Cutting through all that technical COP talk and moving onto the practical realalities -:
An ASHP customer on Friday told me that the bill for the last quarter for heating her small bungalow via a ASHP was over £400!!
I know it's down to how much money you earn or that you've got, but that's not cheap to me either!
Then add the fact that the radiators take hours to warm up and don't even start to work until the H/W demand is satisfied hence leaving the customers house perishingly cold for long periods of time.
Which proves that Servotech is a plumber (using it in the derogatory sense of the word). Looking at his other posts he does give the impression of having 35 years experience of doing much the same and avoiding looking outside the familiar small box.
That post roughly translates into :
A customer has a poorly specified system, badly designed/incorrectly installed, and it doesn't work very well. Therefore, by completely ignoring design faults specific to that installation, ALL ASHPs are rubbish.
By that logic, because some people have poorly specced and badly designed/installed gas fired heating systems, all gas boilers are rubbish.
As to whether £400/qtr is too high, well I can't really comment on that. But a quick look in my file shows that a one bedroomed flat has been using (on average, over 6 years) about £150/qtr at current prices. That's average - winter will be a lot higher, summer a lot lower. That's a flat without a cold roof, cold floor, or four cold walls. I'd expect a bungalow to be considerably worse as it's possibly the worst shape to make a dwelling - maximum outside area/living space. Is it well insulated BTW ?
Given that no-one has actually claimed even an ASHP will be cheaper than or even match gas for running costs*, I'd suggest those running costs aren't necessarily bad.
As to the system, it sounds like the unit is under sized (that would account for the slow warm up) and the controls haven't been well thought out (priority to DHW rather than rads or split).
Don't get me wrong, I'm not commenting on whether an ASHP was or wasn't a suitable choice for this lady, just that the conclusion that ASHPs are rubbish because this one isn't "right" is just plain wrong.
* It would have to run at a CoP of about 4 to match gas for cost. It'll be considerably less in very cold weather when it's doing the most work.
