How do heat pumps work?

Heat pumps are a strategic upgrade for your home's heating, offering an abundant supply of warmth by moving heat rather than generating it. This makes them highly efficient, providing a clear path to greater control over your home's energy. Forget the old scarcity mindset; heat pumps are a power play for modern living, designed to work effectively even in the UK's varied climate.

The fundamental principle of heat pumps

Unlike traditional boilers that burn fuel to create heat, heat pumps operate on a different, more efficient principle: they transfer existing heat from one place to another. This core difference is what makes them such a powerful tool in modern home heating.

Heat transfer, not generation

The key to a heat pump's efficiency lies in its ability to extract heat from a source - be it the air outside your home or the ground beneath it - and then release that heat into your living spaces. This process is far more efficient than burning fossil fuels, as it simply moves energy that is already present. Heat pumps can achieve impressive efficiencies, often reaching 300% or more. This means that for every unit of electricity they consume, they can produce three or more units of heat for your home.

The refrigerant cycle explained

At the heart of every heat pump is a refrigeration cycle, much like the one found in your fridge or freezer, but in reverse. This cycle involves a special fluid called a refrigerant, which changes between liquid and gas states to absorb and release heat.

The process begins when the liquid refrigerant, at a very low temperature, absorbs heat from the external environment (air or ground). This causes the refrigerant to evaporate and turn into a gas. This now warm gas is then compressed, which significantly increases its temperature. The hot, high-pressure gas then flows into a condenser coil inside your home, where it releases its heat to your heating system (radiators or underfloor heating). As it cools, the refrigerant condenses back into a liquid. Finally, the liquid refrigerant passes through an expansion valve, which lowers its pressure and temperature, preparing it to absorb more heat from the outside and restart the cycle.

Key components of a heat pump system

A heat pump system is a sophisticated piece of engineering, but its main components work together in a straightforward cycle to deliver warmth.

Evaporator, compressor, condenser, and expansion valve

Each heat pump contains four primary components that facilitate the refrigerant cycle:

• Evaporator: This is where the refrigerant absorbs heat from the outside source (air or ground) and turns into a low-pressure gas.
• Compressor: This component increases the pressure and temperature of the refrigerant gas, making it hot enough to heat your home.
• Condenser: Inside your home, the hot, high-pressure refrigerant gas releases its heat to your heating system, condensing back into a liquid.
• Expansion valve: This valve reduces the pressure and temperature of the liquid refrigerant, allowing it to return to the evaporator and begin the cycle anew.

The role of refrigerant

The refrigerant is the lifeblood of the heat pump. It is a carefully selected fluid with a very low boiling point, allowing it to easily absorb heat from cool environments and release it at higher temperatures. Modern refrigerants are chosen for their efficiency and environmental impact, ensuring the system operates effectively and responsibly.

Different types of heat pumps

While all heat pumps work on the same fundamental principle, they differ in how they extract heat from their environment. The two most common types for UK homes are air source and ground source.

How air source heat pumps work

Air source heat pumps extract heat from the outside air, even when temperatures are low. They draw air over an evaporator coil, which contains the refrigerant. The refrigerant absorbs the latent heat from the air, even if it feels cold to us, and then transfers it into your home.

How ground source heat pumps work

Ground source heat pumps tap into the stable temperatures found beneath the earth's surface. They use a network of pipes, known as ground loops, buried in your garden. These loops circulate a mixture of water and anti-freeze, which absorbs heat from the ground. The underground temperature typically remains within the 8-10°C range year-round, providing a consistent and reliable heat source.

Other heat pump variations

While air and ground source are the most prevalent, other types exist, such as water source heat pumps, which draw heat from nearby bodies of water. For most UK homeowners, the choice will primarily be between air and ground source systems, depending on property type, available land, and budget.

Heat pumps in the UK climate: winter performance

A common misconception is that heat pumps struggle in cold weather. However, modern heat pumps are designed to perform exceptionally well in the UK's climate.

Extracting heat from cold air and ground

Air source heat pumps can operate effectively in outdoor temperatures as low as -15°C, and some models can even provide heat at -20°C to -25°C, though their efficiency may reduce at these extreme lows. The UK rarely experiences such prolonged severe cold, meaning your heat pump will keep your home warm and comfortable throughout the winter. Ground source heat pumps, on the other hand, benefit from the consistent underground temperatures, making them less susceptible to external temperature fluctuations.

Maintaining efficiency in lower temperatures

To maintain optimal efficiency in colder conditions, heat pumps are often designed to run at lower, more consistent temperatures over longer periods, rather than in short, high-heat bursts like a traditional boiler. This steady operation ensures a comfortable indoor climate without overworking the system. Good home insulation is crucial for any heating system, but it is particularly important for heat pumps to maximise their performance and keep running costs down. For more ways to keep your home warm, explore our energy efficiency tips.

Why heat pumps are an energy power play

Choosing a heat pump is more than just an energy upgrade; it is a power play that puts you in control of your home's heating, offering significant benefits for your wallet, your comfort, and the planet.

High efficiency and reduced running costs

Heat pumps are incredibly efficient, converting one unit of electricity into three or four units of heat. This high efficiency translates directly into reduced running costs compared to traditional fossil fuel systems. While electricity costs more per unit than gas, the sheer efficiency of heat pumps often makes them cheaper to run, especially when replacing liquefied petroleum gas (LPG), oil, or electric boilers.

Environmental benefits and carbon reduction

By transferring heat rather than burning fossil fuels, heat pumps significantly reduce your home's carbon emissions. When powered by renewable electricity, they can offer entirely carbon-free heating, making a substantial contribution to a greener future. This aligns with Fuse's vision of rebuilding the energy system and moving beyond outdated heating methods.

Enhanced home comfort and control

Heat pumps provide a consistent, comfortable warmth throughout your home, avoiding the sharp temperature fluctuations often associated with traditional systems. With smart controls and apps, you gain granular control over your heating, allowing you to optimise performance and energy usage. Fuse's app-first approach aims to provide clear data on heat pump performance and energy usage, empowering you with real-time insights into your energy consumption. Pairing this with a smart meter installation can further enhance your understanding of energy use.

Is a heat pump right for your home?

Deciding if a heat pump is the right choice for your home involves considering several factors, from your property's characteristics to available financial support.

Factors influencing suitability and performance

The suitability of a heat pump largely depends on your home's insulation levels, size, and existing heating system. While heat pumps can be installed in most properties, a well-insulated home will always achieve better efficiency and lower running costs. It is also worth noting that heat pumps typically work best with larger radiators or underfloor heating systems, as they operate at lower flow temperatures than traditional boilers.

Understanding installation and system integration

Installing a heat pump is a significant home improvement. The UK government offers financial incentives, such as the Boiler Upgrade Scheme (BUS), to help homeowners with the upfront costs. This scheme provides a grant of up to £7,500 towards the installation of an air or ground source heat pump in England and Wales. To be eligible for such grants and certain warranties, heat pump installations must comply with the Microgeneration Certification Scheme (MCS) standards. MCS certification ensures that both the heat pump product and its installation meet rigorous quality and safety benchmarks. You can learn more about the scheme in our detailed guide to the BUS explained.

Choosing a heat pump is a forward-thinking decision, offering an abundant comfort upgrade and a powerful step towards energy independence.