Is underfloor heating better with a heat pump?

Heat pumps can work with radiators or underfloor heating, and some types can work without either¹. Underfloor heating is often installed in combination with a heat pump and works with all types of heating systems². The choice between the two emitters is not about whether a heat pump will function, but about how efficiently it will run and what the installation will cost.

The core principle is flow temperature. Underfloor heating typically runs at around 35°C compared with 55 to 65°C or higher for radiators³. With underfloor heating, the flow temperature can be lower than with radiators, and this should result in the heat pump running much more efficiently⁴. Independent guidance puts the efficiency gain at 40% more efficient when running from a heat pump⁵, while one maker states underfloor heating is 45% more efficient than radiators when paired with heat pumps⁶.

Radiators are not ruled out. Existing radiators may need upgrading or resizing, and underfloor heating systems work particularly well with heat pumps because they provide consistent warmth at lower temperatures⁷. One case study puts it plainly: you do not need underfloor heating with a heat pump, but you might need larger radiators and some new pipework⁸.

Why heat pumps favour low flow temperatures

A heat pump's efficiency depends heavily on the temperature it has to produce. The lower the flow temperature, the less work the compressor does, and the better the coefficient of performance. This is why emitter choice matters more with a heat pump than with a gas boiler.

Underfloor heating has a much larger surface area than radiators, so it can heat a home at lower boiler or heat pump flow temperatures, saving money on energy bills⁴. Independent guidance gives a typical underfloor flow temperature of around 35°C compared with 55 to 65°C or even higher for radiators³. The Centre for Alternative Technology puts underfloor heating at a flow temperature of 35°C to 40°C¹⁰. One source gives the flow temperature of underfloor heating as around 45°C¹¹.

Heat pumps themselves are designed around these lower temperatures. Air-to-water heat pumps typically send hot water to radiators at a lower temperature than an equivalent fossil fuel central heating system, often between 35 and 45°C¹². Independent guidance describes sizing a system to supply flow temperatures of only 40 to 45 degrees to radiators when it is minus 3 degrees outside¹⁰. A maker states that heat pumps supply hot water at a lower flow temperature, typically 40°C to 45°C, than a boiler⁶. Underfloor heating runs lower still, typically 35°C compared with 55-65°C or higher for radiators⁹.

Ground source heat pumps produce heat at a lower temperature than other forms of heating and work best with underfloor heating, which requires lower flow temperatures than radiators¹³. The same principle applies across heat pump types: the emitter must be able to deliver the required heat output at the temperature the heat pump can economically produce.

For a household, this translates into a straightforward trade-off. Underfloor heating unlocks the lowest flow temperatures and therefore the best running efficiency, but it requires either new build or significant floor work. Radiators can work, but they may need to be larger, and the heat pump will run at a higher flow temperature to compensate, which reduces efficiency. The radiators and emitters page covers the sizing detail.

Efficiency: up to 40% more efficient when underfloor heating is paired with a heat pump

The efficiency case for underfloor heating with a heat pump rests on two independent figures and one maker claim. Independent guidance states that wet underfloor heating is 40% more efficient when running from a heat pump⁵. A maker states underfloor heating is 45% more efficient than radiators when paired with heat pumps⁶. The two figures differ, but both point in the same direction.

Water underfloor heating has higher efficiency than electric underfloor heating and radiators because the system runs at a lower temperature¹⁴. This is the mechanism behind the percentage gains: lower flow temperature means a higher seasonal performance factor for the heat pump.

The comparison is not only between underfloor and radiators, but between types of underfloor heating. Electric underfloor heating is generally more expensive than radiators to run because gas is cheaper than electric³. Water underfloor heating, by contrast, is generally always cheaper to heat a room with than radiators³. The running cost advantage belongs to water-based systems, not electric ones.

The efficiency gain is not automatic. It depends on the underfloor system being well designed and the home being well insulated. If you have a well-designed underfloor heating system and a well-insulated home, underfloor heating may be able to replace radiators efficiently¹⁵. Without those conditions, the theoretical gain does not materialise.

