10 big underfloor heating myths and why they're wrong

If you’ve ever typed “Is electric underfloor heating worth it?” into a search bar and found yourself spiralling into forums full of half-baked opinions and horror stories from 2008… you're not alone.

There’s a lot of misinformation out there. So today we're clearing the air (and warming the floor) by busting some of the biggest myths around electric underfloor heating. Whether you’re installing it, specifying it or just curious, consider this your myth-busting crash course.

Because let’s face it, electric underfloor heating (EUFH) deserves better PR.

Jump straight to:

- It's too expensive?
- It only works under tiles?
- You can't do it yourself?
- It takes ages to heat up?
- It can't heat a whole room?
- It's not safe in bathrooms?
- It's only for new builds?
- It will add a massive step up to my room?
- You have to rip up the whole floor if there's any issues?
- It's a hassle to install?

Myth 1: Electric underfloor heating is crazy expensive to run

Well… it’s more efficient than you think.

Yes, electric heating uses electricity (shocker). But that doesn’t mean it’s a power guzzling monster. In fact, electric underfloor heating is zone controlled, meaning low temperature and high efficiency.

Because it heats the floor evenly and directly, there’s no wasted heat lingering at ceiling height. Plus, with smart thermostats and setback temperatures you only heat the space when you need it, no more paying to warm an empty room.

Bonus points if you add insulation boards, these can cut your running costs by up to half! Only use these if you want to save money and be efficient though...

"But my auntie's second cousin once removed had it and it made her electricity bill quadruple"

There’s always one. Someone somewhere who claims they needed a second mortgage because they left their underfloor heating on 24/7 at 30°C with the windows open and no insulation boards. Let’s be real: if you use it smartly, UFH won’t bankrupt you. Use a thermostat, set schedules and apply setback temperatures. It’s not magic, it’s just efficient design.

As a general rule of thumb, it costs about 2p per M² per hour. So if you’ve got a 3M² bathroom and you run it for
1 hour in the morning
2 hours in the evening
It will cost you 18p per day, or £5.40 per month. Which is about as much as a Costa double frappe latte with extra whipped cream and a cherry on top.

👍💰 Is it worth it? 💰👍    ✖️➗ Running cost calculator ✖️➗ 

Myth 2: It only works under tiles

Wrong again. While tiles are a popular choice because they conduct heat beautifully, electric underfloor heating (EUFH) can work under stone, wood, laminate, carpet and vinyl. All you need is the right system and installation build-up.

ThermoSphere's products cover all bases, with tailored advice depending on the floor finish. So, whether you're going for rustic wood in the kitchen or soft vinyl in the bedroom, we've got you covered (from underneath, of course).

❔❓ Which one is right for you? ❓❔

Myth 3: You can’t install it yourself

Now, we’re not saying everyone should, but plenty of DIYers take on EUFH installs. Electric underfloor heating is designed to be DIY-friendly, with a big asterisk. Laying the mats or cables, cutting them to shape without damaging them and applying adhesive or self-levelling compound can be done by a competent DIYer.

As long as you plan properly, follow the instructions and leave the final electrical connection to a Part P registered electrician, you’re golden. We’ve even got step-by-step install guides and videos to walk you through it. Just don’t wing it, planning is your best mate here.

And yes, you still need to do three resistance tests during install. No skipping. We’ll know.

🔌📝 How to test 📝🔌

Myth 4: It takes ages to heat up

Not with the right setup it doesn’t. Want quick warm-up times? Use insulation boards to reduce heat loss and get faster response. A well-installed EUFH system can heat a room in as little as 15–30 minutes, depending on insulation levels, floor build-up and the output you choose. It’s all about minimising downward heat and focusing energy where you actually want it… your feet. Add a smart thermostat and you can even pre-warm the floor before you step in the room. No waiting around in your towel.

The real differences:

Underfloor Heating:

• Improved efficiency and comfort
• Underfloor heating provides a comfortable, even temperature throughout your room.
• If the heating system is under the whole floor you can save money through lowering the ambient temperature by 2°C without loss of comfort!
• You can also free up valuable wall space creating more freedom of design for your interiors.

Radiators:

• Inefficient convection heating
• Traditional radiators distribute heat unevenly throughout a room, resulting in drafts, hot heads and cold feet.
• Heating this way usually means your thermostat has to be set to a higher temperature to achieve the desired comfort level, which increases heat loss and energy bills.

👌♨️ Want to make the most of it? ♨️👌

Myth 5: It’s not powerful enough to heat a whole room

The reality is that it can absolutely be your primary heat source.

Assuming your property is reasonably well insulated, electric underfloor heating can 100% be your main heating source, even in chilly parts of the UK.

