Short answer: Choose an electric mat for square or rectangular rooms, because it is the fastest to lay and the cable spacing is fixed for you. Choose loose cable for L-shaped, small or awkward rooms, where a 0.5m wide mat leaves gaps, and when you want to set your own output by changing the spacing. For a 4m² floor at 150W/m², a mat costs £104 and 10W/m loose cable costs £107 plus about £57 of uncoupling membrane (inc VAT, October 2026).
Mats and loose cable use the same idea: a twin-core heating cable in the tile adhesive bed, connected through a single cold tail to a floor-sensing thermostat. The difference is how the cable is held at the right spacing. On a mat it is fixed to a mesh at the factory. With loose cable you set the spacing yourself, using the studs of an uncoupling membrane. This guide compares the two on cost, speed, coverage and output, with worked examples. For the full laying method, see how to install an electric underfloor heating mat.
What is the difference between an electric mat and loose cable?
A mat is heating cable pre-fixed to a self-adhesive 0.5m wide mesh at a set spacing, so the output per m² is fixed. Loose cable comes on a reel with no mesh, so you choose the spacing, and the spacing decides the output.
| Feature | Mat | Loose cable |
|---|---|---|
| Output | Fixed: 100, 150 or 200W/m² | Set by spacing |
| Best room shape | Square, rectangular | L-shaped, small, awkward |
| Laying speed | Fastest | Slower |
| Holds spacing | Mesh | Membrane studs |
| Sizes | 1 to 12m² | 5m to 160m lengths |
| Cut the cable? | Never | Never |
Both need a floor-sensing thermostat, a 30mA RCD and an electrician for the final connection.
Which is quicker to install?
A mat is quicker in a regular room: you roll out a 0.5m strip, cut the mesh at the wall, turn it and roll back. Loose cable takes longer because you press the cable between the membrane studs run by run.
The time gap closes in awkward rooms. A mat has to turn in 0.5m steps, so around a pedestal, a curved shower screen or a narrow return it either leaves bare floor or needs careful mesh cutting. Loose cable follows the shape at the same spacing all the way, so the whole free floor is heated evenly.
How do I set the output with loose cable?
You set the output by choosing the spacing between cable runs: closer runs give more watts per m². Output per m² is the cable's watts per metre divided by the spacing in metres.
| Floor output | 10W/m cable spacing | 20W/m cable spacing |
|---|---|---|
| 100W/m² | 100mm | 200mm |
| 130W/m² | 75mm | 150mm |
| 150W/m² | 65mm | 130mm |
The 10W/m cable laid close together gives the most even surface temperature in a thin tile bed. The 20W/m cable gives twice the output per metre, so you need half the length at wider spacing, and it can also be laid in a screed. The 10W/m cable is only for the tile bed over the membrane.
How do I size loose cable for a room?
Multiply the free floor area by the output you want, then choose the cable length whose wattage is closest to that figure. The cable can't be cut, so the length you buy must fit the heated area at your spacing.
- Measure the free floor area, leaving out baths, shower trays, units and the toilet.
- Multiply by your target output. For 4m² at 150W/m²: 4 x 150 = 600W.
- Pick the nearest cable: the 10W/m 60m cable is 600W.
- Check the spacing: area ÷ length = 4 ÷ 60 = 0.067m, so about 65mm.
- Plan the runs on paper first, so the cable ends at the cold tail with no spare.
With the 20W/m cable, the 30m length is 650W. At 4 ÷ 30 = 0.133m, that is about 130mm spacing and roughly 160W/m².
Which costs less: an electric mat or loose cable?
For a regular room, a mat usually costs less because it needs no membrane to hold the spacing. Loose cable needs the uncoupling membrane, which adds about £11 per m², so it is the dearer route unless the membrane was going in anyway, for example on a timber floor.
| 4m² at about 150W/m² | Heating | With membrane |
|---|---|---|
| Mat 150W/m², 4.0m² | £104 | £161 |
| 10W/m cable, 60m | £107 | £164 |
| 20W/m cable, 30m | £71 | £128 |
Prices inc VAT, October 2026. The membrane column adds the 1m x 5m roll at £57. On timber or new screed you should fit the membrane under a mat too, so the comparison is then much closer.
