Heat pumps three times more efficient than gas boilers, research finds

Air Source Heat Pumps (ASHPs) can operate with high efficiencies, even in cold weather conditions, according to interim heat pump performance data released as part of the Electrification of Heat (EoH) Demonstration Project.

Funded by the Department for Energy Security and Net Zero (DESNZ), the EoH Demonstration Project is working to understand the technical and practical feasibility, and constraints of a mass rollout of heat pumps into British homes, a statement has said.

A total of 742 heat pumps were installed by the delivery contractors – Warmworks, E.ON, and OVO Energy – into a broad spectrum of housing types and ages. These heat pumps are being monitored throughout the trial to assess their performance.

The interim data and results of this monitoring have been released by Energy Systems Catapult. The analysis within both the Interim Insights from Heat Pump Performance Data and Interim Heat Pump Performance Data Analysis Report, is to be refreshed and additional analysis undertaken after the completion of the projects monitoring period in Autumn 2023.

Seasonal Performance Factors (SPFs) indicate the in-situ efficiency of a heat pump system over the course of 12 months. The median SPF observed in ASHP systems during the EoH Demonstration Project was 2.80 (280%). This is an increase of around 0.3 to 0.4 (30-40%) since the Renewable Heat Premium Payment scheme (RHPP) heat pump trial was undertaken between 2011-2014. However, whilst the average performance has improved, performance variation remains high.

The EoH Demonstration Project analysed the performance of heat pumps on some of the country’s coldest days and found only a marginal decline in whole system performance, a statement has said. The median ASHP system efficiency was 2.44 (or 244%) on the coldest days of the year. This result indicates that heat pumps continue to operate with high efficiency in a wide range of property types even in cold weather conditions, a statement has said.

High temperature ASHPs are a viable solution for meeting the heating demand of a property. Use of high temperature units reduces the need for deeper retrofit and provides a potential solution for less efficient homes.

The data released by Energy Systems Catapult demonstrates that the high temperature ASHPs used in the project have performed with similar efficiencies to low temperature ASHPs. Heat pumps are controlled to only demand higher temperatures when it’s colder outside.

The hybrid heat pump systems were commissioned to run ‘cost-optimally’, with the system choosing when to operate the boiler or heat pump based on which is the cheapest option at a given time. Generally, the heat pump would meet the base space heating requirements and the boiler would cover hot water production and meet peak space heating demand.

The performance data reveals that the heat pumps in hybrid systems typically met about 39% of the space heating demand. They also had a median heat pump efficiency of 2.37 (237%), which is lower than standalone ASHPs; giving an estimated overall heating system efficiency of between 1.26-1.42 (126-142%), depending on the efficiency of the boiler and the proportion of hot water demand.

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