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150 W/m² versus 200 W/m² electric underfloor heating

Updated: 22 October 2026

You already measured the free floor and the listings still show two wattages per square metre. A 150 W versus 200 W electric underfloor heating choice is not about picking the bigger number. It is about heat loss, floor finish and what this amazon.co.uk set actually sells. Only one mat here is 150 W/m². Every other 230 V mesh mat states 200 W/m². Prices and stars are from the 19 October 2026 extract in our [electric underfloor heating comparison](/hub/heating/electric-underfloor-heating). Peter F. compared the listings on 20 October 2026. Nothing was tested in a lab. A qualifying purchase can earn a commission at no extra cost to you.

You already measured the free floor and the listings still show two wattages per square metre. A 150 W versus 200 W electric underfloor heating choice is not about picking the bigger number.

Our top picks

HEATIT HEATIT 5 m² mat with ET-84 thermostat

Best overall

HEATIT HEATIT 5 m² mat with ET-84 thermostat
7.4/10about £142.49
View offer
HEATIT HEATIT 2 m² mat with ET-81 thermostat

Rank 2

HEATIT HEATIT 2 m² mat with ET-81 thermostat
9.1/10about £99.99
View offer
HEATIT HEATIT 5 m² 150 W/m² mat

Alternative

HEATIT HEATIT 5 m² 150 W/m² mat
7.6/10about £46.54
View offer
On this page
  1. 1.What the two outputs are for
  2. 2.Bathrooms, conservatories and laminate are different cases
  3. 3.Insulation still matters at either output
  4. 4.The only 150 W/m² listing in this set

What the two outputs are for

Warmup’s StickyMat notes treat 150 W/m² as suitable for primary heat in a well-insulated area when boards reduce downward loss. They assign 200 W/m² to higher heat loss, such as a conservatory. BN Thermic uses the same split for tiled floors. Warmup also says a modern room might need on the order of 65 to 85 W/m² of heat, while a 150 to 200 W/m² system is specified because it cycles. That is duty-cycle logic, not a bill estimate. Neither output overrides a finish limit. Wood, laminate and linoleum should stay at or below 27 °C in Quick-Step’s UK FAQ, with no more than 0.15 m²K/W above the heating. A 200 W/m² mat under capped laminate still has to obey that cap through the thermostat.

Bathrooms, conservatories and laminate are different cases

Heat Mat steers small tiled bathrooms toward 200 W or 240 W/m² unless you only want to take the chill off the tiles. Warmup steers conservatories toward 200 W/m². Trade tables list bathrooms under both columns. That disagreement is on the bathroom electric underfloor heating page. A cold conservatory slab without boards is the classic 200 W/m² case. Well-insulated bedrooms appear in 150 W/m² examples. Laminate is a control problem as well as a wattage problem. One UK review of the 150 W/m² HEATIT mat under laminate made for underfloor heating reported barely warm floors. That is one review. Fastwarm’s claim of a twenty-five per cent faster warm-up at 200 W is their line for their own products, not a measured result for these listings.
HEATIT HEATIT 5 m² mat with ET-84 thermostat

Testsieger

HEATIT HEATIT 5 m² mat with ET-84 thermostat
7.4/10about £142.49
View offer

Insulation still matters at either output

No listing here includes insulation board. Heat Mat and BN Thermic describe boards as the way to stop heat sinking into a slab, and Warmup’s 150 W/m² notes assume boards on timber or concrete. Buying 200 W/m² without boards still spends electricity downward. Boards are an extra line, not part of the word kit. A sixteen-amp controller is roughly 3,600 W, about eighteen square metres at 200 W/m², as a rule of thumb. At 150 W/m² the same controller covers more area in theory. Do not invent a second figure without the electrician’s load calculation. YeloDeer’s 10.43 A line is for planning. Its 230 watt fragment is not a clean example of either output.

The only 150 W/m² listing in this set

The HEATIT five-square-metre mat is the sole 150 W/m² row: 750 W, 3.3 A, £46.54, thermostat not stated, 4.2 from five reviews. The 200 W/m² kit with ET-84 at £142.49 is 1000 W and 4.3 A, with a thermostat in the box and one rating. Same area, 750 W versus 1000 W. The gap is watts plus controller. Choose 150 W/m² when the room is well insulated and you will buy a floor probe separately. Choose 200 W/m² when loss is higher or the mat that fits is already 200 W/m². Five square metres plus a thermostat in one delivery means the 200 W kit. Smaller rolls are 200 W/m² only: the ET-81 kit is 400 W, and the three-square-metre minimat is 600 W.

Common questions

Is 150 W/m² enough?
It can be, in a well-insulated room with a conductive finish and proper downward insulation, according to Warmup and BN Thermic. It is not automatically enough under every laminate or every bathroom layout. This set has only one 150 W/m² mat, and one UK review under laminate reported barely warm floors.
When is 200 W/m² the better fit?
When heat loss is high, when you want a faster warm-up, or when manufacturer guidance for small tiled bathrooms points to the higher output. Weigh that against the actual floor build-up. A cold unboarded slab is a reason to look at insulation as well as watts.
Which is better in a bathroom?
UK guides disagree. Heat Mat favours 200 W/m² or more for small tiled bathrooms unless you only take the chill off the tiles. Warmup’s 150 W/m² line targets well-insulated rooms generally. This page does not declare one winner for every bath.
Does 200 W/m² cost more to run?
A higher output draws more power when the thermostat calls for heat, but duty cycle matters. Warmup describes 150 to 200 W/m² systems as cycling rather than running flat out. Do not calculate a yearly bill from the headline wattage. Fix the floor limit and the insulation first.
Will a higher output overheat laminate?
It can, if the control is wrong. Quick-Step’s 27 °C cap applies whether the mat is 150 W/m² or 200 W/m². A floor probe matters more than the headline wattage, because the thermostat is what holds the contact temperature.
Which captured mat is 150 W/m²?
The HEATIT five-square-metre mat at 150 W/m², 750 W, about £46.54 in the 19 October 2026 capture. No other 230 V row in this set uses 150 W/m². The thermostat is not stated on that listing.
Do I still need insulation if I buy 200 W/m²?
Yes, if the slab is cold and unboarded. Heat Mat and BN Thermic treat insulation boards as the way to stop heat going into concrete. Higher output is not a substitute for sending heat downward. None of these boxes includes a board.

Related pages

Electric underfloor heating buying guide

Best electric underfloor heating

Electric underfloor heating

Electric underfloor heating in a small UK bathroom

How to install an electric underfloor heating mat safely

Sources

Public UK sources named below. amazon.co.uk prices, stars and review counts on these nine listings were taken from the listing files captured on 19 October 2026. Page updated October 2026.

  1. Approved Document P (2013) (retrieved 20 October 2026)
  2. IET Part P FAQ (retrieved 20 October 2026)
  3. Professional Electrician, heating cables (retrieved 20 October 2026)
  4. Voltimum, electric floor heating (retrieved 20 October 2026)
  5. Warmup StickyMat (retrieved 20 October 2026)
  6. BN Thermic, tiles (retrieved 20 October 2026)
  7. Heat Mat, measuring up (retrieved 20 October 2026)
  8. Quick-Step UK laminate FAQ (retrieved 20 October 2026)