Worked example: an L-shaped en-suite
An en-suite is 2.2m x 2.0m (4.4m²) with a 0.9m x 0.9m shower tray in one corner and a toilet and basin pedestal taking about 0.5m². That leaves about 3.1m² of free floor, in an L shape around the tray.
- Mat: the 3.0m² mat fits the area on paper, but the L shape and the pedestal force several turns in 0.5m steps. Expect some unheated strips along the tray and around the pedestal.
- Loose cable: at 150W/m², 3.1 x 150 = 465W. The 10W/m 50m cable (500W) gives 3.1 ÷ 50 = 62mm spacing, or about 160W/m². The 40m cable (400W) gives 78mm spacing, or about 130W/m². Either fills the L shape right up to the tray.
Here loose cable is the better choice: £89 for the 50m cable or £71 for the 40m, plus the 1m x 5m membrane at £57.
Do mats and loose cable need the same thermostat?
Yes. Both need a floor-sensing thermostat that switches the load directly and limits the floor temperature. The Heatmiser neoStat-e and Slimline-E both switch up to 16A and include a floor sensor. At 230V, 16A is about 3.68kW, which covers most single rooms.
Don't use the Heatmiser RF-Switch 16A for floor heating. Heatmiser state it has no floor limiting sensor. For bigger rooms and multiple mats, see electric UFH thermostats and 16A loads.
Which should I choose?
Use this rule of thumb: if you can cover the free floor with 0.5m strips and few cuts, buy a mat. If you can't, buy loose cable.
- Mat: kitchens, utility rooms and bathrooms with a clear rectangle of floor; jobs where speed matters.
- 10W/m loose cable: en-suites, cloakrooms, L-shaped rooms, floors broken up by pedestals and trays.
- 20W/m loose cable: larger areas at wider spacing, or a cable laid in screed.
Running costs are the same for the same watts and hours, whichever you choose. See underfloor heating running costs for how to estimate them.
Products for this job
- Electric mat 150W/m²: 1 to 12m², from £41
- Electric mat 100W/m²: for low heat loss rooms, from £39
- Electric mat 200W/m²: for conservatories, from £41
- Loose heating cable, 10W/m or 20W/m: from £14
- Uncoupling membrane, 1m wide: 5m² £57, 10m² £113, 15m² £170
- Heatmiser neoStat-e: £83, or the Slimline-E at £56
Prices inc VAT, October 2026. Browse electric mats and electric loose cable.
Not sure which suits your room? Try MaxHeatUFH ProLoop. Add your rooms and floor type, and get a design and a full kit list with prices. Start your design
Frequently asked questions
Is loose cable better than a heating mat?
Not better, just more flexible. It heats the same way, but you can follow any room shape and set your own output. A mat is faster and usually cheaper in a regular room.
Can I cut electric underfloor heating cable to length?
No. Neither loose cable nor mat cable can be cut, shortened or joined. Choose a length that fits the free floor at your spacing.
What spacing should loose heating cable be?
It depends on the output you want. The 10W/m cable gives 150W/m² at 65mm and 100W/m² at 100mm. The 20W/m cable gives 150W/m² at 130mm and 100W/m² at 200mm.
Do I need a membrane for loose cable?
Yes. The uncoupling membrane's studs hold the cable at the right spacing, and the membrane also stops subfloor movement cracking the tiles.
Can I use two mats in one room?
Yes, if the total load stays within the thermostat's 16A rating. Each mat has its own cold tail, so your electrician will join them at the thermostat or in a connection box.
Can loose cable go in screed?
The 20W/m cable can be laid in a screed. The 10W/m cable is for the tile adhesive bed over the membrane.
Is a mat or loose cable cheaper to run?
Neither. Running cost depends on the watts, the hours on and your electricity price, not on whether the cable came on a mesh.
Sources: IET Wiring Matters: BS 7671 Section 753 floor heating, Heat Mat loose heating cable installation instructions