Short answer: Underfloor heating gives even heat from the whole floor at water temperatures of typically 35 to 45°C, frees up wall space and suits heat pumps, but costs more to fit and warms up more slowly in screed. Radiators are cheaper and quicker to fit in an existing home and respond faster, but at low water temperatures they lose much of their output: a radiator running at ΔT30 gives about 51% of its ΔT50 rating, and at ΔT25 about 40%. Many homes use both.
Underfloor heating and radiators both turn hot water into room heat. The difference is the size of the warm surface. A radiator is a small, hot panel on one wall. Underfloor heating is a large, gently warm surface across the whole room. That one difference explains almost everything else: water temperature, comfort, response time and how well each works with a heat pump.
This guide compares the two for UK homes. For the electric option, see water vs electric underfloor heating.
What is the difference between underfloor heating and radiators?
Underfloor heating heats a room from a large, low-temperature surface, while radiators heat it from a small, high-temperature panel. Here is how that plays out.
| Feature | Underfloor heating | Radiators |
|---|---|---|
| Warm surface | Whole floor | One or two panels |
| Surface temp | Max 29°C living areas | Much hotter |
| Typical water temp | 35 to 45°C | Rated at ΔT50 |
| Warm-up | Slower in screed | Fast |
| Wall space | All free | Panels on walls |
| Retrofit work | Floor up or overlay | Pipes and brackets |
| Heat pump fit | Very good | Often larger rads needed |
Under BS EN 1264, the floor surface of underfloor heating is limited to 29°C in occupied areas, 33°C in bathrooms and 35°C in edge zones. That cap is why underfloor heating feels gentle and why it needs a large area to do the job.
Which gives out more heat: underfloor heating or radiators?
A radiator gives more heat per square metre of surface, but underfloor heating has far more surface, so per room the two can match. A floor gives about 100W/m² when its surface is 9°C above the room, based on Danfoss data for BS EN 1264. A radiator's output depends on how much hotter its water is than the room, called ΔT (delta T).
Radiators in the UK are rated at ΔT50, a 70°C mean water temperature in a 20°C room. Run them cooler and output falls fast. Stelrad publishes these correction factors:
| ΔT (mean water minus room) | Share of ΔT50 output |
|---|---|
| 50 | 100% |
| 40 | 74.7% |
| 30 | 51.3% |
| 25 | 40.4% |
| 20 | 30.2% |
So a radiator sold as 1,000W gives about 404W at ΔT25. Underfloor heating has no such problem at low temperatures, because it is designed to run cool from the start.
Which is better with a heat pump?
Underfloor heating is usually the better match for a heat pump, because it heats rooms with water well below the 55°C maximum flow temperature that Approved Document L sets for new and replacement wet heating systems in England. Lower water temperatures make a heat pump more efficient.
Worked example: a 16m² living room losing 1,200W on a cold day.
- Underfloor heating: 1,200W ÷ 15m² of heated floor = 80W/m². That is within what a floor can give, at typically 35 to 45°C flow.
- Radiators on the same heat pump: say 50°C flow and 42°C return, a 46°C mean in a 21°C room. That is ΔT25, so radiators give 40.4% of their rating. You need 1,200 ÷ 0.404 = about 2,970W of radiator at ΔT50.
Nearly 3kW of radiator for a room that needs 1.2kW is a lot of wall. That is why the Energy Saving Trust says radiators upstairs will likely need to be larger when underfloor heating goes downstairs with a heat pump. Read more in underfloor heating with a heat pump.
Which heats up faster?
Radiators heat up faster. A radiator holds little water and starts warming the air within minutes. Underfloor heating in a screed floor takes hours to come up from cold, because it has to warm the screed first.
The trade-off is that a screed floor holds its heat. It suits rooms you heat steadily through the day, and it is run with steady temperatures and small setbacks rather than on and off. Low-profile overlay boards hold less mass, so they respond faster than screed. If you want quick heat for short periods, radiators or an electric mat under tiles respond better.
Which costs less to fit?
Radiators usually cost less to fit in an existing home, because the pipework is often already there and no floor work is needed. Underfloor heating needs boards or screed, insulation, a manifold and a pump pack, and in a finished room the floor must come up or be overlaid.
The gap narrows or vanishes when you are laying a new floor. In a new extension the insulation and screed go in anyway, so the extra is the pipe, panels, manifold and controls. Our underfloor heating cost guide prices this per m² with worked examples. If a heat pump means you would need much bigger radiators, include that cost on the radiator side too.
Which is cheaper to run?
