Noritz. The Energy Star-rated EcoTough Series NRC98 gas-fired residential condensing tankless on-demand water heater has an Energy Factor of 0.93 and operates with a maximum flow rate of 9.8 gpm and temperature settings from 100 degrees F to 140 degrees F. Featuring a commercial-grade heat exchanger, the unit is covered by a 12-year, 6,500-hour warranty. 866.766.7489. www.noritz.com.