The typical running cost of underfloor heating in the UK is between £450 and £700 per year for an average 70m² system, depending on your energy source and insulation levels (Energy Saving Trust, 2026). This figure assumes a well-insulated home and a thermostat set to 21°C for eight hours daily.
Your actual cost depends heavily on whether you use electric or water-based (wet) underfloor heating. Electric systems cost more per kWh to run but heat up faster, while wet systems are cheaper per kWh but require a boiler or heat pump. The biggest variable is your home’s insulation, poor insulation can double running costs regardless of system type (GOV.UK, 2026).
Electric underfloor heating running costs
Electric underfloor heating costs roughly 15p to 20p per kWh to run, based on the UK average electricity price of 24.5p per kWh (Ofgem, 2026). For a 10m² bathroom running four hours daily, this works out at about £1.50 per day or £45 per month. A full 70m² electric system used eight hours daily could cost £600–£1,000 annually. Electric mats are best for small rooms like bathrooms because they heat quickly and can be zoned separately.
Wet underfloor heating running costs
Wet underfloor heating running costs are lower per kWh, typically 6p to 10p per kWh when powered by a gas boiler (Energy Saving Trust, 2026). For a 70m² system, annual costs range from £350 to £550 with a condensing boiler. If paired with an air-source heat pump (COP 3.5), costs drop further to £200–£350 per year because the heat pump delivers three times more heat per kWh of electricity (GOV.UK, 2026). Wet systems cost less to run but more to install.
Key factors that lower your running costs
Insulation is the single most important factor. A floor with 50mm of rigid foam insulation can cut running costs by 30–40% compared to an uninsulated floor (BRE, 2026). Smart thermostats and room-by-room zoning also reduce waste, only heat occupied spaces. The Energy Saving Trust says underfloor heating runs at 35–45°C water temperature, versus 60–70°C for radiators. That makes it 15–25% more efficient with a heat pump (Energy Saving Trust, 2026). Always check your floor construction and insulation before choosing a system.
A worked example
A typical 70m² wet underfloor heating system in a 1930s semi-detached house in the Midlands costs roughly £280 per year to run when powered by an air source heat pump with good insulation. This scenario assumes a heat pump with a Seasonal Coefficient of Performance (SCOP) of 3.5, producing heat at 6p per kWh against the current electricity price of 24.5p per kWh from Ofgem. The homeowner uses the system for eight hours daily at 21°C across the ground floor. With the Boiler Upgrade Scheme grant of £7,500 covering most of the heat pump installation, the upfront cost of the underfloor heating system itself is around £3,500 for a new-build extension. Total annual savings compared to a gas boiler system running at 10p per kWh come to £180 per year, giving a payback period of roughly 19 years on the underfloor heating installation alone. Over 25 years, the total savings reach £4,500, not accounting for rising energy prices.
| Item | Figure |
|---|---|
| Upfront cost after grants | £3,500 |
| Yearly savings | £180 |
| Payback period | 19 years |
| 25-year lifetime savings | £4,500 |
What homeowners often get wrong
The most common mistake is assuming electric underfloor heating is always cheaper to run because it heats up faster. Three frequent errors lead to wasted money and missed savings.
- Ignoring insulation before installation Many homeowners install underfloor heating over an uninsulated concrete slab, thinking the system alone will keep the room warm. Without at least 75mm of PIR insulation board beneath the pipes or cables, heat escapes downwards and running costs can double to £1,400 per year for a 70m² electric system.
- Setting the thermostat too high People treat underfloor heating like radiators and set the thermostat to 25°C or higher for a quick warm-up. Underfloor heating works best at a steady 19°C to 21°C, and every extra degree adds roughly 8% to your annual running cost, which could mean an extra £56 per year on a wet system.
- Mixing system types in the same zone Some homeowners install electric mats in one room and a wet system in the next, then run both from the same thermostat. This confuses the control system and forces the electric mats to run longer than needed, potentially voiding the warranty on the wet system and adding £100 to £200 to yearly costs.
Quick reference
- Electric underfloor heating costs £600 to £1,000 per year for a 70m² system used eight hours daily at current UK electricity prices.
- Wet underfloor heating with a gas boiler costs £200 to £350 per year for the same 70m² area and usage pattern.
- You need at least 75mm of insulation below the underfloor heating to qualify for most ECO4 or BUS grant schemes and avoid heat loss.
- Using a heat pump with a SCOP of 3.5 cuts wet underfloor heating running costs to roughly 6p per kWh, saving £180 per year versus a gas boiler.
- Running underfloor heating on a constant low temperature rather than on-off cycles saves 10% to 15% annually, according to the Energy Saving Trust.
Frequently Asked Questions
For a 10m² bathroom used four hours daily, electric underfloor heating costs about £45 per month. A full 70m² wet system with a gas boiler costs roughly £30–£45 per month, according to Energy Saving Trust.
Yes, electric underfloor heating costs more per kWh (15p–20p) than wet systems (6p–10p). However, it heats up faster and works best for small rooms like bathrooms, as per Ofgem data.
It can add £600–£1,000 per year for a 70m² electric system used eight hours daily. But proper insulation and zoning reduce the impact, as advised by GOV.UK.