Just make sure you:

• Get a heat loss calculation
• Choose the right output per m²
• Cover at least 80–90% of the floor area

As a quick rule of thumb, many new builds can be heated with as little as 35W/m². Our electric underfloor heating systems start from 100W/m² and go up to 200W/m², so they’re more than capable of heating your room. “Ok, so they’re over-powered and more expensive to run,” I hear you say. Actually, no—the output per square metre affects how quickly the system heats up, not the final temperature. The actual kilowatts of energy used stay the same across different outputs; it’s just delivered over a shorter or longer period of time.

Still not convinced? Think of it like this, would we sell underfloor heating if it only worked for one foot? Of course we wouldn't. When we sell you a product designed to heat your room, rest assured it will heat your room.

✔️📑 A quick 'how to' 📑✔️

Myth 6: It’s not safe in bathrooms

Electricity and water? We get the hesitation. But when installed properly, electric underfloor heating is made for bathrooms. That’s why systems come with proper insulation all IP-rated, tested to the highest safety standards and protected by RCDs.

In fact, ThermoSphere Mesh has an IP68 rating, which means it is safe even when fully submerged in water. You could wrap yourself in it and jump in a swimming pool. But, don’t.

Better still, they free up wall space by removing the need for radiators. If you add in our 12V towel bars, you’ve got a sleek, stylish heating solution that’s both safe and practical.

➖⚡ Check out our towel bars ⚡➖

Myth 7: It’s only for new builds

Nope. While new builds are an obvious win, retrofitting electric UFH is more common than you think. Thanks to ultra-thin cables and mats, the added floor height can be minimal, sometimes as little as 3–4 mm.  A layer of tile adhesive is usually about 6mm so the EUFH fits within that. That means you can install it over existing subfloors with minimal faff. If you're refurbishing a bathroom, kitchen or even just updating your flooring, it's the perfect time to future-proof your space with underfloor heating... without the need to tear up your entire subfloor!

🔎👀 A closer look 👀🔍

Myth 8: It will add a massive step up into my room

Similarly to myth 7, this one gets said a lot. But with our in line hot/cold joint Ultimate Cable or our mesh mats, the floor build-up can be minimal. ThermoSphere Mesh is 3.2mm thick, so basically gets lost in the tile adhesive with negligible floor build up. ThermoSphere membrane & Ultimate® heating cable is 5.5mm thick, but can often save height up to 25mm height build up because it combines the decoupling, waterproofing and underfloor heating all in one layer.

You’re looking at millimetres, not mountains and you won't need a step ladder to brush your teeth, we promise.

🔵📏 Ultimate cable 📏🔵

Myth 9: If it goes wrong, you have to rip up the whole floor

That would be a nightmare, but it’s not true. With proper testing (before, during and after install) faults are incredibly rare. But even if the worst happens, fault-finding equipment can pinpoint the exact location of damage and repair kits make patching up easy without lifting the whole floor.

ThermoSphere offers a lifetime warranty on its electric underfloor heating systems, including Mesh, Membrane, Foil, Screed Cable and the Ultimate cable (provided the system is registered within 60 days of installation). This warranty is property-linked, meaning it automatically transfers to new owners if the home is sold. ThermoSphere thermostats are covered by a separate three-year warranty, while the Ultimate cable also comes with a 12-month replacement guarantee that includes both the heating system and any damaged flooring if a manufacturing defect occurs after registration. To maintain coverage, all registration information must be accurate, as false or incomplete details can void the warranty.

🙂☎️ Need our help? ☎️🙂

Myth 10: It's a hassle to install

Electric heating made easy. That’s our slogan, we made it that for a reason. Our electric underfloor heating system is designed to be straightforward and hassle-free. Our mesh system has self-adhesive backing, which allows for quick placement and secure fixing without the need for additional adhesives or tools. Our ThermoSphere Ultimate Cable incorporates TwistedTwin construction and in-line joint technology, meaning it’s uniform in thickness from end to cold tail and completely eliminates bulky hot/cold joints, there’s no need to cut into the membrane, substrate or floor which significantly reduces installation risk and difficulty. It’s compatible with all decoupling membrane mats, making it adaptable to installers’ preferred systems Plus, we back it up with step-by-step guides available on our website and comprehensive YouTube videos to walk you through every phase of installation, from preparation to tiling, ensuring confidence, clarity and a seamless experience for all installers.

▶️📽️ Youtube 📽️▶️

Final thought

So there you have it. The myths are officially debunked, the facts are out and electric underfloor heating is standing strong in the face of misinformation. Electric underfloor heating isn’t some mysterious luxury reserved for the rich or reckless, it’s smart, safe and incredibly efficient when done properly. So let’s put these old myths to bed and start treating UFH like the modern heating solution it is.

Whether you’re a seasoned installer, a curious homeowner or someone whose aunt’s cousin has opinions, now you know the truth.

Still not sure? Ask us. No myth, no mystery, just warm happy floors.

❔📕 Is it right for you? 📕❔

Electric heating made easy

Questions?

Or contact us via the website, or give one of the team a call on 01622 689440. Find out more about ThermoSphere by reading of one of our other blogs here.

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