Using Heat Pumps With Underfloor Heating

In Summary: Heat Pumps & Underfloor Heating

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Air source heat pumps do work with underfloor heating (UFH), both existing and new systems. 

Coupling heat pumps with underfloor heating is one of the best ways to maximise their efficiency; your pump can run at a much lower flow temperature. Dropping the flow temperature on an air source heat pump from 50°C to just 35°C could increase its efficiency by 16%!

These systems are much more efficient than a gas boiler and radiator setup. By using underfloor heating, your system can heat a much bigger area slowly, not overworking your heat pump. 

Expect a typical system to cost around £20,000. That covers costs to install both a heat pump and underfloor heating. However, there’s a good chance you’ll receive a £7,500 government grant (Boiler Upgrade Scheme), dropping costs down to £12,500.

And remember, design is the key to efficiency. Designing a system in detail will lead to not overspending by buying a larger pump than you need, as well as increased efficiency; lower energy bills!

You can get installation prices for heat pumps that work with underfloor heating here.

Do Heat Pumps Work With UFH?

Heat pumps work incredibly well with underfloor heating. In fact, using UFH rather than the radiators you’ve been using with your gas boiler is the most efficient setup for a heat pump. 

If you read our guide covering air source heat pumps & radiators, you’ll see we generally suggest radiator output should be 2.5x compared to radiators used with a gas boiler. This allows your air source heat pump to run at a much lower flow temperature; the key to it working efficiently and lowering your energy bills.

Why Does UFH Heating Work So Efficiently With A Heat Pump?

Flow temperatures for air source heat pumps tend to sit in the 35°C-55°C range. Compare this to the approximate 70°C flow temperature of a gas boiler. The lower the flow temperature they can run at, the more efficient they’re going to be. 

We can see just how important flow temperature is when we look at the Vaillant aroTHERM Plus 7kW heat pump (review here), when run at different flow temperatures: 

• Flow temperature of 35°C: 4.36 (436% efficient)
• Flow temperature of 40°C: 4.13 (413% efficient)
• Flow temperature of 45°C: 3.91 (391% efficient)
• Flow temperature of 50°C: 3.65 (365% efficient)

By dropping flow temperature from 50°C down to 35°C, you’ll see an increase in efficiency of over 16%! 

For every 1kWh of electricity consumed at 35°C, the Vaillant 7kW heat pump will generate 4.36kWh of heat. A gas boiler is approximately 94% efficient, it would only produce 0.94kWh of heat for every 1kWh of energy it consumes.

This is why when converting from a gas boiler, you want radiators with bigger surface areas and higher overall output potential; so you can reduce flow temperature. 

Underfloor heating covers a much bigger surface area than a set of radiators, and that’s going to mean your air source heat pump works at maximum efficiency.

Installation Costs For A Heat Pump & UFH System

Expect installation costs for an underfloor heating system combined with a heat pump to cost in the region of £20,000. However, the overall cost here would be reduced to approximately £12,500 after accounting for government grants (such as the Boiler Upgrade Scheme).

This isn’t a cheap property upgrade, but it could add thousands onto the value of your property, and save you hundreds each year in energy bills. For those looking for heat pump grants, the Boiler Upgrade Scheme is the most common funding that these installations are eligible for. 

You should expect installation costs to be split approximately 50/50 between your heat pump / underfloor heating system. 

As an example, using our heat pump configuration tool here, you’d get a price of just over £3,000 for your heat pump installation, after discounting the £7,500 government grant: 

Designing Systems For Maximum Efficiency

Designing and installing the right setup is incredibly important. A properly designed underfloor heating system that utilises a heat pump is going to knock huge percentages off your utility bills. 

The two most important things to consider are selecting the right sized heat pump, and planning your UFH installation.

Heat Pump Sizing

The first thing to consider is the type of heat pump and size you want to install. Air source heat pumps work incredibly well in efficient homes, but only if you buy one that’s the right size. 

Buy one that’s too small? It will have to work overtime to keep up with demand. 

Buy one that’s too big? Not only will installation costs be much higher than they need to be, but the motor cycling on and off constantly is going to mean it wears out sooner than it should. 

As a guideline, a typical 3-bed semi-detached would need a heat pump in the 5-7kW range. 

However, this isn’t a one size fits all approach. So, check out our guide to heat pump sizing here, or, jump over to our heat pump configuration tool here. 

UFH Installation

The design of your underfloor heating system is going to have a direct impact on how efficient your air source heat pump can be. An MCS registered UFH installer will be able to spec and design a system to maximise efficiency and will: 

• Space pipes closely together, for minimal heat loss
• Use large diameter UFH pipe to cover as large a surface area as possible

The better the UFH is designed, the less energy you’ll need to use via your air source heat pump. And one of the best ways to do that is to ensure that the return temperature is as close to the flow temperature as possible by piping the system correctly.

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