First a little background on our situation.
Our property is electrically heated. When we bought the place it was heated by a mixture of night storage heaters and convection heaters. There is no wet central heating, no underfloor heating etc. The only additional source of heat is a 5kw log burner in the main room, Because of this, our electricity consumption is massive, especially during the cold dark months of the winter.
So, in an attempt to make heating our property more efficient, I started to look at air to air heat pumps and booked a visit from a local heat pump installer. During the sales pitch they said that the units had a COP of around 3 to 4 but the manufacturers brochure they left with us clearly showed about 1.25 to 1 at 11 degrees C and less for lower temperature.
This made me a bit wary about claims for this technology so I reached out to the community on sustainability.stackexchange.com (because back then there was no Better Century ) and the nice folks over there pointed me towards some fairly technical research papers. I don’t really understand the research but the impression I get is that the efficiency of these units depends on 2 factors:
- The outside temperature.
- The amount of heat that you want the unit to provide.
This has lead me to the conclusion that they may not be viable for the typical leaky, poorly insulated UK house but that they may work in a well insulated new build.
This is born out by anecdotal evidence from the couple of people that I know that have these units. Apparently the heat exchangers on the back freeze up during the winter if you run them too hard, and then they have to spend energy defrosting the heat exchanger .
Just thought I would share my findings so far on this. Does anyone else have any experience with this sort of heat pump in the UK? Can anyone point to proper data about their effectiveness?