When I joined  http://ClimateConcern.yahoogroups.com 5 years ago Ros Mayhew mentioned that he had great hopes for the energy savings that would eventually be made by using heat from the ground. I started to study a subject that was then unknown to me and started an experiment of renovating our 1965 house for the 2050s.

This included ground source heating and heat recovery ventilation. I hoped people might be able to learn from my mistakes so I am writing a book about it.

In the process I am amazed by the variability in the efficiency of heat pumps. An excellent web site provides a mine of information on this.

http://www.waermepumpen-verbrauchsdatenbank.de/index.php?lang=en and the supporting pages paint a remarkable picture of variations in the coefficient of performance (COP) which need to be eliminated if heat pumps are to reach their potential for energy saving.

This shows the variability of Air Source in 2010 from 1.27 to 4.92 COP based on 55 heat metered volunteers. This is incredible as Air Source, your old air conditioning, has been around for yonks!

Ground source heat pumps have still been around for 20 years, have a higher potential, but show a variability between 1.84 and 5.61 based on 78 heat metered volunteer owners.

If the higher figures became commonplace the cost of domestic heating could be halved!

There is lots of information here to identify best practice. 22 ground source pumps from 14 manufacturers logged performances above 4.5 for 2010. The best was a single Hautec HCS PN 48 closely followed by a Dolder ZR18 LG 5.0, a Weider SW90 an Eigenbau and a Nibe Fighter 1140-12.

The Veissman Vitocal 300-G appeared 4 times in the group with performances between 4.59 and 4.88. This model well outperformed earlier Veissman models so improvements are still being made. Looking into the detail there appeared to be no efficiency gain with size of installation or size compared with size of house but more could be done on this.

We are at the stage of early motoring when hill climb events enabled owners to compare performance and identify winners. We need a worldwide heat pump club that will achieve similar improvements. Is this it or is there another?

Malcolm