How Much Energy Does Underfloor Heating Use - And Will It Actually Hurt Your Bills?

A customer called us last year absolutely convinced that underfloor heating had tripled her electricity bill - she'd had electric UFH installed under a new kitchen extension, around 14m², and her bills had jumped in a way she couldn't ignore. When we actually looked at her setup, the thermostat was cranked to 28°C, running 10 hours a day, with zero insulation underneath the floor. The system wasn't the problem. The decisions were. And honestly, this comes up on almost every single project we work on at Eco Friendly Heating. So let's get into the actual numbers.

The Real Numbers: What Electric UFH Actually Draws

Electric underfloor heating typically runs at 100–200W per square metre, and a well-insulated 15m² room with a 150W/m² mat uses roughly 2.25kW at full load - at the UK average rate of around 24p/kWh in 2026, that's about 54p per hour when it's going flat out. But here's what most people miss completely: a properly set-up system doesn't run at full load all day. With a decent programmable thermostat and proper floor insulation underneath, that same 15m² system might only actively heat for 3–4 hours across a full day. That brings your daily cost to roughly £1.60–£2.20, which works out to around £48–£66 a month for that one room. Not nothing.

But not the horror story either.

Compare that to a badly set-up system running 8 hours a day at full load - you're looking at £3.50+ daily, nearly £110 a month for a single room. Same hardware. Very different outcome.

The Decisions That Actually Determine Your Bill

OK so this is where it gets practical, and honestly this is the part I actually get excited about because the gap between a cheap-to-run system and an expensive one isn't the technology, it's four pretty fixable decisions.

• Insulation beneath the heating element - Without it, you're heating the subfloor and structural concrete, not the actual room you're sitting in. We've seen heat-up times drop from 90 minutes to under 30 just by adding 6mm decoupling insulation boards, which is wild when you think about how cheap those boards are relative to the running costs.
• Thermostat quality and programming - A basic on/off thermostat versus a smart thermostat with floor and air sensors can cut runtime by 30–40%. Not an exaggeration, we've measured it.
• Floor covering - Thick carpet over UFH is like putting a duvet over a radiator. Stone, tile, or luxury vinyl with a low tog rating transfers heat well. Carpet above 1.5 tog will frustrate you every single month.
• Room usage patterns - UFH works best when it's maintaining temperature, not dragging itself up from cold over and over again. Frequent on/off cycles from cold are the most expensive way to run it, full stop.

This is where most people get it wrong, tbh - they buy a decent system and then undo it with a £15 thermostat and no insulation board. It drives me mad when I see it because the fix is usually under £200 and nobody told them.

Decision Debrief: Recommending Wet vs. Electric UFH for a Renovation Client

A client came to us mid-renovation - 1930s semi, ground floor only, concrete subfloor, 45m² total. The budget was tight, around £3,000 for the heating element and controls, and they wanted to know whether to go electric mat or wet (hydronic) UFH connected to their existing combi boiler.

We went electric.

And it wasn't just about the upfront cost - let me back up and explain why. Their combi boiler was a mid-range unit, no buffer capacity, already slightly undersized for the house. Adding 45m² of wet UFH would've meant either a boiler upgrade (another £1,500–£2,000 on top) or just accepting sluggish, underwhelming performance forever. So wet UFH was out.

The bit that surprised even us: we split the electric mats into two zones - kitchen/diner and hallway separately — with independent smart thermostats on each. The client now runs the hallway zone only in the morning, kitchen/diner in the evening. Monthly running cost came in at £55–£70 across winter. They were bracing themselves for £120+. Eco Friendly Heating Systems UK now defaults to zoned control on any electric UFH job over 20m². Single-zone installs on larger areas are genuinely where bills spiral - I've seen it happen too many times to pretend it's an edge case.

Hot take: most UFH installers don't push zoning hard enough because it adds a bit of complexity to the job. But for the customer it's the single biggest lever on running costs. Someone should say that more clearly.

Will It Actually Increase Your Bills?

Honestly - it depends entirely on what you're replacing. If you're swapping out portable heaters or infrared heaters running at 2–3kW per room anyway, UFH often comes in cheaper or roughly equivalent. If you're adding heating to a space that was previously unheated, yes, your bills will go up - but the real question is whether the system's been set up to keep that increase as small as possible. Everyone says UFH is expensive to run, but honestly it's more like... badly installed UFH is expensive to run. No insulation, cheap thermostat, high setpoints, no zoning - fix those four things and the whole energy story changes. The hardware itself isn't the villain here. I'm still not 100% sold on the idea that UFH is always the right call for every room, especially in older properties with dodgy subfloors and no budget for proper prep work, but when the conditions are right.

Frequently Asked Questions

Is electric underfloor heating cheaper to run than radiators?

It can be, especially in well-insulated rooms. So here's the actual mechanism - electric UFH heats at floor level, which means you feel warm at lower air temperatures, which means the thermostat cuts out sooner. Does that always beat radiators? No. It depends heavily on your current setup and how well the room holds heat.

How long does underfloor heating take to heat up?

With good insulation boards underneath, you're typically looking at 20–40 minutes to reach target temperature. Without insulation? More like 60–90 minutes, and a lot of wasted energy going down into the concrete rather than up into the room.

Can I run underfloor heating all day without it costing a fortune?

Only if your thermostat is genuinely doing its job (and a cheap one probably isn't). A smart thermostat maintains temperature rather than dragging the room back up from cold every few hours - that maintaining mode is far more efficient than repeated cold starts. Schedule it around when you're actually home.

Does underfloor heating work well with renewable energy?

Yes, and I personally think this is one of the strongest cases for electric UFH full stop. If you've got solar PV, you can programme the system to run during generation hours and let the thermal mass of the floor hold that heat for hours afterwards. At Eco Friendly Heating, from what I've seen, this combination works especially well with tiled floors in south-facing rooms. The floor basically becomes a slow-release heat battery.

What floor covering is most efficient over underfloor heating?

Porcelain tile or natural stone, low thermal resistance, holds heat well, releases it steadily. That's the gold standard. If you want carpet, keep the tog rating under 1.5 and use a purpose-made UFH underlay, otherwise you're basically insulating against the thing you paid to install.