Air source heat pumps

I should be clear my experience is limited to running the system in the French house, plus what I have gleaned online. The claims can be checked with a bit of analysis though.

Most of the video was marketing speak but I did spot a couple of claims.

The first was the rebate stuff which was UK specific and, to be honest, I have no idea how accurate that was.

Then there was (I think) 40% less CO2 emissions than gas - this page gives some comparison figures for CO2 emissions per kWh for various fuels.

Electricity (UK) - 0.527kg CO2 per kWh compared with 0.185 kg / kWh for natural gas and 0.245 kg per kWh for heating oil.

So, to be 40% better than natural gas you need to get down to 0.185 x 0.6 - 0.111kg per kWh. That needs a COP of 4.74 or better - uncannily almost exactly the figure they claimed in the video so that, on the face of it, stacks up.

But wait a moment gimoozaabi - the installation manual for their 8, 12 and 16kW units tells a slightly different story.

The performance data is on page 44, in the form of a table with vastly fewer data points than the Stiebel unit but what is there is sufficient

A8MA12MA16M
A7W356.3 / 4.4212.3 / 4.7212.3 / 4.72
A7W556.2 / 3.112.5 / 3.212.5 / 3.2
A7W656.3 / 2.712.4 / 2.612.4 / 2.6
A-2W356.7 / 2.9 12.0 / 3.315.5 / 3.2
A-2W557.1 / 2.112.0 / 2.515.6 / 2.4
A-7W357.0 / 2.912.0 / 3.013.2 / 3.0
A-7W557.1 / 2.112.0 / 2.215.3 / 2.2

A7W35 means intake air 7° with a water flow at 35° and the figures are heat output/COP.

The claim that heat output is maintained down to an air temp of -7°C seems to hold, more-or-less but the COP drops way down to just 2.2 worst case for the 16kW unit so you aren’t going to be saving the planet 40% CO2 compared with gas. They give a “seasonally adjusted” COP of 3.6 which is hard to check but is a bit more realistic than 4.7 - at that level you would still be ahead on CO2 but only by a shade over 20%.

I note they are fairly candid that the system works best with lower flow temperatures and is not well suited to conventional radiators.

So, in conclusion I think their CO2 claim is “optimistic” rather than actually mendacious.

However while I’m happy to feel all warm and cuddly saving the planet I would like to know whether I’m saving myself money - the UK average electricity price is, apparently, 16.3p per kWh and that of gas 4.2p - a factor of 3.88 - given that seasonally adjusted COP of 3.6 it suggests that a heat pump would actually be more  expensive than gas heating in the UK - I guess that’s why they are pushing the environmental aspect :slight_smile:

Obviously the economics will differ slightly in France and, overall, their 16kW unit looks to have slightly better performance than my WPL16S - but not radically better.

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