Heat Pumps and Underfloor Heating Explained

Heat pumps are becoming an increasingly popular heating choice in the UK, supported by government incentives due to their potential for high efficiency and lower carbon emissions. But how do they work, and how do you ensure they operate efficiently in a real home? This page explains the key things homeowners and installers should understand before installing a heat pump.

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What is a heat pump and why is the UK switching to them

Simply put, heat pumps use electricity to move heat from one place to another (from the ground, water or outside air), rather than generating the heat directly from fuel or electricity. This thermal energy warms a refrigerant, which is then compressed to increase its temperature before transferring heat into your home’s heating system. (like radiators or underfloor heating). This is central to the UK’s long term net zero strategy.

When paired with low temperature heat emitters such as underfloor heating, heat pumps can use one unit of energy to move as much as 3 – 6 units of thermal energy. This ratio is called their COP (Coefficient of performance). When averaged out over seasons this is known as as Seasonal Coefficient of Performance (SCOP). Compared to a boiler that uses one unit of energy to make at best 0.95 units of heat. This makes heat pumps under the correct circumstances run more than 3 x (or more!) as efficiently as boilers!

To maintain a high SCOP, heat pumps must operate at low flow temperatures (typically below 55C, which requires a well-insulated home and correctly sized heat emitters.

air source heat pump

The main two types of domestic heat pumps explained

Air source heat pumps (ASHP) are situated outside and use a fan to draw in thermal energy from the air. Their efficiency and maximum heating output are directly affected by the outdoor temperature, however they can continue operating effectively even during sub-zero outdoor temperatures. When paired with a low-temperature heat emitter users report an average COP of 3 – 4.

Ground source heat pumps (GSHP) extract heat from the ground or groundwater using buried pipes, known as a ground loop. The ground temperatures are more stable throughout the year and GSHP deliver less seasonal results. When paired with a low-temperature heat emitter we have had users reporting COPs of 3.5-6.

  • Boiler = up to 95% efficiency
  • Air Source Heat Pump = 250% to 400%
  • Ground/Water Source = 350% to 600%+

Boilers vs Heat Pumps: Typical Efficiency Comparison

  System   Energy In   Energy Out   Typical Efficiency
  Gas Boiler   1 unit   0.95 unit   Up to 95%
  Air source Heat Pump   1 unit   2.5-3.5 units   250-350%
  Ground Source Heat Pump   1 unit   3.5-4.5 units   350-450%

Why heat pumps need low temperature heating

Heat pumps use electricity while most boilers generally use gas. In the UK electricity is 3 – 4 times more expensive than gas in the UK. If you have not considered optimising your heating system and emitters, you might end up with a heat pump running at close to the same efficiency as your previous boiler, but at 3 – 4 times the cost.

Most UK home’s existing radiators are not ideal for use with heat pumps (and they aren’t the most efficient way to heat your home full stop). They require higher water temperatures to heat a room (typically sized for between 60°C and 75°C water). These heat emitters force your heat pump to work at high temperature and low efficiency, even nearing a 1:1 COP, causing high energy bills.

In contrast, underfloor heating systems such as a Wundafloor system operate at low temperatures, maximising a heat pump’s efficiency. Perfectly complementing the way heat pumps are designed to work, and providing consistent, comfortable warmth throughout your home.

More can be found in our article Heat Pump Flor Temperature Explained,

Why Underfloor Heating works so well with heat pumps

If you’re planning to install a heat pump at home, choosing the right heating system is crucial for comfort, efficiency, and savings.

The larger surface area of a Wundafloor system compared to traditional radiators allows for much lower temperatures to be used and generated by the heat pump. And, more effective and even heat emission across the entire room. Thanks to the aluminium layer of the Rapid Response® boards, heat is transferred quickly from the pipes to the floor surface, providing faster warm-up times and improved comfort.

