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COP (Coefficient of Performance) and SPF (Seasonal Performance Factor)

COP or Coefficient of Performance is often referred to when discussing a heat pump’s performance.  COP is the means of stating the ratio of units of heat output for each unit of electricity used to drive the compressor and pumps (or put even more simply, it’s the ratio between provided and consumed energy).

COP is an instant measurement of efficient and varies with both the temperature of the source and the heating water temperature. Expected COP is taken as an annual average return - obviously in winter it may be lower and higher in the summer.  Thus, over a year, the heat pump operates in various conditions with varying efficiency.  COP is easy to measure but doesn’t give a fully realistic reflection of a performing system under real conditions (for this, see SPF).  It is good for indicating a heat pump’s performance at a given moment in time.

All the points we've outlined below are equally important to ensure your heat pump performance, that its efficiency is maximised and that running costs are reduced in the long term.

 

  • Method of construction; concrete and screeds are the ideal partner when combined with underfloor heating and heat pumps.
  • Up to standard insulation and U-values. 
  • Correctly fitted insulation; careless installed insulation will allow heat to escape and renders the insulation job worthless. 
  • Amount of ground to install trenches. Please contact us to establish whether you have enough ground and the soil type suitable for installation of a trench system.  IHS does not recommend using the slinky method in a trench system! 
  • Method of heat delivery (underfloor heating or radiators?) and how well the system is installed and integrated 
  • System programming and sizing


If the above elements are in place, a heat pump from IHS should deliver the following efficiencies

 

  • Efficiency/COP with trenches - 1:4.4 *
  • Efficiency/COP with closed loop (borehole) - 1:4.4
  • Efficiency/COP with open well - 1:5.5
  • Efficiency/COP Air Source Heat Pump - 1:4.2


* In a Carbon Trust testing programme, the IDM Terra HGL 15 ground source heat pump was submitted to BSRIA (a major UK test and research provider to construction services in the UK).  The heat pump delivered a measured COP of 1:4.76.  At HIS we were thrilled with this outstanding result which was further endorsed by BSRIA’s purchase of a 15kW heat pump for their own factory shortly afterwards!


SPF – Seasonal Performance Factor

Another characteristic figure is extremely important and shouldn’t be confused with COP.  This is called the Seasonal Performance Factor (SPF).  It’s a key element in our system design calculations, taking the entire heat pump’s consumption (compressor, circulation pumps and electric immerser) into account while simultaneously taking account of influencing factors such as ground temperatures.

The SPF describes the ratio of the amount of heating power supplied by the heat pump over a whole year and the amount of electrical energy consumed to provide this power.  The SPF reflects the rate of use of the installed heat pump.  In a well-designed and installed ground source heat pump, the expected SPF from an air to water heat pump should be between 2 and 4 and in a ground or water source heat pump, should be between 4 and 5.