What is a domestic heat pump and how does it work?

Heat pumps for domestic settings work in the same way as those for larger commercial applications.

They transfer heat extracted from an environmental source such as the air, ground or a body of water which has absorbed the heat of the sun. Using a refrigeration cycle and heat exchanger this heat is gathered and transferred to your home to supply your central heating system and hot water cylinder.

Heat pumps designed for domestic use are simply a little smaller and less powerful than those used very large buildings.

Whereas commercial systems tend to be controlled by complex building management software domestic heat pumps will usually have their own control software and often a simple app interface is available to make changing settings easy. 

Typically, UK domestic heat pumps will work on a single phase electrical supply - a standard UK domestic electric supply - whereas larger commercial units will require a 3 phase electric supply.

More detail on how heat pumps work.

Is it worth getting a heat pump in the UK?

If you are building a new home then the cost differential with installing a boiler driven system is not very large and your building will be future-proofed against the phasing out of traditional gas and oil boilers. 

If you are refurbishing an existing property you can get funding to help cover the additional costs involved in converting your heating system.

Even if your older home cannot have further energy saving measures applied to it, a heat pump can still be worthwhile. Your energy consumption will always reflect the thermal energy required to heat your home.

In both cases a heat pump can help insulate you against fluctuations in fuel prices, particularly if you invest in generating and storing your own electricity with integrated solar panels and battery storage. 

You may also wonder if it is expensive to run a heat pump, given that electricity is more expensive per unit than gas or oil currently. Heat pumps however don't use electricity to generate heat directly, only to run a compressor and circulation pumps. As it is far more efficient to collect and move heat rather than generating it by burning fuels, fuel costs can be comparable or lower in a well designed system. 

Heat pumps are entirely suitable for the UK climate and work well even in cold weather with a freezing outdoor temperature. They are perfectly capable of reaching and maintaining a desired temperature in your home down to outside air temperatures as low as -25 degrees celcius. 

Is a heat pump better than other kinds of central heating?

There are benefits to heat pumps compared to a gas boiler or other oil boiler. 

They are indisputably better for the environment with no emissions at the point of use and much lower carbon emissions than other heating systems that burn fuel. 

Many models also have the ability to offer both heating in winter and cooling in the summer months, offering year-round climate control and comfort. This can remove the need for a separate air conditioner unit in the UK where there are a limited number of very hot days requiring a dedicated cooling function. 

If you want to know more about how heat pumps compare to other types of heating then read our article about eco friendly heating systems and how heat pumps compare to other options.

Types of heat pumps for domestic settings

There are domestic versions of most heat pumps on the market.

Heat pumps can provide fully-controllable heating, hot water, and comfort, with minimal maintenance required.

There are a number of sub-types of heat pumps which it can be useful to understand when considering possible choices for your home.

The first choice to be made is between and air source or a ground source heat pump (also called geothermal heat pumps). As the names suggest the main difference between these two types of heat pumps is where they extract heat from - with air source heat pumps taking heat from the air and ground source heat pumps taking heat from the ground or water.

Air source heat pumps are usually installed outside to absorb heat directly from the outside air in domestic settings, although sometimes they are installed indoors and can, for example, repurpose waste heat in ambient air from industrial processes in commercial settings.

Ground source heat pumps are usually installed inside and are connected to a collector loop outside which is buried or laid in water to collect the thermal energy stored from the sun. 

You can read more about the difference in the way these two types of heat pumps work and are installed in detail on our full articles on ground source heat pumps and air source heat pumps. But below is a short outline of some of some variants if system for each type.

Different types of air source heat pumps

Monobloc vs split air source heat pumps

The terms ‘split’ and ‘monobloc’ refer to how a heat pump is set up in a home. 

In a monobloc system, the heat pump has all of its components (apart from the hot water cylinder which is installed inside the home) located inside a heat pump unit situated outside the home. 

A split heat pump unit, however, has both an outside unit, which incorporates the heat exchanger and an internal unit, which sits inside the property, usually in a utility or boiler room. 

