The Marey GA10NG Indoor Natural Gas Tankless Water Heater can provide up to 4.3 gal. per minute for a perfect shower at 115F output water temperature. It is also called water heater on demand, because it heats water only when needed, saving energy. It is designed to supply endless hot water for up to 2 or 3 points of use simultaneously (for a variety of residential hot-water applications). Its compact design saves space and is easy to install: you will only need 2-D cell battery for the ignition and a venting (not included in the box). Marey has been on the water heating business since 1955, bringing tradition and innovation together.