## 5.7 B7.2. Small consumer Gas or Oil Instantaneous Water Heater

The hourly energy use for instantaneous gas or oil water heaters is given by Equation 34, where the nominal rating is multiplied by 0.92 to reflect the impacts of heat exchanger cycling under real world load patterns.

WHEU = HARL j j EF j × 0.92 | Equation 34

where |
WHEUj | = | Hourly fuel energy use of the water heater (Btu).
HARLj | = | Hourly adjusted recovery load.
EFj | = | Energy factor from the DOE test procedure (unitless). This is taken from manufacturers’ literature or from the CEC Appliance Database.
0.92 | = | Efficiency adjustment factor