Heat pump average cop for the year 2.7

MickDavid

We have had installed a air to water heat pump, in the last year its average efficiency is 2.7, no where near the 4.5 etc that are publicised. They are worse than the diesel car fraud

michaels

I believe in the past an official testing body got similar results but there are always claims that the newest latest greatest tech will be more efficient.  Problem is that you need most heat output when the weather is coldest and they are at their least efficient....

As electricity prices are generally just over 3x as much as gas but gas is not 100% efficient you probably need a cop of more than 3 for the energy cost to be cheaper with an ashp.

Cardew

Welcome to the forum.

A overall system COP of 4.5 is unrealistic - much like some advertised MPG figures for cars or expected range for electric cars.

A COP of 2.7 is in line with the results of the trials carried out for the Energy Saving Trust. Many of the enthusiastic ASHP owners on this forum expect an overall COP of a little over 3.0.

Reed_Richards

If you installed with an MCS registered installer you should have been given a figure for what Seasonal Coefficient of Performance you would achieve.  The figures I was given were 3.2 for heating and 2.9 for hot water.  I have no way of measuring exactly what I get but the average figure is somewhere in the vicinity of 3.

The only was you could possibly get a SCOP of 4.5 would be to use a water flow temperature of around 35 C and not very much hot water.  So you would need a house with Underfloor Heating throughout, properly adjusted.  If that's not you then you were misled but I think it must have been your installer who misled you.  So that's more like VW giving honest figures about their diesel car fuel consumption but then the person in the car showroom telling porkies.  

Martyn1981

MickDavid said:

We have had installed a air to water heat pump, in the last year its average efficiency is 2.7, no where near the 4.5 etc that are publicised. They are worse than the diesel car fraud

Hi, isn't that about right? The figure I typically see is ~2.9.

shinytop

MickDavid said:

We have had installed a air to water heat pump, in the last year its average efficiency is 2.7, no where near the 4.5 etc that are publicised. They are worse than the diesel car fraud

I don't think anyone sensible publicises 4.5.  That's the nominal test figure, done in test conditions, which will never be achieved in real life.

2.7 is OK but a well designed system, even with radiators, should do a bit better. 

If you post some details of your system, I and a few others can maybe suggest ways to make it more efficient.

Remember COP isn't everything though; I'm much more interested in energy/£ used. I've just made some changes to my system that make my house warmer, lower my COP but make little/no difference to the energy used.  

matelodave

I'm sure that a heatpump, under the control of the lab technician standing in a lab surrounding by test gear and properly monitored will achieve a much better COP than one standing outside no 17 Acacia Avenue in all weathers and temperatures and heating the house and hot water under the control of all the occupants who have a varying ideas of comfort.

I'd guess that most people unless they put some effort into understand and tuning their systems wont get much better than 2.5 to three depending on how they use their systems. In much the same way as the fuel consumption of my car varies whether I blatt up the motorway at 80, cruise at 50 or even tow my 1.6 tonne caravan.

If you want to get a more accurate assessment of your system performance then you need to do a bit of measuring of power consumption, tempertaures, water flow etc. Have a look here - https://docs.openenergymonitor.org/applications/heatpump.html#my-heatpump-dashboard

Meatballs

Have you spent some time adjusting the weather compensation flow temperatures?