Domestic Hot Water

Determining the primary water heating system

HPXML allows for the specification of several WaterHeatingSystem elements. HEScore only allows one to be specified. If there are more than one water heaters present in the HPXML file, the one that serves the largest fraction of the the load is selected based on the value of FractionDHWLoadServed. If not all of the WaterHeatingSystem elements have FractionDHWServed subelements (or if none of them do), the first WaterHeatingSystem is selected.

Water heater type

The water heater type is mapped from HPXML to HEScore accordingly:

HPXML to HEScore water heater type mapping
WaterHeaterType DHW Category DHW Type
storage water heater unit storage
dedicated boiler with storage tank
instantaneous water heater [1]
heat pump water heater unit heat_pump
space-heating boiler with storage tank combined indirect
space-heating boiler with tankless coil combined tankless_coil

The fuel type is mapped according to the same mapping used in Primary Heating System Fuel mapping.

Water heating efficiency

If the WaterHeatingSystem/EnergyFactor element exists, that energy factor is sent to HEScore. When an energy factor cannot be found, HEScore can accept the year the equipment was installed and estimate the efficiency based on that. The year is retrieved from the YearInstalled element, and if that is not present the ModelYear element.


[1]The HEScore help instructs, “If the water heater is a tankless model (aka: on-demand or instantaneous water heater) it should be characterized the same as a storage model that uses the same fuel. An electric tankless should be entered as Electric Storage, a natural gas tankless should be entered as Natural Gas Storage, and an LPG or propane tankless should be entered as LPG Storage.”