What is a heat pump?

Heat pumps transfer existing heat from one place to another, rather than generating it, making them a highly efficient way to heat your home. This article explains how heat pumps work, their benefits, and how they can reduce your carbon footprint and energy bills.

Understanding heat pumps: the basics

What exactly is a heat pump?

A heat pump is an electrical device that extracts heat from a source (like the air or ground) and moves it into your home. Unlike traditional boilers that burn fuel to create heat, heat pumps simply move it, making them much more efficient. They can provide both heating for radiators and hot water, and some models can even offer cooling during warmer months.

How do heat pumps work?

Heat pumps operate using a refrigeration cycle, similar to how a fridge works, but in reverse. They contain a refrigerant that absorbs heat from the outside environment, even when it is cold. This warmed refrigerant then passes through a compressor, which increases its temperature and pressure. The hot, high-pressure refrigerant then transfers its heat to your home's heating system (e.g., radiators or underfloor heating) and hot water tank. As the refrigerant cools and depressurises, it returns to absorb more heat from outside, repeating the cycle.

The science of heat transfer

The efficiency of a heat pump is measured by its Coefficient of Performance (CoP), which indicates how many units of heat energy are produced per unit of electricity consumed. For example, an air source heat pump (ASHP) with a CoP of 3.0 means it produces 3 kWh of heat for every 1 kWh of electricity used. According to Simple Green Energy, ASHPs can achieve efficiencies of 300% or more, meaning they produce at least 3 kWh of heat for every 1 kWh of electricity consumed. This is significantly higher than many gas boilers, which typically operate at lower efficiencies.

Types of heat pumps for UK homes

Air source heat pumps

Air source heat pumps (ASHPs) are the most common type in the UK. They extract heat from the outside air, even in cold temperatures, and use it to warm your home and water. ASHPs are generally easier and less disruptive to install than ground source systems, making them a popular choice for many existing properties. They are effective even in cold UK winters, with modern units designed to perform efficiently across various climates.

Ground source heat pumps

Ground source heat pumps (GSHPs) extract heat from the ground using a network of buried pipes. The ground maintains a more consistent temperature throughout the year than the air, which can lead to slightly higher efficiencies and more stable performance. However, GSHPs typically have higher installation costs due to the excavation required for the ground loops.

Other heat pump systems

While air and ground source heat pumps are the most prevalent for home heating, other types exist. Water source heat pumps, for instance, draw heat from nearby bodies of water. There are also air-to-air heat pumps, which provide heating and cooling through air circulation but do not typically provide hot water for a wet central heating system.

Key benefits of heat pumps for homeowners

Energy efficiency and lower bills

Heat pumps are highly efficient because they transfer heat rather than generate it. This efficiency can lead to lower energy bills compared to traditional fossil fuel heating systems, especially when paired with an optimised electricity tariff. When properly installed, a heat pump can produce three times or more heat energy than the electrical energy it consumes.

Reduced carbon footprint

By using electricity to move heat, heat pumps significantly reduce your home's carbon emissions, particularly as the UK's electricity grid becomes increasingly decarbonised. This makes them a key technology in the transition to a cleaner energy system and helps homeowners contribute to environmental goals.

Consistent comfort and control

Heat pumps provide a consistent and comfortable warmth throughout your home. They typically operate at lower flow temperatures over longer periods, leading to a more even heat distribution than the on-off cycles of a traditional boiler. Modern systems also offer advanced controls, allowing you to manage your home's temperature with precision.

Addressing common concerns about heat pumps

Performance in cold UK weather

A common misconception is that heat pumps are ineffective in cold UK winters. However, modern heat pumps are designed to operate efficiently even when outside temperatures drop well below freezing. While their efficiency might slightly decrease in extreme cold (e.g., below -15°C), this is rare in most of the UK, and they often have backup heating elements to ensure comfort.

Noise levels of modern units

Older heat pump models sometimes had a reputation for being noisy. However, significant advancements in technology mean that modern air source heat pumps are much quieter, often comparable to the hum of a refrigerator. Manufacturers have focused on reducing sound output, making them suitable for residential areas without causing disturbance.

Suitability for older homes

Heat pumps are not just for new builds. Many older, well-insulated homes can be successfully retrofitted with a heat pump system. The key is ensuring adequate insulation and correctly sized radiators or underfloor heating to maximise efficiency. A professional assessment by an MCS-certified installer can determine the best solution for your property.

Heat pump costs, grants, and running expenses

Initial installation costs

The initial cost of installing a heat pump in the UK can vary. According to Thermal Earth, indicative installation costs for an air source heat pump typically range from £7,000 to £15,000 before grants. Ground source heat pumps are generally more expensive due to the excavation required for the ground loops.

Government grants: the Boiler Upgrade Scheme

The UK government offers financial support to help homeowners make the switch to low-carbon heating. According to GOV.UK, the Boiler Upgrade Scheme (BUS) provides a grant of £7,500 for air source and ground source heat pump installations in England and Wales. Households in England and Wales currently using heating oil or LPG may be eligible for an uplifted BUS grant of £9,000 to switch to a heat pump. This increased grant is available until March 2027. To be eligible for these grants, installations must be carried out by an MCS-certified installer, who will apply for the grant on the homeowner's behalf.

Optimising running costs with your energy tariff

While heat pumps are efficient, their running costs depend heavily on electricity prices. Choosing the right energy tariff is crucial. Smart tariffs, often offered by modern energy suppliers, can help optimise running costs by encouraging electricity consumption during off-peak hours when prices are lower and renewable generation is higher. This allows you to heat your home more affordably.

Making the switch to a heat pump

Finding an MCS-certified installer

The first step to making the switch is to consult with an MCS-certified installer. MCS certification ensures that installers meet high quality and safety standards, and it is a mandatory requirement for eligibility for government grants like the BUS. An MCS-certified professional will conduct a tailored home assessment, design a suitable system, and provide an accurate quote.

Preparing your home for a heat pump

Proper preparation is essential for optimal heat pump performance. This often involves assessing and potentially improving your home's insulation, ensuring your radiators are appropriately sized for lower flow temperatures, or considering underfloor heating. These steps maximise the heat pump's efficiency and ensure your home stays warm and comfortable.