Is Underfloor Heating Cheaper to Run Than Radiators?

The short answer

With a heat pump, underfloor heating is cheaper to run than radiators. With a gas or oil boiler, the difference is small and you are buying comfort rather than savings. Electric underfloor heating costs the most per unit of heat of any option, which is why it belongs in a bathroom rather than a whole house.

Why flow temperature is the whole argument

A floor is a huge emitter. Spread the same heat output over 20 m² of floor instead of 2 m² of radiator and you can deliver it with much cooler water — typically 35-40°C for underfloor heating against 45-55°C for correctly sized low-temperature radiators, and 65-75°C for the old radiators in most boiler-heated homes. Everything about running cost follows from that number.

With a heat pump

A heat pump's efficiency is a function of the gap between the outside air (or ground) and the water it has to produce. Ask for cooler water and the same electricity delivers more heat. That is why a heat pump feeding underfloor heating runs at a higher seasonal efficiency than the same heat pump feeding radiators in the same house — and why underfloor heating is usually specified with a heat pump in new build and deep retrofit.

The grant sits on the heat pump, not the floor: the Boiler Upgrade Scheme pays £7,500, or £9,000 until March 2027 where you are replacing oil or LPG and have no mains gas connection. Heat pump installations in homes are zero-rated for VAT until 31 March 2027.

With a gas or oil boiler

A condensing boiler does gain a little from lower return temperatures — that is what "condensing" means — but the gain is nothing like a heat pump's. Fitting underfloor heating to a boiler system is therefore a comfort and layout decision: even heat, no radiators on the walls, warm floors underfoot. Expect the fuel bill to be similar, not transformed.

Electric underfloor heating

An electric mat converts electricity to heat one-for-one. A heat pump multiplies it three or four times over. So per unit of delivered heat, electric underfloor heating is the most expensive way to warm a room in this article — fine for the 4 m² of a bathroom floor used for an hour a day, expensive as a whole-house strategy. It is also notifiable work: a new circuit, and any electrical work in a bathroom, must be certified under Part P of the Building Regulations.

What ruins the saving

• Deep setbacks. A screed floor has hours of thermal lag. Turning it off overnight and expecting warmth at 7am means overheating the water to catch up — the opposite of efficient.
• Aggressive zoning. Closing most loops leaves a heat pump with nowhere to send its output, so it cycles. Fewer, longer, gentler is cheaper.
• Thick carpet and underlay. They insulate the floor from the room. Tile and stone are the best conductors; check the maximum surface temperature for engineered timber.
• Missing insulation under the floor. Without it, a good share of your heat goes into the ground.

Which rooms are worth it

Whole ground floors in new builds, extensions and deep retrofits — especially with a heat pump. Kitchens and bathrooms, where the floor finish is already tile. Rooms where wall space is precious. What rarely pays is retrofitting a single bedroom upstairs into an otherwise radiator-based system.

For Cornwall-specific costs per m², floor build-ups by floor type and how we pair the two, see underfloor heating Cornwall, and heat pumps Cornwall for the heat source that makes the saving real.