For a household's energy independence, the efficiency difference matters because it reduces the electricity the heat pump draws for the same heat output. A lower flow temperature means less imported electricity, which means less exposure to grid prices and supplier tariffs. The heat pump efficiency page explains how COP and SCOP are measured.

Wet or electric underfloor heating: which suits which home

Underfloor heating can be either a wet system that pumps warm water through pipes, or a dry system of electric coils under the floor¹⁶. The two have different cost profiles and suit different situations.

Electric underfloor heating tends to be cheaper than water underfloor heating to install, but has higher running costs¹⁵. It is more expensive than radiators both in terms of installation and running costs, with an exception for heating a single room where radiators cannot be zoned⁹. This makes electric underfloor heating a niche option: a bathroom, a kitchen extension, or a room where extending the wet circuit is impractical.

Wet underfloor heating is more expensive than radiators to install, but cheaper to run⁹. It is particularly suitable for new-build properties or when work is already being done on the floor¹⁶. For a heat pump installation, the wet system is the one that delivers the efficiency gain, because it can run at the low flow temperatures the heat pump produces.

A maker guidance note makes an important point for homes with both radiators and underfloor heating: connect each system independently to the boiler because radiators run at higher flow temperatures than underfloor heating⁶. This applies equally to a heat pump. Mixing the two on a single circuit without separation means the underfloor circuit receives water that is too hot, or the radiator circuit receives water that is too cool.

Independent guidance on heat pump suitability notes that heat pumps work best with underfloor heating, so this needs to be factored into the cost¹⁷. Having underfloor heating usually works well for heat pumps¹⁸. The decision between wet and electric is therefore not just about floor construction, but about whether the system will contribute to the heat pump's efficiency or simply provide local comfort.

Can existing radiators work with a heat pump, or do they need upgrading?

Existing radiators can work with a heat pump, but they often need to be larger. Independent guidance states that heat pumps benefit from the use of larger radiators or underfloor heating¹⁹. Possible upgrades include upgrading pipework, installing underfloor heating, or putting in larger radiators²⁰.

The reason is surface area. Bigger radiators have more surface area, which could mean using a double or triple panel radiator²¹. Radiators that were fine with a boiler at 75°C may not be big enough at 45°C²². You can get radiators that do not take up extra wall space, in the form of double or triple panel radiators²².

It is not mandatory to change radiators, but bigger radiators could hugely improve how well a heat pump can heat your home²¹. The decision depends on the heat loss calculation for each room and the flow temperature the heat pump is designed to run at. A well-insulated home with oversized existing radiators may need no changes at all. A poorly insulated home with small radiators will need upgrades.

Independent guidance also notes that more radiators are often needed or improved building insulation is required when a heat pump is installed in place of a liquid fuel or gas heating system²³. This is because heat pumps are most efficient when producing heat at lower temperatures than conventional boilers²³.

For a household, the practical question is whether the existing radiators can deliver the required heat output at the design flow temperature. If they cannot, the options are larger radiators, additional radiators, or a switch to underfloor heating where floor conditions allow. The do I need new radiators page covers the assessment in more detail.

Where underfloor heating falls short: retrofit cost, insulation and slow response

Underfloor heating is expensive and disruptive to retrofit, and is usually only a good option if significant building work is already being undertaken¹⁶. This is the single biggest limitation for existing homes. Lifting floors, laying insulation, installing pipework and pouring screed is a major project, and it is not compatible with occupied rooms.

Insulation is a prerequisite, not an optional extra. For the system to provide adequate heat and be cost-effective, it is critical to ensure the property is well insulated and draught-proofed¹⁶. When underfloor heating is the only source of heat in a room, insulation boards need to be installed beneath it to reduce the amount of heat being lost downwards³. The system should cover between 80% and 90% of the room's total floor area, wall to wall³.

In an old property with solid walls and few energy-saving measures, such as no loft insulation or single-glazed windows, it is unlikely that underfloor heating will be sufficient to heat a room on its own³. This is a firm limit, not a matter of system sizing. The heat loss from the fabric of the building exceeds what the floor can deliver at a safe surface temperature.

