Heat pumps can be an efficient alternative to electric, oil or LPG heating says EST field trial
Posted by Cathy Debenham on 15 August 2013 at 9:12 am
Heat pumps can provide an efficient alternative heat source for householders currently heating using electricity, oil, LPG or solid fuel according to phase two of the Energy Saving Trust's (EST) heat pump field trial.
Well installed heat pumps, in homes which have adequate insulation, can reduce running costs substantially over the system's lifetime according to the study. An air source heat pump (ASHP) could save between £150 (replacing oil) and £530 (replacing electric economy 7 storage heating) a year. It would also reduce carbon emissions by 1,400 - 5,700kgCO2 a year. A ground source heat pump (GSHP) could save between £300 (oil) and £685 (electric) a year.
These figures are based on an average performing heat pump* installed in a well-insulated, detached 4-bedroom house. In addition, heat pumps are eligible for the domestic RHI (renewable heat incentive) which will be paid at 7.3p per kWh of renewable heat generated for ASHP, and 18.8p per kWh for GSHP. This aims to put the cost of installing a renewable heat technology on a level playing field with more traditional heating systems.
Main findings of the heat pump field trail
1. Heat pumps can be an efficient alternative.
2. They are sensitive to design and commissioning. However, between the phase one trial in 2010 and this trial the EST says that the reasons for previous underperformance are understood, and have been addressed by the new, improved MCS standards.
3. While most people taking part in the trial were happy with the heating and hot water provided by their system, they wanted more information. Installers and manufacturers should work to develop customer understanding of their system.
4. Different aspects of a heat pump system have different impact on its performance. In particular, auxilliary and immersion heaters can have a significant impact on the efficiency of the system, and customers will benefit from knowing that.
5. It's often said that the most efficient way to run a heat pump system is to have it running continuously. However, the trial found that a number of well-performing systems were controlled non-continuously, and their owners were satisfied with their performance.
6. Users' understanding of their systems is varied. The data suggests that if people understand about system design and control, the overall performance is likely to be better.
Understanding of heat pumps has improved
Phase one of the heat pump trials, which was published in 2010, had mixed findings with wide variations in performance. Problems were identified with installation, sizing of systems and lack of understanding of how to use the system among some of those taking part.
Forty four sites that performed poorly in the first trial were included in the second trial. All of them were analysed to identify what factors were impacting on their performance. Of those 32 had modifications, and users were given guidance about how to use the controls and manage the system to optimise performance. Performance improved in 20 of those systems.
Of the heat pumps in the trial (after interventions to improve performance) 20 out of the 21 ground source heat pumps could be defined as renewable** under the EU directive, but only nine out of the 15 air source systems from phase one met the standard. Six newly installed systems were also included in the field trial and one of them failed to meet the standard.
These latter heat pumps were installed to higher standards than the original ones tested, but not to current MCS standards. Even so, this finding highlights the importance of ensuring that you find a installer who has experience of sizing, installing and commissioning heat pumps if you want to get a good system.
*An average performing heat pump in this study had SPF(H4) of 2.45 for ASHP and 2.82 for GSHP. SPF(H4) is calculated by dividing the heat supplied by the heat pump for space heating and to the domestic hot water tank + heat produced by the immersion by the electricity used by inlet fans/pumps + auxilliary + heat pump + immersion +building fans or pumps.
**To be classified as renewable under the EU Renewable Energy Sources Directive (and receive the renewable heat incentive) a heat pump must have a minimum SPF (H2) of 2.5. This is calculated by dividing the heat delivered for space heating and to domestic hot water tank by the electricity to inlet fans/pumps + heat pump.
More information about heat pumps from YouGenCathy Debenham
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