Heat pump warning: are they suitable for older homes?

We spoke to Stephen Bielby, operations manager at the Ground Source Heat Pump Association. He disagrees with Bosch’s claim that heat pumps are totally unsuited to older homes: “Any building will leak heat regardless of source, and all buildings and all heat technologies will benefit from a degree of energy efficiency or building fabric improvements. At this point in time, society must decide between leaking lower-cost, very-high-carbon heat (gas), or slightly more expensive, increasingly low-carbon heat (electrification with a heat pump).” 

Bielby also refers to a report published by Energy Systems Catapult, a body set up to accelerate the transformation of the UK’s energy system to net zero. “Apart from reporting steadily improving efficiencies (over previous trials), this programme could not identify a dwelling where there was no individual heat pump solution, be it air source, ground source or hybrid (a combination of a heat pump and a fossil fuel boiler).” In other words, there’s a suitable heat pump for every home.

The space required for gas boilers is quite different to that require by air source heat pumps and ground source heat pumps, as heat pumps come with some extra equipment.  But you won’t need a regular boiler, meaning you can regain this space. 

Air source heat pump 

With an air source heat pump, you’ll need to have a large box on the outside of your home and about two metres of clear space in front of the unit. The size of the unit will vary depending on the manufacturer and kilowatt output.  

Apart from the outside unit you’ll also need a hot water cylinder inside your home, and the size of the cylinder installed will depend on the usage requirements for the property.  

Exceptional asked heating, ventilation and air-conditioning manufacturer, Vaillant for some guidance on the ‘average’ size of the equipment: 

• External air source heat pump (monobloc and split system), based on Vaillant’s 7kW aroTHERM Plus: 110cm x 96.5cm x 45cm (43in x 38in x 13in)
• Internal unit (split system only), based on Vaillant’s 7kW aroTHERM Split: 44cm x 77cm x 35cm  (17in x 30in x 14in)
• Hot water cylinder, based on Vaillant’s 200 litre uniSTOR cylinder: 126.5cm x 59.5cm (50in x 23in)

Ground source heat pump

For a ground source heat pump, you’ll need land near your home that’s suitable for drilling boreholes or trenches. Inside your home, you need space to fit an indoor heat pump, which often contains the hot water cylinder. You can expect this to be about the size of a large-style fridge, according to the Energy Saving Trust.  

• Ground source heat pump, based on Vaillant’s FlexoTHERM: 118.3cm x 59.5cm x 60cm (47in x 23in x 24in) 
• Hot water cylinder, as above

Rajakoba’s acknowledges that some heat pumps do need more space inside or outside the home. But he explains that there are ways to mitigate this. “Where homes may be unsuitable for an external unit, these could be served with an internal ground source heat pump,” he says. “Or they could connect to a heat network that will almost certainly end up being driven by a centralised commercial heat pump, even if not from the outset.” 

Having the space for a hot water cylinder can also be a challenge, especially if your gas boiler is in a kitchen cupboard. Bielby says: “There are space-saving technologies, such as phase change storage devices, which have the potential to reduce the size of the cylinder by 75%.” 

Rajakoba’s comments come at a time when the Government is backing the installation of domestic heat pumps. The £60 million Heat Pump Ready Programme is providing funding for the Government’s target of 600,000 heat pump installations a year by 2028. This is being supported by a £450 million three-year Boiler Upgrade Scheme, offering households grants up to £5,000 for low-carbon heating systems.  

Bosch believes that hydrogen boilers are a more practical solution for older properties. However, the future for hydrogen boilers is still being determined, with major infrastructure barriers to overcome. For example, the national gas grid would need converting and pipes replaced in gas customers’ homes.  

There are other options for heating hot water, especially solar panels, although you can’t usually use them to heat your home, according to the Energy Saving Trust. You will also need to check if you can have solar panels installed. There may be restrictions if you live in a listed building, a conservation area or a national park. 

If you are thinking of installing a heat pump, it’s a good idea to ensure your home is properly insulated from the top down before you make the investment. Although key to any heating system, appropriate insulation is particularly pertinent with heat pumps, which work at lower internal temperatures. The Exceptional team will be sharing more news and features on heat pump development, so keep an eye on our updates.