With the same heat source, underfloor heating can cost less to run because it works at a lower water temperature, and the Energy Saving Trust notes that lower flow temperatures improve boiler and heat pump efficiency. The heat the room needs is set by its heat loss, not by the emitter, so the saving comes from efficiency, not from needing less heat.
| Emitter | Typical flow temp |
|---|---|
| UFH in screed | 35 to 45°C |
| UFH on overlay boards | Often 45 to 50°C |
| Radiators sized for heat pump | Up to 55°C |
| Standard radiators | Rated at ΔT50 |
The overlay figure follows one maker's guidance for low-profile panels. See our running costs guide for worked annual figures.
How do comfort and space compare?
Underfloor heating spreads heat evenly from the floor, while radiators create a warm zone near the panel and rely on air movement to reach the rest of the room. The Energy Saving Trust lists consistent temperatures, comfort underfoot and free wall space as benefits of underfloor heating, and notes that furniture and curtains are less likely to block it.
Radiators have their own practical points. A towel radiator dries towels. A radiator is easy to bleed, replace or move. And a radiator does not care what floor finish you choose, whereas underfloor heating works best under tile and stone and needs carpet and underlay kept to 2.5 tog or less.
Can I have underfloor heating and radiators together?
Yes. A common set-up is underfloor heating on the ground floor and radiators upstairs, all from one boiler or heat pump. How you connect them depends on the heat source.
- Gas or oil boiler: the boiler runs the radiators at its normal temperature. A blending valve pump pack at the manifold mixes the water down for the floor.
- Heat pump: design both at the same low flow temperature. Radiators are sized for it, and the floor runs through a non-mixing pump set.
- One room only: a single room mixing pump pack can run one underfloor loop straight off a radiator circuit, with no manifold.
- Controls: give each underfloor zone a room thermostat and actuator, wired through a wiring centre that also calls the boiler or heat pump.
How do I choose between underfloor heating and radiators?
Use underfloor heating where the floor is being laid anyway, where you have or plan a heat pump, and in open-plan or glazed rooms where wall space is short. Keep radiators where floors are finished and staying, in rooms you heat for short bursts, and where you need quick response. If a room's heat loss is above about 100W/m² of heated floor, plan a radiator or second heat source alongside the floor.
Products for this job
- UFH manifolds, 2 to 12 port
- Blending valve pump pack with Grundfos UPM3 Auto, £266 inc VAT, October 2026, for boiler systems
- UFH non-mixing pump set with Wilo 6m pump, £215, for heat pumps
- Single Room UFH Mixing Pump Pack, £231, to run one room off a radiator circuit
- Heatmiser UH8 8 zone wiring centre
- Heatmiser neoStat V3, £77 per zone
- Castellated panels for screed floors
Related guides: Is underfloor heating worth it?, Underfloor heating with a heat pump and Will underfloor heating heat my room?
Replacing radiators with underfloor heating? Design it free with MaxHeatUFH ProLoop. Add your rooms and floor type, and get a loop design and full kit list with prices. Start your design
Frequently asked questions
Is underfloor heating better than radiators?
It is better for comfort, wall space and heat pumps. Radiators are better for quick heat, low fitting cost in existing homes and easy servicing. The right answer often depends on whether the floor is being laid anyway.
Do I need bigger radiators with a heat pump?
Often, yes. At a ΔT of 25, a radiator gives about 40% of its rated ΔT50 output, so it may need to be around two and a half times larger. Underfloor heating avoids this because it is designed for low water temperatures.
Can underfloor heating replace all my radiators?
It can, if each room's heat loss is below what its heated floor can give, about 100W/m² at a 29°C surface. Rooms with high heat loss may still need a radiator.
Can I run underfloor heating and radiators off the same boiler?
Yes. The radiators run at boiler temperature, and a blending valve pump pack at the manifold mixes the water down for the floor.
Why does underfloor heating feel warmer at a lower thermostat setting?
Because the heat comes from the whole floor, the room has fewer cold spots and your feet are warm. Many people find they are comfortable at the lower end of the 18 to 21°C range the Energy Saving Trust suggests.
Is underfloor heating slower than radiators?
Yes, in screed. It is designed to run steadily rather than switch on and off. Overlay boards and electric mats under tiles respond faster.
What ΔT are radiators rated at?
UK radiator outputs are normally quoted at ΔT50, where the mean water temperature is 50°C above room temperature. Use a correction factor to find the output at lower temperatures.
Sources: Energy Saving Trust: underfloor heating, Energy Saving Trust: thermostats and heating controls, Stelrad: radiator correction factors, Danfoss: EN 1264 floor surface temperatures and heat output, BEAMA: Part L heating controls guidance, Polypipe: UFH for existing floors