Heat pumps and the UK’s heat decarbonisation: Lessons from an Ofgem dataset of more than 2,000 domestic installations

The decarbonisation of heat in the UK represents an urgent and colossal challenge. Heat pumps are cited as a crucial tool to lower CO2e emissions, and the UK Government plans to boost installation rates from 30,000 per year to 600,000 by 2028. UK heat pump field trials completed in 2010 and 2015, however, reported disappointing results with many installations failing to deliver benchmark efficiencies. There is no evidence from more recent UK studies to show that performance has improved significantly.

To investigate actual heat pump performance, a dataset was obtained from the Office of Gas and Electricity Markets (Ofgem) for a sub-set of installations that are subject to strict monitoring under the Renewable Heat Incentive (RHI). A spreadsheet methodology was developed to interrogate the dataset and calculate the in-situ heat pump efficiencies and those actual results were compared to the installer forecast efficiencies that were included in the dataset.

The analysis found that more than one quarter of the main sample and 28% of Air Source Heat Pumps (ASHPs) were performing with an efficiency below the Seasonal Performance Factor (SPF) benchmark of 2.5. No correlation between the installer performance forecasts and the actual SPF results was found in the main samples examined. Additionally, the analysis found no improvement in performance after the UK installation standard was overhauled in 2017.

Overall, these results raise significant questions about installation design and execution and about the methodology used for consumer performance forecasts. It is concluded that information asymmetries may damage consumer confidence in heat pumps and that this may limit market growth.