Rheem Water Heaters offers two new on-demand, tankless gas water heaters for residential and commercial applications. Marketed under the trade name Pronto!™, these energy-saving units have no standing pilot light and no storage tank, eliminating the need to maintain a large supply of pre-heated water. The Pronto! RTG-42PV instantaneously delivers up to 4.2 gallons of 100° to 140°F water per minute (at a 45°F rise in temperature), with a Btu/hr range of 31,500 to 118,000. The Pronto! RTG-74 whole-house model, which is also suitable for commercial applications, provides up to 7.4 gallons of 100° to 140°F water per minute and features Btu/hour inputs from 21,700 to 199,000. Rheem Water Heaters.