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Air Source Heat Pumps – What COPs are needed for breakeven

It’s Christmas so I thought I’d spoil myself and do some additional fun analysis on Air Source Heat Pumps and different Coefficients of Performance.  (N.B. as with other analysis this is only valid for the house I am looking to buy.) For those that don’t know a Coefficient of Performance (COP) is the % heat energy that you get out of a heat pump compared to energy in.  An example is a COP of 200 means you get 200% energy out for energy in or twice as much energy out as energy in.  I know it sounds like some basic laws of physics are being broken but they aren’t.  The energy in is actually ‘work’ and the energy out is the conversion of low grade heat (in the outside air) to high grade heat (inside).  The COP therefore doesn’t take into account the amount of energy in the low grade heat as it is essentially free.

Coefficient of performance or heat pumps Analysis

The graph above shows the results of my efforts.  The yellow line is the basic savings that can be expected compared to the current heating system in the house.  You can see that a COP of 225 is required for there to be benefit.  The blue line is the savings including a rough figure for the Renewable Heat Incentive payments – in this case a COP of around 120 is required.  For these calculations I’ve using a one tariff electricity rate. Anyone want to share their thoughts?