On 01/10/2020 19:52, Andy Burns wrote:
alan_m wrote:

Andy Burns wrote:

The electricity costs for a heatpump will be about 85% of the cost
for mains gas, but the installation costs are much higher.

Is that figure for ground sourced or air sourced heat pumps?

ground source.

From my back of envelope previous investigations, an air sourced pump
can give 3kW thermal energy for every 1kW of electricity but as the
outside temperature falls to 0C this efficiency also drops to more
like 2KW thermal per 1KW.

yes COP falls with temperature, but 1m below ground coils don't get as
cold as air, unless coils are undersized and you end up freezing the
ground by over-extracting.

The only person I have met that had one installed in domestic premises
was bitterly disappointed with the running and servicing costs. In
theory they should have been ideal customers being retired and at home
all day but they were sold a pup. It cost more than fuel oil to do the
same heating job (back when oil was still expensive pre-Covid).

Radiators all had to be replaced with big ugly things to cope with the
lower working temperature so it wasn't a cheap or simple installation.

Installing an EFFECTIVE heat pump system also depends on the level of
insulation in the home

as I said, poke some answers into the calculator.

It needs the home very well insulated or your are burning money.

It may work extremely well for a new build where you can specify the
quality of the build and insulation.

Can still be marginal ...

Air source can work except in the coldest weather but again unless the
house is very well insulated it quickly gets expensive to run. I know
someone with it who is quite happy - highly insulated new build.

--
Regards,
Martin Brown