Response time is the other practical drawback. Underfloor heating takes between an hour and 90 minutes to heat a room, with electric underfloor heating slightly quicker than water³. Wet systems generally take much longer to heat up and cool down than traditional radiators, partly due to the screed or concrete in which most systems are embedded¹⁶. An underfloor heating system takes longer to heat a room, so it is vital to combine it with a timer²⁵.

This makes underfloor heating best left on a low temperature for a longer period, generally more suited to homes where people are in most of the day; if only used morning and evening, it alone may not provide sufficient warmth¹⁶. A household with a conventional on-and-off pattern may find radiators more responsive, even if they run at a higher flow temperature.

Floor coverings, furniture and floor surface temperature limits

The floor covering is part of the heating system, not a separate finish. Official guidance states that the overall design needs to take account of the thermal resistance of the floor covering, rather than setting a specific U-value, with third party guidance referenced²⁶. In practice, this means the floor build-up must be designed around the covering that will sit on top.

Tiles and stone are the best flooring for underfloor heating, because they conduct heat efficiently³. Most types of thin carpet, engineered wood, vinyl and laminate are compatible³. Thick carpet should not be used because it traps too much heat, and solid wood should not be used because it becomes warped by the temperature changes³.

Furniture placement is a real constraint. Underfloor heating systems can restrict what you can place on the floor, as they cannot sit under particular fittings and items of furniture¹⁶. A thick rug or a low sofa with a solid base acts as insulation, trapping heat in the floor and reducing the output into the room. This is the opposite of the radiator situation, where the advice is to keep radiators completely unblocked so they radiate their heat into rooms more easily²⁷.

For radiators, the maintenance advice is to keep them clear of clutter, because when a radiator is blocked by clothes and furniture, the warm air cannot circulate and the radiator works even harder to heat the room²⁸. Moving furniture away from radiators and turning radiators off in unused rooms are both suggested efficiency measures²⁹.

Underfloor heating systems rarely fail during normal working conditions, as they are safely encased by insulation, screed and flooring³. They are more likely to be damaged during installation than in day-to-day use³. Specialist engineers can pinpoint faults under a finished floor to within a few millimetres³. Some companies provide warranties and guarantees, and some offer lifetime guarantees or cover accidental damage as well as systemic failures³.

Comfort, control and what owning each system means day to day

Underfloor heating warms a home from the ground up by turning the floor into a large radiator². As the heat radiates from the floor, it enters the room evenly and provides a consistent temperature⁴. It transfers heat through both convection and radiation, helping to create a comfortable and constant temperature¹⁶. This even distribution is the main comfort argument for underfloor heating over radiators, which tend to create convection currents and warmer air near the ceiling.

Control is room by room. One case study describes having a thermostat in each room, which reduces the temperature overnight³¹. This level of zoning is possible with radiators too, using thermostatic valves, but underfloor heating lends itself to per-room control because each circuit can be regulated independently at the manifold.

Radiators require more routine attention. Checking radiators at least once a year to see if they need bleeding is standard advice³². Some sources suggest bleeding at least once a year, but preferably every few months³³. Others suggest about once a year, ideally before winter when the heating is used more regularly³⁴. One source suggests a couple of times a year, but checking before the cold hits²⁷. Bleeding radiators often removes air pockets and improves heating system efficiency²⁸.

If a radiator is hot at the top and cold at the bottom, it needs a power flush rather than bleeding³². To bleed a radiator, use a radiator key to open the small valve at the top and to the side slightly until water begins to drain out²⁹.

Underfloor heating has an effect on property value. It is an extremely desirable feature for home buyers, so a property including it will be worth more when sold¹⁶. This is a market observation rather than a guarantee, but it reflects the perceived comfort and efficiency benefits.

For energy independence, the picture is mixed. Underfloor heating paired with a heat pump reduces the electricity drawn per unit of heat, which reduces exposure to grid prices. But the household remains dependent on the electricity grid and a supplier, and on the heat pump manufacturer for parts and service. Underfloor heating itself has no moving parts and rarely fails, which reduces one category of dependence, but the heat pump and its controls remain the critical system. The heat pumps and energy independence page sets out the wider picture.