Faster heat transfer and lower thermal resistance allow the system to respond more quickly to temperature changes, improving controllability and comfort. Also allowing you to use your heat pump in a more convenient and efficient manner. With operating temperatures of between 30°C and 45°C, heat pumps can operate at their most efficient performance.  Maximising energy savings and reduces running costs.

Compatible with all heat sources and the ability to install without digging up your floor, makes a Wundafloor a reliable and future-ready solution for both new builds and retrofit projects.

Find out more about underfloor heating 

Why Is My Boiler Making A Loud Vibrating Noise?

Heat Pump and Boiler Efficiency Explained

Lower water temperatures require much less energy to be used by it’s heat source. Since April 2005, UK homes have been required to use condensing boilers designed to run very efficiently up to 55°C. However, most still operate inefficiently because traditional radiators need 70–80°C, preventing the boiler from condensing. The comparison below shows how the choice between existing radiators vs. water-based Underfloor heating impacts heat source efficiency.

More can be found on comparing underfloor heating and radiators in this article comparing underfloor heating and radiators in this article

System Type Typical Flow Temp Boiler Condensing Typical Boiler Efficiency Typical Heat Pump COP Range
Existing Radiators 70–80°C Rarely 70-85% Up to 200%
Wundafloor Rapid Response 30–40°C Always 92-97% 300-600%

How to Maximise Heat Pump Efficiency

A heat pump is only as efficient as the system around it. The biggest factors affecting performance are your home’s insulation, heating emitters, and electricity tariff.

Fabric First Approach

Heat pumps work best in well-insulated homes that retain heat efficiently. Improving loft, wall, and floor insulation, while reducing draughts also lowers heat loss, reduces running costs, and helps maintain a higher COP.

Low Temperature Heating

Most UK radiators were designed for high water temperatures of 70–80°C. Heat pumps operate most efficiently at much lower temperatures, typically between 30–55°C. If flow temperatures are too high, efficiency drops significantly. Low-temperature heat emitters such as underfloor heating systems like a Rapid Response Wundafloor are often the ideal solution, allowing heat pumps to operate more efficiently while improving comfort and controllability.

Electricity Tariff (Running Costs Management)

Electricity prices in the United Kingdom are currently very high. Since a heat pump is powered by electricity, you need to manage this input cost or be at risk of the efficiency being cancelled out. Be sure to use an energy provider that can supply a beneficial flexible or time-of-use electricity tariff (such as Octopus Energy’s Cosy Tariff). These tariffs offer cheaper rates at times of low demand (e.g., overnight), allowing you to run the heat pump and heat your home/hot water when the electricity is cheapest, helping you control your running costs.

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Your Heat Pump Questions Answered

Heat emitters directly affect the flow temperature required by the system. Larger, low-temperature emitters such as underfloor heating allow heat pumps to operate more efficiently than traditional high-temperature radiators.

Yes, although older homes may benefit from insulation improvements and correctly sized low-temperature heat emitters to help maximise efficiency and comfort.

Heat pumps operate most efficiently when producing lower water temperatures. High-temperature heating systems force the heat pump to work harder, reducing efficiency and increasing electricity consumption.

Yes. Modern low-profile underfloor heating systems such as a Wundafloor can often be installed over existing subfloors without major excavation, making them suitable for many retrofit projects.

Most heat pumps operate most efficiently at flow temperatures between 30°C and 55°C. Lower flow temperatures generally improve efficiency and help achieve a higher Seasonal Coefficient of Performance (SCOP).

Underfloor heating is often considered the most effective heat emitter for heat pumps when possible to fit and use, because it can operate efficiently at lower water temperatures while providing even heat distribution and improved comfort. Systems like Wunda’s Rapid Response have the added benefit of being easy to control and use with quick heat up times.

Yes, but radiator performance depends on size and flow temperature. Most older radiators were designed for high-temperature boilers, whereas heat pumps operate most efficiently at lower temperatures. Some homes may require larger or additional radiators to achieve good performance.

Around 15–20 years with minimal maintenance.

Air source is the most common in the UK. Ground and water source are more efficient but require outdoor space.

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