What Are the Advantages of a Heat Pump Water Heater?
What are the advantages of a heat pump water heater? The main advantages of a heat pump water heater are lower electricity consumption, reduced hot water running costs, and much higher energy efficiency compared with conventional direct electric water heating. Instead of using electricity solely to generate heat through an immersion heater, a heat pump water heater extracts thermal energy from the surrounding air and transfers it into the stored domestic hot water (DHW). This means it can typically deliver several units of heat for every unit of electricity consumed.
Heat Pump Water Heaters Use Less Electricity
One of the biggest advantages of a heat pump water heater is its ability to reduce the amount of electricity required to produce hot water.
A conventional electric immersion heater uses resistance heating. Approximately 1 kWh of electrical energy is converted into around 1 kWh of heat before system losses are taken into account.
A heat pump water heater works differently. A fan draws air across an evaporator, allowing refrigerant to absorb heat from the air. The compressor increases the temperature and pressure of the refrigerant before a condenser transfers this energy into the water.
Because the system is transferring heat rather than producing all of it directly from electricity, substantially less electrical energy is required.
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High Coefficient of Performance
The efficiency of a heat pump is commonly described using its Coefficient of Performance, or COP.
For example, if a heat pump water heater has a COP of 3 under particular operating conditions, approximately 1 kWh of electricity is used to deliver around 3 kWh of heat into the domestic hot water.
This makes heat pump technology considerably more efficient than direct electric resistance heating.
The actual COP will vary according to factors such as:
- Source air temperature
- Hot water storage temperature
- Refrigerant
- Compressor performance
- Hot water demand
- Heat losses
- Operating conditions
UK guidance and manufacturer information commonly highlight this ability to produce multiple units of heat from each unit of electricity as one of the principal benefits of heat pump water heating.
Lower Domestic Hot Water Running Costs
Lower electricity consumption can translate directly into lower domestic hot water running costs.
This can be particularly attractive in properties where hot water would otherwise be produced using an electric immersion heater.
The actual saving will depend on the electricity tariff, household hot water consumption, heat pump efficiency, storage temperature, and how frequently any supplementary immersion heater is used.
Correctly sized systems can allow the heat pump to meet the majority of daily DHW demand while reserving direct electric heating for occasional boosting, backup or higher-temperature cycles.
Ideal for All-Electric Properties
A dedicated air source heat pump water heater can be particularly useful for homes, flats, and apartments without a mains gas connection.
Unlike a conventional whole-house air source heat pump, a heat pump water heater is specifically intended to produce domestic hot water. It does not necessarily need to provide space heating to radiators or underfloor heating.
This makes it possible to improve the efficiency of hot water production without replacing the property’s entire heating system.
Heat Pump Water Heaters Work Well With Solar PV
Another important advantage is the ability to combine a heat pump water heater with solar photovoltaic panels.
Instead of exporting surplus solar electricity to the grid, some of that electricity can be used to operate the heat pump and heat the water stored within the cylinder.
The hot water cylinder can therefore act as a form of thermal energy storage.
Energy generated by the solar PV system during daylight hours can be stored as hot water and used later for showers, baths, washing up, and other domestic hot water requirements.
With suitable controls, operation can also be scheduled around periods of high solar generation or lower-cost electricity tariffs.
Reduced Reliance on Immersion Heaters
Many heat pump water heaters incorporate an electric immersion heater, but it does not necessarily need to operate as the main heat source.
The heat pump can provide the majority of everyday water heating, while the immersion heater is available for:
- Backup heating
- Rapid boosting
- Peak hot water demand
- High-temperature hygiene cycles
Reducing the amount of time an immersion heater operates can significantly reduce electrical consumption compared with a cylinder that relies entirely on direct resistance heating.
They Can Use Otherwise Unwanted Heat
Heat pump water heaters can also recover useful energy from warm air.
For example, a unit installed in a suitable utility room or plant room may be able to extract heat generated by appliances, equipment, or other sources within the space.
As the evaporator removes heat from the air, it also provides a degree of cooling and dehumidification.
This can be an additional benefit in suitable garages, utility rooms, and plant spaces, although the installation must always meet the airflow and operating requirements specified by the manufacturer.
Lower Carbon Impact
Because a heat pump water heater requires less electricity to produce a given quantity of useful heat than direct electric resistance heating, it can also reduce the carbon emissions associated with producing domestic hot water.
This benefit can increase further when electricity is supplied from renewable sources such as solar PV or a low-carbon electricity tariff.
Modern heat pump water heaters may also use R290 refrigerant, or propane, which has a very low Global Warming Potential compared with many traditional fluorinated refrigerants.
Are Heat Pump Water Heaters Worth It?
For many UK properties, the combination of high energy efficiency, reduced electricity consumption and lower hot water running costs makes a heat pump water heater particularly attractive, especially when replacing a conventional electrically heated hot water cylinder.
The greatest benefits are normally achieved when the system is correctly sized around cylinder capacity, household occupancy, daily hot water demand, shower flow rates, recovery time, source air temperature, and required storage temperature.
When these factors are considered properly, an air source heat pump water heater can provide an efficient method of producing domestic hot water while substantially reducing reliance on direct electric immersion heating.