Navien NPE-A series is the most advanced condensing tankless water heaters in the industry with exclusive ComfortFlow® technology for continuous hot water. Navien ComfortFlow® is the first and only system that incorporates a built-in insulated buffer tank and recirculation pump. The buffer tank eliminates the “cold water sandwich” effect and issues of minimum flow rates commonly found in other tankless water heaters. The recirculation pump saves on water bills by reducing the time to get hot water. When activated, the optional ComfortFlow mode results in additional energy usage.