Ground source heat pumps explained Ground source heat pumps - trial results

Heat pump action

The design and installation of a ground source heat pump affects how efficient it is

In order to investigate how well air source heat pumps and ground source heat pumps perform, the Energy Saving Trust (EST), one of the leading organisation on helping people save energy, has run a trial on 83 different heat pumps installed in the UK.

In phase one, the EST monitored 54 ground source heat pumps and 29 air source heat pumps in UK properties over a 12-month period from 2008 to 2009, to identify which factors affect how well a heat pump works and to better understand how households are actually using heat pump technology. See our guides on ground source heat pumps and air source heat pumps to understand more about how they work.

Heat pump trial – key findings

The trials found that correctly installed and operated heat pumps can perform to a very high standard in UK homes. During the trial, the EST measured the Seasonal Performance Factor (SPF). This is defined as the amount of heat the heat pump produces compared with the amount of electricity needed to run the system. The average SPF for an air source heat pump was found to be 2.45. For ground source heat pumps it was found to be 2.82.

Many systems appeared to be installed incorrectly, and control systems were generally complicated. Phase one of the trial came to the following conclusions:

  • Design and installation. There was a big variation in performance, with several early heat pumps incorrectly designed or installed.
  • Simplicity. The best heat pumps tended to be the simplest in design and scope.
  • Hot water. It's unclear whether using a ground source heat pump to also produce hot water impacts overall efficiency.
  • Heating controls. The EST described an overall 'failure to explain proper control requirements' to heat pump customers, with many unsure how to properly use the controls to work their system.
  • After-care – The installation company should be required to provide quality after-sales services.

What to expect from a heat pump-powered system

  • Your home may take longer to heat up.
  • If you're using radiators, expect them to feel warm rather than hot – heat pumps produce lower temperatures than a boiler.
  • You'll probably need to have your heat pump on for more hours a day than you would with a boiler.
  • You might need a separate electric heater to help provide all your heating and hot water needs.
  • The heating controls that come with a heat pump can be complicated – insist on easy-to-use controls and a demo from the installer.
  • Check the credentials of the ground source heat pump installer you're using – they should be accredited by the Microgeneration Certification Scheme, be able to design a system specifically suited to your property and offer an after-care service.

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