wonderful diagram of an ASP on EDF website

Andrew expressed precisely :

Perfect sense, it is the same principle in reverse as a fridge, freezer or air conditioning.

the large blue arrow could do with pointing the other way

It happens that Andy Burns formulated :

The blue arrow would then need to be red, for heat in. It is sort of logical with cold out, though not the way it works.

The left hand arrow could have been usefully drawn left-to-right.

I suppose your oven heats pies by taking the cold out of them?

Andy Burns explained :

Of course, and my lights are darkness absorbers.

... was the answer that I was hoping for.

Anyone who thinks that a typical property built in the decades that they mention could repalce a gas boiler with a heat pump is living in cloud cuckoo land. You need to spend far more than the cost of an air-to?water heatpump to make the house even vaguely comfortable. They even coyly mention that you may have chenge all the rads for triple-panel ones.

Dark suckers, surely?

Does it explain why they cost so much?

Yep. And the figures the Climate Change Committee used in their recent report for solid wall insulation etc were much lower than estimates for here, even without UFH. Then there's the way the most impressive of them said he'd reckoned the only really safe way to prevent risk from damp was to replace the suspended floor by a concrete floor. Ouch.

I also noticed EDF's casual "So you?ll likely need a bigger hot water tank". What about all the people who don't have a hot water tank at all

- and very possibly no convenient cupboard to fit one. (Many older houses went from Ascots and similar water heaters direct to combis.) It adds a fair bit to the cost if you have to fit a tank in the loft and run pipes.

Andrew laid this down on his screen :

Plus the ridiculously large running costs.

They are saying your DHW won't be so warm. My boiler takes mine to just over 60C for Legionella safety, will ASPs be struggling to do this?

Robert laid this down on his screen :

It can be done, but as internal rooms are not insulated from one another usually, there would be lots of heat loss to unoccupied rooms.

A charged heat store might be one solution for a rapid source of heat output.

The claim is it's about the same for on-peak, with savings if you run it part off-peak.

The bottom line is that maybe it makes sense for new build with UHF, preferrably in a nice big slab for inertia, and with super insulation and draught proofing. Potentially with new build you can include an efficient ground source HX.

But hey, you successfully sell a new religion and people will pay for indulgences.

Because that is what it is. It has its own momentum now and I am not sure that reason is going to stop it. Rather like Brexit.

The GSHPs I've looked at do reach 60°C but run at lower efficiency when the output is at high temperature for DHW, they revert to lower output temperature for UFH.

on 13/12/2020, newshound supposed :

The general accepted figure is 2kw gets you 4kw out. E is around 4x the cost of gas, so my present gas heating cost would double.

If you have a hot water tank (that is warmed up by a heat pump) then a conventional immersion heater will normally be fitted to boost it up to 60C. Not a problem unless you are big user of hot water. Its the fact you will almost certainly need to change your rads to triple-panel ones and spend a lot on insulation too that they seem to gloss over.

I guess they mentioned the typical age range of the target houses to exclude solid-walled houses, though unfortunately the photo of a chap kneeling next to a Daikin heat pump seems to show a house with solid walls going by the brick bond arrangement.

Some have a programmed hour at 60 every (from memory) day - ideally when they can use a cheaper, off-peak tariff for supplementary heating.