"The Natural Philosopher" wrote in message
...
G&M wrote:

"nick smith" wrote in message
...

Soil heat recovery systems are even cheeper .............
400% efficient, for each 1 unit you put in, you get 4 out - wow !!

Maybe, but how much real estate do you need and what are the economics
of

a system,

including instal costs to provide a 4 bedroomed detached house with heat

and hot water

year round when oil and gas are available at a cost of 1 or 2 p per kwH
?

I am not saying its bad, just wondering if its economically viable at
the

moment in the UK

Unfortunately installation appears to start at about £8k and work
upwards so
they never get to a payback situation for many users. Problem is you
need a
double stage compressor system if you want hot water and radiators,
whereas
the cheaper units sometimes quoted only supply underfloor and pre-heat
to
the water tank before an immersion heater.

What I really don't understand is why all these units run on
electrictity.
If they used oil or gas the running costs would be under half and they
would
then be economically viable.

Becasue the efficiencuy loss of a small gas engine to run the pumps
cancels out the lower running costs. Fuel cells may ultimately change
that.

They may, but be prepared to wait a long time.