Pro tips for installing electric underfloor heating

Electric underfloor heating: a no-nonsense guide for first-timers, fixers and installers

Smart homeowners know that the best way to stay ahead of rising energy costs and winter chills is by planning smarter heating solutions, like electric underfloor heating. Whether you’re a professional installer branching out into electric systems or a weekend DIY warrior who’s just binge-watched 14 hours of YouTube flooring tutorials, you’re in the right place.

Before you get too cosy, this guide breaks down the essential things to know, the rookie mistakes to avoid and why underfloor heating might just become your new favourite tool in the box. It’s warm, it’s smart and done right, it’s ridiculously efficient.

Let us show you just how easy we make electric heating.

Tip 1                    Tip 2                    Tip 3                    Tip 4                    Tip 5                    Conclusion

Tip 1: Don't treat it like a radiator

Radiators blast hot air into a room and hope for the best. Electric underfloor heating works differently; it warms the floor itself and then gently radiates heat upwards. That means:

• No hot and cold spots
• Even warmth throughout
• Reduced energy waste from temperature overshoots

While radiators might run at 60–80°C (or 55°C in new builds) underfloor heating usually ticks along nicely at 21–23°C, keeping things toasty with much less effort. Want to run it even smarter? Set a setback temperature (around 16–18°C) when you’re not using the room.

Run it smart, not hot.

📱🌡️ How to programme your thermostat 🌡️📱

Tip 2: The electrics, know your load before you blow a fuse

This isn’t just plug-and-play. Electric underfloor heating can draw a fair bit of power, so make sure your circuit can handle it. Please ensure a qualified electrician carries out any electrical work. Every install is different, but here’s your cheat sheet:

• A 10A system should connect via a 16A thermostat and a 13A fused spur
• If your load is over 13A you’ll need a dedicated supply circuit from the distribution board
• The circuit needs RCD protection (minimum 30mA)
• If your system draws more than 16A and you still want a single thermostat, you’ll need a contactor snubber to switch the load safely

Here's a quick equation to check your system's demand:

Total wattage of your system in Watts / 230 Volts = Load in Amps

One of the easiest ways to overspend and underperform is skipping a heat loss calculation. Without it, you’re basically guessing how powerful your system needs to be and that can lead to:

• Sluggish heat-up times
• Rooms that never quite get warm
• Higher energy bills

Do the calculation, spec the right output and chances are you'll need less kit and less energy to stay warm. Good for your wallet and the planet.

💥🔌 When to install a contactor snubber 🔌💥

Tip 3: Planning, an electrician's best friend

Good installs start with good plans.
And no, sketching on the back of a napkin doesn’t count...

Here’s what to think about before rolling out anything:

• What’s the subfloor—concrete or timber?
• What kind of floor finish are you laying—tiles, wood, vinyl?
• How fast do you want the system to heat up?
• What’s the actual size of your heated area?
• What output do you need for the room to actually get warm?

Pro tip: get a heat loss calculation done. It’ll tell you exactly what’s needed to keep the room warm without wasting energy or over specifying. Smaller system, same results, lower bills. That’s smart heating.

Want the full checklist? We've got a deeper dive in our ‘What you need to know before installing electric underfloor heating’. But the main point here is measure twice, heat once.

💻📖 What you need to know before installing EUFH 📖💻

Tip 4: Test three times, you hat-trick hero

You know what’s worse than a cold floor? A cold floor that should be warm because the heating cable was damaged during install. So please don't skip this step, okay?

Here’s when to test:

1. Straight out of the box – make sure the cable wasn’t damaged in transit
2. After laying – check again before you pour leveller or lay tiles
3. After the floor’s finished – final sign-off before switching on

Most manufacturers (us included) require all three test results for your warranty to be valid. Think of it like MOTs for your underfloor heating.

📝📡 Testing your EUFH 📡📝

Tip 5: Common mistakes and how to dodge them, like a pro

Cutting the heating cable
Don't do it. Ever.

We know it’s tempting. You’ve got an extra bit of heating cable and nowhere for it to go, but heating cable works on a very precise resistance. Snip off “that little bit extra” and you’ve thrown the whole thing out of whack. Shorten the length and resistance drops, meaning you risk overheating, system failure and a voided warranty. Not ideal.

If you're registered with ThermoSphere CONNECT and you've made a mistake before the floor finish goes down, we’ll send a replacement. We even have engineers who can come out and assist on-site, warranty included.

❗⭕ Not registered? Why not? ⭕❗

Treating it like central heating
Electric UFH is not just plug-in radiators under tiles. It's best to only have it on when you need it. Sounds simple right? That's because it is! For example in a bathroom, you may only need it on for 2 hours in the morning and 2 in the evening. There wouldn’t be any point in having it on the whole time, because the heat up times can be as little as 15-20mins. It's the same reason as why you wouldn’t boil a kettle every 30 mins, 24/7, for having two cuppas a day.

Use a floor sensor and thermostat to maintain comfort without overdoing it. This setup is usually far more energy-efficient, especially in well-insulated spaces.

Going cheap and regretting it later
There are lots of “great deals” on UFH kits online, but let’s be honest; when your heating is embedded in your floor, you want it to last.

Look for:

• High-quality cable - TwistedTwin construction like ours is best
• Solid warranties that stick with the house
• A trusted brand that actually picks up the phone when something goes wrong

ThermoSphere’s warranty stays with the property so it’s great for resale value and even better for peace of mind.

Cutting corners on the install
We've seen it all: coils of unused cable stuffed behind bath panels, UFH systems wired straight into the mains, no thermostat, no floor sensor. You’re not saving time; you’re setting up a future headache and potentially a house fire.

Bottom line: don’t skip the instructions. If you get stuck, we've got how-to videos, install guides and real humans ready to help. Don’t risk it, do it right the first time.


Smart controls = smarter comfort
Once your system’s laid and tested, give it a thermostat that can do it justice.

We recommend pairing your electric UFH with the ThermoSphere Dual Control thermostat. Why? Because it lets you manage underfloor heating and towel bars independently, without needing separate control panels. It’s efficient, precise and lets you enjoy warm floors even when the rest of your heating’s off.

Control the warmth without burning energy when you don’t need to.

▶️⭕ Installing mesh underfloor heating ⭕▶️     ▶️⭕ Installing Ultimate underfloor heating ⭕▶️

Final thoughts: Good install, great results

Electric underfloor heating is one of the most efficient and comfortable ways to heat a space, but only if it’s done properly. With smart planning, solid testing and a good understanding of how the system works, you’ll get a result that looks invisible and feels incredible.

Plan ahead. Follow the steps. Avoid shortcuts. Test like your feet depend on it!

Need help with a project? Our team’s here for technical advice, product questions or to talk you out of cutting that heating cable. No scripts. No waffle. Just proper support from people who’ve been there.

Thinking of making the switch to electric UFH?
Give us a shout—ThermoSphere has your back (and your floor).

Electric heating made easy

🔥⚡ Check out our electric underfloor heating ⚡🔥

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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