LBNL Report Number
A forty gallon residential gas-fired storage water heater was modeled under Department of Energy test procedure conditions using the TANK simulation program. The purpose was to determine heat flows in a typical residential storage water heater that meets the current minimum efficiency standards. Modeling showed that, without considering a condensing water heater design, the greatest potential efficiency gains can be made by reducing flue losses during the non-firing, non-recovery mode, i.e., during standby mode. The stack losses while in standby mode account for about 43% of heat losses (not including the energy added to deliver hot water), and 17% if hot water energy is included.