Most homes in the UK are best suited to a monobloc air to water heat pump and these are by far the most popular units on the market

Split systems are more popular in countries with very cold winters, due to there being less chance of a system freezing as all the water pipes are part of the inside unit. However, a split system gives some flexibility as they can be installed further away from the property to be heated, and making them a choice for more complex situations. 

Ground or air to water vs air to air source heat pumps

Air or ground to water heat pumps make up the vast majority of heat pump installations in the UK with ground to water being the next most popular. 

These types of heat pump work by transferring heat from a heat source (the air or ground) to a store of water in your home. This makes them the most similar type of heat pump to boiler-fed central heating systems which also create hot water to feed a central heating system and hot water supplies (though of course boilers generate heat by burning fuel rather than harvesting heat energy from the environment).

Air to air source heat pumps use the heat collected from the air to heat the air of your home directly rather than transferring heat to a store of water and then a radiator or underfloor heating system. 

Air to air source heat pumps do not heat hot water and cannot be connected to existing central heating systems which rely on hot water like wet underfloor heating or radiators. If used for heating then an alternative method for providing hot water must be considered. For this reason they are less popular than air to water systems in domestic settings. 

High temperature heat pumps - a type of air or ground to water heat pump

Heat pumps are most efficient when working with low flow temperatures around 35°C to 45°C whereas it is usual to have a boiler set at around 65°C . Some air source source heat pumps and ground source heat pumps operate at a maximum flow temperature of 55°C.

In order to change an existing central heating system to work efficiently with a heat pump it is often therefore recommended to upsize of radiators or switch to underfloor heating to increase the heat exchange surface of heat emitters. This means even though the flow temperatures through the system are lower, it won't take an age to heat a room up to the desired temperature.

Lower flow temperatures also mean that hot water cylinders may need to be larger to provide the same volume of mixed water as a boiler fed system. 

Some heat pumps are designed specifically to provide higher flow temperatures up to 75°C to address situations where a fast response is required (typically older homes) or there is a need for high volumes of hot water but there is not space for large cylinders.

Your heat pump’s compressor works harder when there’s a larger temperature difference between the outside and the water needed in your home to provide your desired room temperature. The less the compressor needs to work, the less electricity the heat pump uses. There is thus a trade off in terms of heating costs and how energy efficient your system will be if using a heat pump to heat water to a higher a temperature, but properly designed systems can still cut carbon emissions and exhibit high energy efficiency, exceeding that of an oil or gas boiler. 

Hybrid heat pump system

It is possible to install a heat pump alongside another heat source such as a boiler. Whilst in domestic settings backup systems are not usually required to support critical operations, hybrid heat pump systems are sometimes used where there is an existing heating system already in place that is in good working order.

In these situations, rather than completely jettison an existing functional system, a smaller heat pump can then be installed to cover the heating load for most of the heating season, with the boiler coming online only for the very coldest days of the year. 

This is an increasingly rare scenario as higher temperature heat pumps have come onto the market and can be set to react to colder weather, but still may be an option for some larger, older properties. 

How much does a domestic heat pump cost?

The cost of a heat pump installation is influenced by the size of your home, the type of heating system you’re replacing, and the complexity of the installation. Beware of deals that promise a fixed price without taking account of your home: such installations are unlikely to be well designed and provide the benefits you are seeking. 

The total price of buying and installing an air source heat pump is typically £10,000 - £14,000. 

In England and Wales you may be eligible for the government’s Boiler Upgrade Scheme (BUS) if you’re replacing your fossil fuel-powered gas boiler, which offers a £7,500 grant towards the overall cost. 

To be eligible for the grant, a valid, Energy Performance Certificate (EPC) from the last 10 years, with no recommendations for cavity wall or loft insulation is required.

You can find out more about the various current funding schemes and financial assistance available in your home nation in our article on funding for renewable energy measures.

Installation and Maintenance of a domestic heat pump

The installation itself typically takes between three and five days, depending on how large and complex the installation is. Additional time may be required for ground works if you choose a ground source heat pump. 

Heat pumps require minimal maintenance, but regular checks and servicing can help ensure optimal performance. An annual service by a qualified heating engineer is recommended 

You can find more detail about installation in our articles about:

Ground source heat pump installation

Air source heat pump installation 

A ground source installation step by step