Will a Heat Pump Provide Enough Hot Water for Baths, Showers and Domestic Purposes?

With the correct design and equipment, all domestic hot water requirements would be provided by the air source or ground source heat pump throughout the year.  Heat pumps produce water at a lower temperature than boiler systems.  Instead of water that may be scalding, and hence possibly dangerous, water produced is hot enough for normal domestic requirements.  The aim is to save money and energy with either an air source or ground source system.

Heat pump systems use the ambient temperature of either the air or ground to provide domestic heating and hot water.  Air source heat pumps absorb low temperature heat from the air into a refrigerant fluid.  This fluid then runs through a compressor, which increases its temperature.  The heated fluid runs in a coil through water that is used in the heating and hot water circuits in your home.  Ground source heat pumps work in a very similar manner but instead, they absorb heat from the ground through fluid-containing loops that are buried either horizontally or vertically in bore holes, depending on the space you have available.

Once the water is heated by the heat pump systems it is stored in a tank ready for use.  This tank needs to be well insulated to prevent heat loss.  With a conventional boiler, domestic hot water is usually stored at 60-65°C, however heat pumps can normally only heat water to about 45-50°C, so it is also likely that occasional temperature boost will be needed.  The water tank used with ground and air source heat pumps will usually contain a heating element.

The maximum temperature of the hot water depends on a number of factors, such as the type of refrigerant used in the heat pump, the size of the coil in the hot water tank, the usage, etc.  Changing the refrigerant can cause the heat pump to operate at higher temperatures and heat water up to 65°C, however heat pump systems are less efficient at higher temperatures.  The size of the coil within the tank is very important: if the coil is too small, hot water will not reach the required temperature.  When using a heat source or ground source heat pump it’s necessary to have a very large heat-exchanger coil.