Can a heat pump provide Domestic Hot Water (DHW)?

The simple answer to this is yes. However you need to carefully consider the implications on running costs. As the outlet temperature of the heat pump increases the efficiency of the heat pump decreases, basically the heat pump has to work harder to achieve the higher temperature. Efficiencies of heat pumps are quoted as the Coefficient of Performance (COP). For an outlet temperature of 35°C the COP is 4, i.e. for every one unit of electricity used, 4 units of heat energy are produced. However while 35°C is fine for underfloor heating, it is not hot enough for DHW. Therefore when producing DHW the heat pump outlet temperature needs to be increased to the heat pumps maximum of approx 50°C. At this temperature the COP of the heat pump drops to 3, i.e. a 25% drop in efficiency. If these running costs and the lower DHW temperature (50°C) are acceptable then there is now problem with the heat pump producing DHW. We would also recommend that an additional ground array (slinky) is used due to the additional demand on the ground.

A much more cost effective way of producing DHW would be to use solar panels backed up with an off-peak immersion heater.

Check out our fact sheet on Ground Source Heat Pump and domestic hot water production.