What Size Underfloor Heating Kit Do I Need? (UK Guide 2026)
Choosing the right size underfloor heating kit is one of the most important steps when planning your system.
Too small, and your room won’t heat properly. Too large, and you risk wasted materials and unnecessary cost.
👉 The good news: it’s actually very simple once you know how to measure correctly.
• Measure your total floor area (m²)
• Subtract fixed furniture (baths, units, cabinets)
• Choose a kit slightly smaller than the total free space
• Most rooms → use 150W systems
Step 1: Measure Your Floor Area
Start by measuring the total size of your room in metres.
Example:
- Room length: 3m
- Room width: 2m
Total area = 6m²
This gives you your starting point.
Step 2: Subtract Fixed Areas
You should not install underfloor heating under permanent fixtures such as:
- Baths
- Toilets
- Kitchen cabinets
- Built-in furniture
Example:
- Total room = 6m²
- Bath + units = 2m²
Usable heating area = 4m²
👉 This is the number you use when choosing your kit.
Step 3: Choose the Right Kit Size
Always choose a kit that is slightly smaller than your available space.
This allows for spacing and easier installation.
- Available space: 4m²
- Recommended kit: 3.5–4m²
👉 Never try to force a larger kit into a smaller space.
Browse underfloor heating kits by size
What Wattage Should You Choose?
Once you know your size, the next step is choosing the right wattage.
- 150W systems: Best for most rooms
- 200W systems: For colder areas or high heat loss
👉 For most UK homes, 150W is the standard choice.
Example: Bathroom (8m²)
Room size: 8m²
Minus fixtures: 3m²
Heating area: 5m²
Recommended setup:
- 4.5–5m² heating kit
- 150W system
- Insulation boards
- Thermostat
This is a typical setup for a UK bathroom and will provide fast, even heat.
Why Insulation Boards Make a Big Difference
Insulation boards improve the performance of your system by reducing heat loss into the subfloor.
- Faster heat-up times
- Lower running costs
- Better efficiency
👉 Skipping insulation is one of the most common mistakes.
Heating Mat vs Heating Cable
The type of system you choose depends on your room layout.
- Mats: Best for simple, open areas
- Cable: Better for awkward shapes or small spaces
Both options are effective — it’s about choosing what fits your room best.
Common Mistakes to Avoid
- Buying a kit that is too large
- Forgetting to subtract fixed furniture
- Skipping insulation boards
- Choosing the wrong wattage
Not Sure What Size You Need?
Tell us your room size and layout, and we’ll recommend the exact kit for your space.
No guesswork — just the right setup.
👉 Get a free quote
👉 Speak to our team
Ready to Choose Your Kit?
Browse our full range of underfloor heating kits by size and find the perfect fit for your room.
