When you’re planning an underfloor heating project, one of the first questions you’ll want answered is cost. It’s not just the cable itself that matters, but the whole system—the accessories that make it work and the installation that brings it together. With ThermoSphere’s Ultimate® heating cable, you’re not just buying any electric heating solution. You’re investing in advanced technology designed to simplify installation, reduce risk and deliver long-term performance. When paired with ThermoSphere Membrane, it becomes a true power couple: a system purpose-built to work in harmony, saving time and money on site while delivering reliable warmth underfoot.
Ultimate heating cables are supplied in reels, ranging from around 12m to over 200m, giving you flexibility to cover small bathrooms through to large open-plan spaces. When paired with ThermoSphere Membrane, the two products form a complete heating and decoupling system that’s fast to install and built to last.
Per m² (cable only): £55 – £75
Small bathrooms (3–4m²): £175 – £250 for cable
Medium kitchens (6–8m²): £360-£440 for cable
Large lounges/open-plan spaces (10–15m²): £600 – £850 for cable
ThermoSphere Membrane: around £20 – £25 per m²
Pro tip: Of course we recommend that you pair ThermoSphere Ultimate® heating cable with ThermoSphere Membrane mat, but our cable actually fits in any popular decoupling mat on the market. Our in line hot-to-cold joint makes it a snug fit in whichever mat is your preference.
*all prices are Inc. VAT and correct at the time of publishing, derived from the ThermoSphere price guide unless otherwise stated
Designed as a duo, the two products slot together seamlessly, creating a system that’s faster and easier to install than traditional loose wire methods. The membrane not only protects the cable and locks it in place, but also provides exceptional crack isolation for tiled floors, reducing the risk of movement damage over time.
A premium TwistedTwin heating cable designed to lock neatly into the ThermoSphere Membrane for fast, secure installation
A unique in-line hot-to-cold joint that removes bulky lumps, cutting into the membrane and removes weak spots
Lifetime warranty on the cable (when installed with a compatible ThermoSphere thermostat, sensor and registered correctly with us)
Full safety certifications to UK and EU standards
This isn’t just a heating cable; it’s part of a system created to make underfloor heating easy to install and built to last.
However, there are some things that aren’t included in the initial cost, but are highly recommended for the best results. They’re separate products, but when combined with Ultimate they complete the system and deliver maximum comfort and efficiency.
What’s not included, but almost always needed:
Decoupling membrane: £20–£25 per m²
or ThermoSphere Membrane: £20–£25 per m² (the perfect partner for Ultimate at no extra cost!)
Thermostat: £100–£200 depending on type (options include T-MO, BT21 and Dual Control)
Insulation boards: £11–£16 per m² depending on thickness and material
Flexible tile adhesive or levelling compound: £10–£20 per bag
Skipping these extras might trim the upfront budget, but it risks lowering performance and efficiency. For the best results, and to make the most of your Ultimate heating cable, we strongly recommend installing it as part of the complete ThermoSphere system.
If you’d rather have the whole project completed by professionals, labour rates vary depending on room size and complexity, but a full professional install often costs £60-£85 per m² according to Checkatrade.com. The good news is that using Ultimate with the ThermoSphere Membrane can actually shorten installation time. The cable clicks neatly into the membrane, with no chasing joints or fiddling to hold it in place, which means installers can work faster and with fewer complications.
When weighing up ThermoSphere Ultimate, it helps to see how it stacks up against other common underfloor heating options. Here’s a quick comparison:
Typical cost: £40–£60 per m² (kit only)
Installed cost: Around £40–£90 per m²
Best for: Floating timber, laminate or engineered wood floors where low build height is critical
Takeaway: Similar upfront price to mesh mats, but generally used in fewer settings
Typical cost: £35–£55 per m² (kit only)
Installed cost: £40–£90 per m²
Best for: Simple layouts in small to medium-sized rooms where speed of installation is the priority
Takeaway: A lower-cost option upfront compared to Ultimate & Membrane, but less flexible around fixed furniture or complex room shapes.
Typical cost: £85–£190 per m² installed (depending on new-build vs retrofit)
Best for: Whole-house heating, especially in new builds or large open-plan spaces
Takeaway: More expensive upfront than electric, but cheaper to run in the long term, especially when paired with renewable heat sources like heat pumps
ThermoSphere Ultimate® heating cable (approx. 4m² coverage at 130W/m²): £200–£250
ThermoSphere Membrane (4m²): £80–£100
Smart Thermostat: £100–£200
Insulation Boards (4m²): £50–£100
Adhesives & Levelling Compound: £30–£50
Electrician sign-off: £50–£150
Total DIY (with electrician): £450–£850
Total Professional Install: £700–£1,250
Homeowners often focus on the reliability and day-to-day comfort. One reviewer, who installed the system as part of a detailed property renovation, explained: “Having now completed the refurbishment of my bathroom and used my underfloor heating, I can say that it is certainly worth it. It is very easy to use and programme and the heat the floor gives off definitely heats the room.” For them, features like TwistedTwin construction and the in-line hot-cold joint added confidence that the system was designed to last.
Installers tend to highlight ease of fitting. Several reviews mention how much time is saved because the cable locks straight into the Membrane without fuss. As one installer put it: “Us installers love this product as the cable and membrane are very easy to work with.” The absence of a bulky joint is a small but important detail here, making installations smoother and reducing the likelihood of issues later.
Trade customers often point to the consistent support behind the products. One long-standing partner described ThermoSphere as “one of the best companies I have worked with… always polite on the phone, always willing to help. I would recommend them to anyone with total confidence.” For many in the trade, that backup is as valuable as the products themselves, because it helps projects run to plan.
So, how much does a ThermoSphere Ultimate® underfloor heating system cost?
Product price (cable + membrane): £75–£85 per m² (including materials and labour, new build)
Total installed cost (bathroom, 4m²): £500–£1,250 depending on DIY vs professional installation
Value: A flexible heating solution with smart design features (TwistedTwin, in-line hot-cold joint) paired with the security and speed of the Membrane system
Every project is different, and the exact price will depend on room size, floor finish and whether you choose to fit it yourself or hire a professional. The most reliable way to budget is to request a tailored quote for your specific room layout. That way, you’ll know exactly where you stand and you can look forward to stepping onto a perfectly warm floor.
*all prices are Inc. VAT and correct at the time of publishing, derived from the ThermoSphere price guide unless otherwise stated
Electric heating made easy
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