Why Wunda Rapid Response® Overfloor Heating Costs Less to Run

  • Optimising heat source performance – Low flow temperature heating compatible
  • Cosy rooms in 30 minutes.
  • Unbeatable comfort with the lowest running costs.
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All comparisons are based on Ofgem’s typical UK household heat use of 11,500 kWh per year

To make a fair and transparent comparison, the figures shown in this page assume a typical mid-range UK household heat requirement using Ofgem’s Typical Domestic Consumption Values (TDCVs). Ofgem estimates that a medium household (2–3 bedroom home, 2–3 occupants) uses around 11,500 kWh per year for space heating.

Throughout this page, 11,500 kWh per year is treated as the heat delivered to the home. The tables show how different heating systems convert the same heat requirement into different amounts of energy bought, depending on operating temperature and system efficiency.

Energy costs use Ofgem price-cap unit rates for London (Direct Debit, 1 Jan–31 Mar 2026):

  • Electricity: 27.00 p/kWh
  • Gas: 6.03 p/kWh

Any difference in annual running cost reflects system efficiency only, not changes in insulation, comfort, or how warm the home is kept.
(Source: Ofgem – Average gas and electricity usage; Ofgem – Price cap unit rates by region)

How heating temperature affects your annual energy bill

The table below, shows the effect that different flow temperatures have on a heat source’s efficiency and your energy bills. All figures shown assume exactly the same amount of heat delivered to the home. The savings come from improved system efficiency, and are not from lowering comfort levels or more efficient zoned heating management.

Heating system Rapid Response®
30°C Flow Temperature		 Rapid Response® 45°C Flow Temperature Low Temperature Radiators 55°C Flow Temperature Radiators 65°C Flow Temperature
Ground Source Heat Pump
(Stiebel Eltron WPE-I 12 H		 £556 / year £652 / year £741 / year £854 / year
Air Source Heat Pump
(Octopus Cosy 6)		 £689 / year £865 / year £986 / year £1121 / year
Gas Boiler
(Typical mains gas)		 £697 / year £708 / year £719 / year £738 / year
typical home

What this means for your home

The table above shows one simple but important truth:

Lower heating water temperatures mean lower running costs – especially with heat pumps.

Rapid Response overfloor heating allows your heating system to run at much lower flow temperatures than radiators and is far more controllable than traditional screed systems, leading to more potential efficiencies. Typical overfloor systems operate between 30–45 °C, whereas radiators usually require 55–65 °C or more to deliver the same level of warmth.

That difference in temperature is what drives the cost savings shown above.

comfortable lady enjoying warmth and home

Will my home still be warm?

Absolutely, comfort is increased not reduced.

Overfloor heating works by gently warming the entire floor area, which then radiates heat evenly into the room. This produces a more consistent and comfortable environment, with fewer cold spots and less temperature swing than radiator systems.

All figures shown assume exactly the same amount of heat delivered to the home. The savings come from improved system efficiency, not from lowering comfort levels.

air source heat pump

Why Overfloor heating makes such a difference with heat pumps

Heat pumps are most efficient when they operate at low water temperatures.

  • Gas boilers gain only small efficiency improvements at lower temperatures
  • Heat pumps gain large efficiency improvements
  • Ground source heat pumps benefit the most, followed by air source heat pumps

This is why overfloor heating is often the deciding factor in whether a heat pump is cheaper to run than gas.

The same heat pump paired with radiators may cost significantly more to operate than when paired with overfloor heating.

Read more in our article underfloor heating vs radiators for heat pumps,

new build home with underfloor heating

What this means when choosing a heating system

If you are:

  • Building a new home
  • Renovating floors
  • Replacing your heating system
  • Considering a heat pump now or in the future

Then Wunda Rapid Response®,overfloor heating is one of the most effective ways to reduce long-term running costs.

It:

  • Works efficiently with gas boilers today
  • Unlocks the full efficiency of heat pumps
  • Future-proofs your home for low-carbon heating
  • Aligns with current UK Building Regulations
installing rapid response underfloor heating

Why Rapid Response® overfloor heating

Rapid Response® overfloor heating systems are designed to operate efficiently at very low flow temperatures while delivering fast response times and precise control.

