@cathoderay I think you should qualify this with Air to Water heat pumps. Air to Air are quite capable of rapid heating for short periods of time in an efficient manner. I spent 2 years with these as my only source of heating and they worked just fine.

They are also a lot cheaper to install than air to water heat pumps.

@bontwoody - good point, I was only talking about air to water heat pumps.

@goody Its unusual for a heat pump to be undersized under the MCS protocols, its usually vastly the opposite. Cant you just swap it out for a bigger one? Seems a shame as you have everything else ready. You should be able to sell the old one."

@bontwoody I'm afraid I don't rate MCS, now or when when I was a gas engineer. An association that doesn't really do anything and uphold anything, when push comes to shove.

When I let MCS know about Hero Renewables their response was, not to do anything! Even later on when we tried to get Hero to come back and sort out the problems and they had been ejected from MCS, MCS said "Although Hero Renewables are no longer MCS certified this doesn't stop them from being able to do work on your ASHP" . What is the point of MCS? On there website "When looking for an installer for your renewable installation you should always look for the MCS certified mark for reassurance that your installer is certified. MCS is a mark of quality, which demonstrates that your chosen installer has adhered to recognised industry standards when completing your installation – highlighting quality, competency and compliance" What a complete and utter joke!

Trustmark and Niceic also offered no help

Three organisations that sound good in theory but in practice, when any problems crop up , they all say sorry we can not help you or direct you to Citizens Advice Bureau!

@goody I couldn’t agree more! I just meant they usually get it wrong in the opposite direction and leave a grossly oversized heat pump 😁

I've had a ASHP for 3 months now and from my own analysis I have these 3 general statements I tell people who ask about the running costs of a ASHP:

1. If you have a house hold battery of reasonable capacity and can buy electricity at cheap rates then there are good savings to be had changing from a Gas combi to and ASHP

2. If you have no battery and run a gas combi for long periods of time and maintain a fairly constant house hold temp then you can probably make a saving moving to an ASHP

3. If you have no battery and run a gas combi for short periods and only heat the house when you need to (mornings & evenings etc) then you are unlikely to save any money moving to ASHP 

Here is my analysis for the last 3 months

My Gas usage for Oct, Nov and Dec for the last 4 yrs with cost based on my current gas price of 5.9p kWh

(I ran the combi like statement 3 above note: I cut back even more in 22-23 during the energy crisis)

 Here is my ASHP costs based on the standard elec tariff 24.4p kWh and my Actual cost backs up statement 3. and 1.

(This is running all day and off for around 5-6hrs over night)

And here is what a modern efficient gas combi (94%) would costs to produce the same heat as my ASHP which backs up statement 2.

These are obviously just general statements and there are more efficient ASHP installs then mine as I only have radiators but I think they would hold true for a large number of cases. 

just my 2p worth.

Ian

Edit I had cropped off the totals on the first pic. Also just to note there are no standing charge costs included above.

Posted by: @irmartini

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1. If you have a house hold battery of reasonable capacity and can buy electricity at cheap rates then there are good savings to be had changing from a Gas combi to and ASHP

2. If you have no battery and run a gas combi for long periods of time and maintain a fairly constant house hold temp then you can probably make a saving moving to an ASHP

3. If you have no battery and run a gas combi for short periods and only heat the house when you need to (mornings & evenings etc) then you are unlikely to save any money moving to ASHP 

 

That's really good and simple.  Obviously a gross generalisation but inevitably so if its going to be simple!  I might well use this when talking to people about ASHPs, which i do from time to time.

Personally I'm in category 2 and, based on 2 months of operation, expect to make a modest saving.  It needs a bit more time to be certain though! 

I cant make the business case for a battery stack up until the prices come down about 20% so wont be moving to category 1 yet unless there is a special offer.  I cant currently see the environmental case for a battery hence why this decision rests solely on the business case.  However as solar becomes more common, @transparent has provided a reason why there will be a better public interest case than there is at present and battery prices will hopefully fall (perhaps depending on which dodgy regime gets control of the mineral resources).

Posted by: @jamespa

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Posted by: @irmartini

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1. If you have a house hold battery of reasonable capacity and can buy electricity at cheap rates then there are good savings to be had changing from a Gas combi to and ASHP

2. If you have no battery and run a gas combi for long periods of time and maintain a fairly constant house hold temp then you can probably make a saving moving to an ASHP

3. If you have no battery and run a gas combi for short periods and only heat the house when you need to (mornings & evenings etc) then you are unlikely to save any money moving to ASHP 

 

That's really good and simple.  Obviously a gross generalisation but inevitably so if its going to be simple!  I might well use this when talking to people about ASHPs, which i do from time to time.

...

I also like that simple summary very much. It does, however, also remind me of something else that tends to be forgotten; hot water tanks.

One of the significant reasons for people having a combi boiler is that they don't need to have a hot water tank. That could be because their property simply doesn't have anywhere to put such a tank or it could be so the space can be freed up for some other use. Either way a lot of properties don't have a cylinder in place at the moment and would have to find space for one in order to ditch the combi and move to a heat pump. Admittedly air to air heat pumps can still be fitted but in that case the boiler would have to be retained and used in parallel unless the home owner had a masochistic preference for cold showers.

As has been said before, not all use cases come out with a heat pump as the best option. 

As grossly over simplified those statements are when chatting I think of them as the first hurdle, rather than a final go nogo recommendation on ASHP:

If you align with 1 or 2 then proceed to the next step looking into ASHP in more detail. (As we all know there's lots more detail to go into)

If you align with 3 then its probably not worth your time.