What is a Heat Pump? Everything You Need to Know.

We have all heard of heat pumps as they become increasingly popular in the UK. Despite this rise in popularity, they only contribute to about 1% of the heating industry in the UK, with traditional gas boilers taking 95% of the pie.

According to the government, gas boilers will no longer be installed in new houses from 2025, which means there will be a high demand for heat pumps. But is it time for you to throw out your gas boiler?

We have all the answers you need on what a heat pump is, how it works, and the different models available, as well as the cost.

What Are Heat Pumps?

What are heat pumps

A heat pump is a system installed outside of the home that helps to heat and cool the home.

During the cold winter months, your heat pump is able to take heat from the air or ground outside and transfer it into your home. During summer it does the opposite and takes the heat from inside your house to transfer it outside, cooling your house and making summer-sweats bearable.

Unlike a gas boiler, a heat pump system runs on electricity and not fossil fuels, making them more sustainable (especially when solar panels are installed) and eco-friendly.

There are three main types of heat pumps: ground source, air source, and water source heat pumps.

The Workings Of A Heat Pump

Taking natural heat from the air or ground outside they provide your home with heating and hot water.

Basic workings of a heat pump

Although there are different types of heat pumps (more on that later), here are the basic workings of a heat pump:

Absorb heat

A heat pump absorbs heat from the air, water, or ground (depending on the type of pump) and runs it through a refrigerant. This happens in an evaporator, where the refrigerant transforms from liquid to gas.

Compressed gas

The gas refrigerant is compressed, which increases the temperature. This increased temperature from the compressed gas can then be used to power your heating systems, ensuring toasty radiators or underfloor heating. This occurs in the heat exchanger, where the heat from the gas is transferred to your heating system.

Condensing to liquid

As heat is removed from the compressed gas refrigerant, the gas condenses and becomes liquid once again. This process occurs in a separate heat exchange chamber. The heat from the cooling liquid can still be absorbed by the central heating system in this exchange chamber.

Repeat the process

When the liquid refrigerant is cool it flows through the expansion valve. From there, the pressure of the liquid decreases and it flows back into the evaporator, where the entire cycle restarts.

How does a ground source heat pump work?

A ground source heat pump can extract heat straight from the ground. This is done through a series of pipes that are located on the ground and a combination of water and antifreeze (known as refrigerant) within these pipes. The liquid solution extracts heat, which stimulates the process explained above.

How does an air source heat pump work?

This type of pump is basically like the reverse of a refrigerator.

The outside air flows over pipes containing refrigerant. The heat is then extracted from the air, which kick-starts the heating process as explained above.

How does a water source heat pump work?

A water source option works with a similar process as above, but instead, heat is extracted from a source of water, such as a pond, lake or groundwater in a well.

How To Use A Heat Pump At Home

Heat pumps can be used at home to heat up the water in your hot water cylinder and also to provide heating to your home.

They are the most efficient when the inside and outside air temperature is not vastly different. This concept is similar to how a fridge has to work much harder to cool down your food when it is hot outside.

Heat pumps are great for underfloor heating, as your floors do not have to get as hot as radiators due to the large space they cover.

They also have a lower heat output than traditional fossil fuel boilers, which means they are not able to heat your house as fast. They are best when given a lot of time to heat your home slowly but consistently.

Heat pumps for radiators

Heat pumps for radiators

If you are switching from a gas boiler or combi-boiler to a heat pump to heat your radiators, you may have to consider buying some larger radiators.

Similar to underfloor heating, larger radiators will cover more space inside, which will help to keep your home cosy as the radiators won't heat up as fast as gas boilers.

Heat pumps for hot water

Heat pumps can be used to provide hot water to your taps; however, the temperature of the water would be slightly cooler than if you had a traditional boiler.

In practice you may have to use more hot water and less cold water if you want to take a hot bath or shower. Practically you may also have to consider a larger hot water cylinder.

Advantages And Disadvantages Of Heat Pumps

Whether ground, water or air source heat pumps, each has several advantages and a couple of disadvantages. Listed below:


  • Efficient when it comes to heat production for home heating and hot water.
  • Reduced carbon footprint because not dependent on fossil fuels.
  • Homeowners could be eligible for a £5,000 discount to install a heat pump with the Boiler Upgrade Scheme.
  • An air source heat pump is easy to install.
  • They can last for many years with fairly little maintenance.
  • Some heat pump systems can act as cooling systems in the hot months.


  • Radiators are only warm, not boiling hot.
  • Great for maintaining an ambient temperature but not suddenly increasing the temperature.
  • High installation costs.
  • Installation can take up to eight days for ground source heat pumps.
  • An outside heat pump requires outside space, as well as space inside for the water tank.

Heat Pump Costs

How much it costs to install a heat pump

There are a couple of costs involved with heat pumps, such as the installation, maintenance and running costs.

How much does it cost to install a heat pump?

Unfortunately, installing a heat pump is more costly than a gas or oil boiler.

Depending on the brand, the cost could be between £12,000 and £17,000.

Apart from the purchase price, you will also have to pay for installation. If you are installing underfloor heating or larger radiators, the pounds will add up.

You will also have to consider if you need to re-insulate your home. Although these heating systems are efficient at maintaining a high ambient temperature, they do not fare well in poorly insulated spaces.

Fortunately, the government offers £5,000 to homeowners who want to upgrade to a heat pump system through the Boiler Upgrade Scheme.

How much does it cost to run a heat pump?

Once the pump is installed, you will have an incredibly efficient heating system in your home.

Traditional boilers have a 90% efficiency, meaning you lose around 10% of the heat generated.

Heat pumps have an estimated efficiency of around 350% in comparison.

Of course, energy prices and our homes vary, so it is hard to calculate the exact running costs of your heat pump, but with this energy-efficient system and no reliance on expensive fossil fuels, you cannot go wrong with a heat pump if you are concerned about ongoing costs.

How much does it cost to maintain a heat pump?

Heat pumps are built to last, so you don't have to have regular maintenance or expect a lot of repair costs.

You should get a professional service for your ground or air source heat pumps at least every two years. Some manufacturers may recommend you get an annual service to maintain the warranty.


What is the biggest con of a heat pump?

The main disadvantage of a heat pump is the high initial cost to purchase and install the pump.

Why is my heat pump not working?

If your heat pump is not efficiently heating your home, there could be several reasons:

  • The unit is too small to heat your home.
  • Your house is poorly insulated (especially with an air source heat pump).
  • The system has not been maintained and requires a service.

How long do heat pumps last?

Heat pumps are built to last. However, you can expect your water, ground or air source heat pump to last for at least 15 years. Some of the newer models can last even longer.