This allows homeowners to achieve the low running costs shown in the tables, without sacrificing comfort or usability.

This article covers why Rapid Response Wundafloor is the better choice for most rather than traditional Screed Underfloor heating systems, which are slow to respond.

 

In summary

The question is not whether low temperature systems such as Rapid Response® Wundafloor can heat your home, the real question is how efficiently that heat is delivered.

Lower temperatures mean higher efficiency, and higher efficiency means lower bills.

Detailed Costings for Each Technology

Ground Source Heat Pumps

Output / Flow Temp (°C) Efficiency
(SCOP)		 Cost of Heat (p/kWhₕ) Annual Cost
(£/yr)
25 5.87 4.60 £529
30 5.59 4.83 £556
35 5.30 5.09 £586
40 5.03 5.37 £617
45 4.76 5.67 £652
50 4.48 6.03 £693
55 4.19 6.44 £741
60 3.91 6.90 £794
65 3.64 7.43 £854

Annual Running Cost of a Typical Ground Source Heat Pump

The table above uses the SCOP versus output temperature data for a Stiebel Eltron WPE-I 12 H 230 Premium, taken from the MCS product directory, with 25 °C, 30 °C, 60 °C and 65 °C values extrapolated beyond the published 35–55 °C range across the emitter temperature range (including overfloor heating).

Air Source Heat Pumps

Output / Flow Temp (°C) Efficiency
(SCOP)		 Cost of Heat (p/kWhₕ) Annual Cost
(£/yr)
25 4.93* 5.62 £646
30 4.62* 5.99 £689
35 4.31 6.42 £738
40 4.00 6.92 £796
45 3.68 7.52 £865
50 3.45 8.03 £923
55 3.23 8.57 £986
60 3.03 9.14 £1,051
65 2.84 9.75 £1,121

Annual Running Cost of a Typical Air Source Heat Pump

The table above uses the SCOP versus output temperature figures for an Octopus Cosy 6 taken from the MCS product directory, with 25°C and 30°C values extrapolated across the emitter temperature range (including overfloor heating).

Gas Boilers (Mains Gas)

Output / Flow Temp (°C) Return Temp
(°C)		 Efficiency
(approx, gross)		 Cost of Heat (p/kWhₕ) Annual Cost
(£/yr)
25 5 99.50% 6.06 £697
30 10 99.50% 6.06 £697
35 15 99.00% 6.09 £700
40 20 98.50% 6.12 £704
45 25 98.00% 6.15 £708
50 30 97.30% 6.20 £713
55 35 96.50% 6.25 £719
60 40 95.30% 6.33 £728
65 45 94.00% 6.41 £738

Annual Running Cost of a Typical Gas Boiler

The table above uses published boiler efficiency versus return temperature behaviour (condensing below ~55°C return). A fixed ΔT of 20°C is assumed, so return temperature is flow minus 20°C, and efficiency is interpolated from published BRE/SAP and manufacturer test regimes (e.g. 80/60 and 50/30).

wunda rapid response underfloor heating plans

Thinking about a new heating system?

Whether you are installing a heat pump now or keeping a gas boiler today, Wunda Rapid Response® overfloor heating allows your system to run at lower temperatures, lower cost, and higher efficiency – now and in the future.

Speak to us about designing a system for your home.

Your Questions

Wunda’s Rapid Response® overfloor boards are made with high-strength EPS 400 and aluminium that offer exceptional durability. Their 400 kPa compressive strength is comparable to supporting a Mark V Light tank!

Find out more in this blog post

A popular misconception is that thermal mass, or screed holding heat, is a benefit. In reality, it takes hours to warm up and cool down, resulting in a system that needs constant trickle feeding to maintain an ambient temperature, even when not in use. It is a store of energy that you need to put in, to get out. This leaves users with an uncontrollable system, which is far from ideal when trying to warm up. It is even worse when trying to cool down a space, often requiring opening windows to adjust the temperature. This is not the most efficient use of energy. It is better to use energy when you need it, where you need it.
The Wunda rapid response system solves this problem by putting the energy straight into your room. Using low water temperatures (as low as 30 degrees). Users can warm rooms as needed rather than maintaining a constant trickle feed when rooms are not in use. While quick heat-up and cool-down chemical screed systems are available, they are a hassle to retrofit. In contrast, the Wunda rapid response system is easy to install, offers the same energy-saving benefits, uses low-temperature water, and provides better control.

