Heat pumps, made simple

"Compared to a gas boiler, you could reduce your emissions from heating your home by around two thirds."
Here’s how it works:

According to Ofgem (sourced August 2024) the typical annual gas use for a medium sized home in the UK is 11,500 kWh. According to the Government Emission factors (July 2024) the carbon dioxide intensity of a kg of natural gas per kWh is 0.1829 kg/kWh. Resulting in CO2 emissions of 2,103kg per year (11,500 * 0.1829 = 2,103.35) from that amount of gas usage.

We've made a simplifying assumption that all of this gas goes into heating the home (so assuming there are no other gas appliances like a hob or fire). A government study estimated the mean efficiency of combination boilers at 82.5%. This means that 9,488 kWh of the gas purchased was actually used to heat the home and hot water. The rest was wasted in the combustion process (so still releasing emissions).

So now we know the house needs 9,488 kWh of heat a year, how do we figure out how much electric is used to power a heat pump producing the same amount of output? From another government funded study, it was found that the Seasonal Performance Factor for the heat pumps in their study was 2.91 (which is relatively low). This effectively means for every 1 kWh of electricity used, the heat pump generated 2.91 kWh of heat (291% efficiency, vs 82.5% efficiency of the gas boilers in the other study).

So 9,488 / 2.91 = 3,260 kWh of electric is used to power the heat pump. Using the same Emission Factors data the carbon dioxide intensity of electricity generation and transmission in the UK is 0.2254 kg/kWh. Therefore, the approximate emissions generated from the electricity used to power the heat pump are 735kg (3,260 * 0.2254).

Finally, the carbon saving is 1,368kg a year (2,103kg - 735kg) or a saving of 65% (1368kg / 2,103kg). 

Why have we included a £7,500 government grant in our prices?

Whilst there are eligibility criteria to access the £7,500 of grants available in England, Wales and Scotland most homeowners are likely to be able to obtain the funding. To check specific eligibility criteria we have put together this eligibility checker tool, which we will also use as part of your free home assessment. We have also written this guide to government grants.

We always aim to provide the best possible service to our customers, but sometimes things can go wrong. We'll regularly ask you how we're doing, because it gives us the opportunity to put things right and improve our services. You can always contact us if you have any concerns. You can read more about our approach to resolving complaints here.