"Combine the improving efficiencies of heat pumps with lower energy costs, and we’ll see the significant real-world savings consumers can make by switching to low-carbon heating."
- Tamsin Lishman, CEO of Kensa
‘In Situ Heat Pump Performance’ analyses Ofgem data on heat pump installations subject to metering for payment under the Renewable Heat Incentive (RHI). That metering provides data on both electricity consumption and heat generation from heat pump systems, enabling an analysis of the actual in-situ efficiencies of more than 1.7k installations of air source heat pumps (ASHPs) and ground source heat pumps (GSHPs).
The report analysed heat pump installations between 2017-22 in Great Britain, comparing findings against the RHPP field trials and the Electrification of Heat Demonstration Project. The average GSHP seasonal performance factor (SPF) has improved significantly from just over 3.0 in 2017 to 3.31 in 2022.
More than 16% of GSHPs and nearly 6% of ASHPs had in-situ efficiencies that were at or above their design Seasonal Coefficient of Performance (SCOP), and a third (33%) of GSHPs were performing at SPF 3.5 or above. However, there’s a high percentage of SCOPs that aren’t realistic and results for ASHPs are of particular concern.
67% of all GSHPs and nearly a third (30%) of ASHPs performed at SPF 3.0 or above, and after outliers were removed, no installation was found to be performing with an efficiency of less than 1.0. Although the vast majority of in-situ SPFs were found to be lower than the design SCOPs, nearly 6% of ASHPs and almost two in ten (16%) GSHPs had actual efficiencies that were above.
Unfortunately, these improvements are overshadowed by sizable gaps between average design SCOPs and in-situ SPFs, particularly wide for the most recent cohort of ASHPs. The report highlights that the correlation between design SCOPs and actual efficiency is weak.
Overall, these findings support conclusions set out in the Electrification of Heat Demonstration Project, calling for a review to be carried out (including further research into the current methods for calculating building heat loss, designing heating systems, and estimating efficiencies) to “evaluate how and why designs consistently produce unrealistic estimates for many consumers.”
Reacting to ‘In Situ Heat Pump Performance’, Tamsin Lishman, CEO of Kensa, said “This new research shows beyond doubt that heat pumps are the most efficient way of heating homes, three to four times more efficient than gas boilers. Importantly, the report shows ground source heat pumps perform well even when temperatures drop below zero, meaning reduced electricity demand and less pressure on the grid.
“This is a critical finding for how we achieve the mass roll-out of heat pumps, with millions of homes poised to switch to electrified heating. However, even with these efficiencies, today’s energy prices still mean it’s only slightly cheaper to run a heat pump over a gas boiler in a typical British home.
“At a time when we need to be weening ourselves off fossil fuels, it doesn’t make sense that electricity is still four times the price of gas. It’s vital the government acts now to remove the levies artificially pushing up the price of electricity,” she concluded.