It’s a common misconception that underfloor heating is a luxury accessory to keep feet warm. In fact, it’s the most efficient heating system available! By replacing your radiators with Wunda water-based underfloor heating, you can save space, increase comfort, and make your home net zero ready. 

To learn more about our water-based underfloor heating systems, please visit our website at Wunda Group. 

The insulative properties of our Rapid Response® boards have been tested at the University of Salford’s UKAS accredited testing lab. The results are as follows: 

  • 20mm of Rapid Response® has an R-value of 0.447 (+/- 2%). 
  • 16mm of Rapid Response® has an R-value of 0.379 (+/- 2.8%). 

Please note that while the EPS material is insulative, it is not a replacement for insulation. In a new build, the property is expected to be built in line with up-to-date building regulations. 

If you have an older property that is successfully heated by radiators, the Rapid Response system will heat more efficiently and effectively than radiators. However, if your home is unsuccessfully heated by radiators due to high heat loss, the heat loss should be addressed regardless of your choice of heating system. 

 

 How much height does this add to the room? 

Our Rapid Response panels come in two sizes: 16mm and 20mm (about the size of a 20 pence piece). To calculate the total build-up height, add this to the height of any necessary decoupling layer such as a 10mm screed (tiling, LVT) along with your floor finish. 

Please note that the choice between the 16mm and 20mm panel has little to no effect on heat output but will affect price. Systems using the 16mm panel are more expensive than those using the 20mm panel, due to an increased amount of pipe being necessary. 

 

The Rapid Response® system should be laid on as flat a surface as possible. The polystyrene boards are fairly forgiving, but if there are any dips, holes, or undulations in the floor, we recommend using a levelling screed to deal with them. The floor should be dry and free of dust, oil, or other contaminants to ensure that the adhesive sticks properly. 

For more information about floor preparation, check out this blog post: How To Install Underfloor Heating On Concrete Floor – Wunda Group. 

Our Rapid Response® system is compatible with most floor finishes, including carpet and underlay (up to 2.5 tog), wood, LVT, laminate, concrete, and tiles. Wunda Rapid Response® high-density boards also support heavier floor finishes such as marble and stone tiles. These boards are approved by leading tile adhesive manufacturers to be laid directly on top without the need for an intermediary layer. This helps to reduce system cost, build-up height, and decrease installation time. 

For those opting for a wood or vinyl finish, we supply floor probes to protect the floor finish. Please note that wood products such as Maple and Beech are not compatible. 

For more information on each floor finish, please visit our website at Underfloor Heating for Different Floor Types | Wunda Group. 

To ensure that our rapid response system works optimally, we recommend installing it on a fixed floor made of wood, concrete, tile, or stone. This will prevent any movement and ensure that the system functions smoothly. Please note that the system should not be installed on top of any floating floor, and any such floor finish should be removed first. This applies to carpet, LVT, and laminate flooring. If you wish to install the system on top of tiles, please ensure that the floor is dry and free of any contaminants. 

Some customers prefer to remove any fixed floor finishes to keep the build-up height as low as possible. We recommend that any existing old asbestos flooring tiles be professionally removed before laying a new floor on top. This will ensure the safety of everyone involved. 

Water based underfloor heating does require some maintenance. In comparison to radiators water underfloor heating needs very little maintenance and the maintenance it does need is easier to carry out, as the system is maintained from one central point – the manifold.

The maintenance follows a similar to process to central heating with radiators. Ensure there’s no air in the system by releasing at the manifold and turn on after summer before the depths of winter to check all is running smoothly.

A Rapid Response® floor heating system produces heat in as little as 30 minutes because it has a level of controllability not seen before in under floor heating. Combined with our Home Heating Controls it can be turned on, off, up, down in individual areas of the home at the touch of a button on your smart phone, Ipad or laptop from wherever

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