The trial, run by the Energy Saving Trust and funded by numerous power companies, did reveal that ground source heat pumps, when installed correctly, did cut carbon and bills.

However, the results were ‘more varied than were expected’ and failed to show the technology

The results of the study, published earlier this week, found the 83 devices monitored for a year ‘underperformed’.

This, according to the trust, is caused by incorrect sizing of systems, complicated controls, a lack of education for householders using them and the use of multiple installers rather than a single contractor as used in Europe.

Head of Business Development for the Energy Saving Trust, Simon Green, said: “Over its lifetime, a high performing heat pump installed today will save CO2 even when replacing gas condensing boilers due to the planned decarbonisation of the grid.

“But there is no doubt that the results are more varied than were expected, with results showing both high and low performing heat pumps.

“We are securing funding to extend the trial, with the objective of defining the reasons for variation in performance levels so that we can inform industry about good practice and advise householders on exactly what to look out for.”

However, the Trust did say many of the five million people in the UK living off the gas grid could benefit from heat pumps.

Senior associate at Sustain, Kevin Boniface, said: “If insulation levels are poor, controls aren’t explained to users or conventional radiators are used, the heat pumps will struggle to provide the performance quoted by manufacturers.

“The problem is compounded by the fact that the figures published by many manufacturers don’t reflect real life situations, and so don’t take into account factors such as the need for back up heating systems particularly with air source heat pumps.

“As an independent consultancy, we are always looking for up to date research and good quality data that will help our clients.

“We welcome the results of the study but urge the Government not to delay the introduction of the Renewable Heat Incentive, which encourages a range of renewable technologies and is an important instrument for change.”

The trial began in early 2009 and monitored both technical performance and customers’ experiences for a full 12 month period.

Luke Walsh

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