Heating
Underfloor heating: electric or water?
Electric underfloor heating is cheap to fit and good for warming a small room quickly. Water-based systems cost more to install but are usually cheaper to run, especially with a heat pump.
Updated 2 October 2026 · energy.org.uk editorial team
The short answer
- Electric (dry) underfloor heating uses mats or cables under the floor. It suits small rooms that need warming quickly, such as bathrooms. Energy Saving Trust notes it is generally more expensive to run than a water system, and costly over long periods or large areas.
- Water (wet) underfloor heating runs warm water from a boiler or heat pump through pipes in the floor. Because it heats a large surface, it works at a lower water temperature than most radiators, which suits a heat pump well.
What running costs depend on
For an electric floor, the cost is the power drawn × the hours it is actually heating × your unit rate. A mat's rating (watts per square metre) is its maximum: once the floor is warm, the thermostat switches it off for part of the time. The underfloor heating calculator shows both the upper limit and an estimate that allows for the thermostat.
For a water system, the running cost is the cost of the heat from your boiler or heat pump. The heat pump calculator compares those running costs.
Check
What to check first
- The room size and use. A small bathroom used for short periods is where electric floors make most sense.
- Insulation under the floor. Without it, much of the heat goes down instead of into the room.
- Floor height. Water systems usually need more build-up than electric mats, which matters in a retrofit.
- Your heat source. Water underfloor heating with an old, high-temperature boiler set-up loses some of its advantage.
Do
Practical next steps
- Estimate the running cost of an electric floor in the underfloor heating calculator.
- For a whole floor or an extension, ask installers to quote for a water system and check it can run at a low flow temperature.
- Use a thermostat with a timer so the floor heats only when the room is used.
- Compare other ways to heat one room in the room heating calculator.
Take care
Important limitations
- Underfloor heating responds slowly, especially water systems in screed, so it suits rooms heated steadily rather than for short bursts.
- The calculator's mat rating is an example; check the label or manual for yours.
- Installation costs vary widely with the floor, so get quotes rather than relying on averages.