ecoTough Series: Noritz introduces the latest advancements in tankless water heater technology for your home. The ecoTough High-Efficiency Series gives you unparalleled reliability and quality engineering and construction. It reduces energy use and CO2 emissions. The main features are endless hot water, less expensive PVC vented installation, and long life and reliability. Tankless Water Heater: A major improvement to the standard tank style water heaters, the NRC661 series tankless water heater packs a lot of power in a small package. The compact and efficient Noritz NRC661 saves space, energy and water while delivering endless hot water for mid to large size residential applications. If your hot water needs expand, the quick-connect system enables multiple heaters to be connected and run by the same controller system in the same efficient and effective manner. All of this functionality and efficiency are seamlessly controlled by a self-diagnostic computer system, ensuring the safety of your home and that there is always perfect non-varying hot water for everyone to enjoy. Features:: High-efficiency low NOx Eco-Burner reduces emissions Liquid Propane tankless hot water heater Approved for Outdoor Use ecoTough tankless condensing heater Thermal efficiency: 92% Energy Star Factor: 0.91 Cold and Hot water connection size: 3/4" Gas connection size: 1/2" Power Supply: 120 VAC (60 Hz) Exhaust vent diameter requirements: 3" Exhaust vent material requirement: PVC or CPVC 5 Year Parts Warranty 1 Year Labor Warranty