The RTG-74 is a new tankless gas water heater in the PRONTO! line that delivers a continuous supply of 100°F to 140°F water at a flow rate as high as 7.4 gallons per minute. It is a compact unit the size of a medicine cabinet and comes in four models, including indoor and outdoor versions that are powered by either natural gas or LP gas. Btu/hour inputs range from 19,000 to 199,900.