The heating of domestic hot water is considered when calculating the dwelling energy use in DEAP.

Key considerations

When you survey a domestic hot water system, key considerations are the heat source, auxiliary heat source (such as a solar thermal system), type of hot water storage, heating controls, showers and baths.


The domestic hot water (DHW) demand calculation in DEAP is based on the SAP methodology (SAP 10). It is derived from the dwelling floor area and takes account of heating, storage and distribution losses plus several other parameters. The requirements for domestic hot water are covered in Section 4 of the DEAP manual.

Water efficiency

Hot water usage in DEAP is reduced by 5% if the dwelling is designed to achieve a total water use target of not more than 125 litres per person per day. You can use the water efficiency calculation tool to demonstrate that this water use target has been met.

This is an optional calculation that is not required as part of a BER for a dwelling.


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