists in the delivery of hot water quickly (recirculation plumbing from fixture to unit required);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 and review up to two (2) recirculating schedules using the built-in display;Optional Remote Activation - An optional kit allows the user to engage the heater to recirculate hot water at a touch of a button for on-demand, continuous hot water