At time of writing we are in election mode with various Party manifestos being released. Net Zero is high on the agenda and, with some variations in transition speed, there remains cross Party agreement to achieve the 2050 commitments. When it comes, however, to addressing our politician’s Net Zero promises those of us in the Building Services industry face some challenging conversations.
In these ‘cost-of -living crisis’ days it’s a tough sell to explain that the chosen technology of air source heat pumps (ASHP) has a price tag of four to five times that of a good modern gas boiler. The conversation doesn’t get any easier when additional costs for building fabric improvements or replacement radiators come in to the mix.
Notwithstanding this the subject moves to a different level when one considers that, in Great Britain, electricity is about four times more expensive than gas, according to the regulator’s latest energy price cap. It’s good news, therefore, that ASHPs operate at much higher efficiencies than gas boilers. But is this extra efficiency enough to make them cheaper to run? As their price tag is so much higher, this has got to be a reasonable question to ask.
Surely, if the Capital outlay is so much higher than a boiler, this has got to be a good question to ask. Are they cheaper to run than gas boilers? How can we know?
Well, as a starter, it’s important to look at independent studies from those without vested interests. A case in point is the respected Energy correspondent, Jillian Ambrose, who has previously written for the Telegraph and now writes for the Guardian. Ms Ambrose’s articles are well researched and balanced so are worth a close look. In one of her recent articles, published in The Guardian (May 13th 2024), entitled ‘Are heat pumps more expensive to run than gas boilers?’ a study, carried out by the Regulatory Assistance Project (RAP), highlights some highly relevant findings. The RAP is an independent, global non-governmental organisation which has no commercial axe to grind so it should be safe taking what it says at face value.
The author of this RAP paper (issued to the Carbon Brief), Dr Jan Rosenow, essentially ascertains that ASHPs have similar running costs to gas boilers. In the language of the ASHP sector, he references the Seasonal Co-efficient of Performance (SCOP) as the measure of how this can be assessed.
“An ASHP with a SCOP of more than 3 will match the running costs of a gas boiler.”
Reference – Dr Jan Rosenow, RAP
Rosenow’s analysis shows that an ASHP with a SCOP of more than 3 (for clarity that is essentially a 300% mean annual efficiency) will basically have the same running costs as an 85% efficient gas boiler. This SCOP value rises to 3.2 if compared to a 90% efficient modern gas boiler.
So how does this compare to ASHP performance in the UK? According to the Energy Systems Catapult a recent study found that installed domestic ASHPs typically have a SCOP of 2.9 – making them, at least based on this 750 unit sample, a little more expensive to run than a gas boiler.
When it comes to selecting a commercial air source heat pump it is, therefore, a good idea to look for a published SCOP of at least 3 if replacing an existing gas boiler. In this way the installation of an ASHP will not only save carbon but it could just also save a little cash as well. Notwithstanding this claim it’s clearly important that necessary fabric improvements are made as well as sound design and good installation practices are followed.
Strebel Ltd, established in 1975, offers a wide range of commercial ASHP machines with outputs of 25kW up to 100kW. All of these machines boast SCOP results of between 3.4 and 3.6 at water temperature of 550C, in line with the latest Part L Building Regulations, which is significantly over the RAP paper’s target of between 3 to 3.2.
Therefore, in answer to the posed question it can be confidently claimed that ‘Yes. Running an ASHP can save cash as well as carbon’. That is – as long as it’s a Strebel ASHP.
