First and foremost - whats the running cost for the heating system

@batalto, would you ask for proof? Homeowners can fib.

@editor you could just ask for a utility bill? Doesn't seem an odd question to me to ask a seller.

I would be keen to know who does the systems routine maintenance. If it is the manufacturers agents then at least you know it was correctly installed and setup. At least it is with Mitsubishi: they will not accept a system on a maintenance contract until it has been inspected and tested by their service agents.

Posted by: @editor

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@batalto, would you ask for proof? Homeowners can fib.

I think when we bought/sold a couple of years ago utility bills was one of the questions in the pack from the solicitors.  So there would be some comeback if you were to fib.

The Heat Pump Federation suggests:

• Service history
• MCS handover pack
• RHI history (if applicable)
• Contact details for current service agent (ring and talk to them)
• Heat pump electricity meter readings (can be interpreted to some extent into past efficiency)
• Interrogate the controller (technical assistance probably required)

@abernyte "If it is the manufacturers agents then at least you know it was correctly installed and setup." - you would hope so, but...

We've seen much evidence of manufacturer's agents incorrectly installing and badly setting up ASHPs, which then operate inefficiently, and cost home-owners and occupiers a fortune to run. My install being a case in point, correctly installed per OEM literature, but the OEM installation is not the most efficient way to install a heat pump, simply the easiest way for plumbers and sparks used to simple on/off timed heating controls to install. Then the system commissioned and left running very inefficiently using 3rd party controls rather than the ASHP controller, and climatic compensation disabled.

Evidence of installation & service by the manufacturer's approved installer/s currently does not show evidence of an efficient ASHP install.

@allyfish  I do take your point that this is not a mature market and that third party installers can be found wanting in how some systems are installed and configured. I can only go by my experience (and that of neighbours with similar systems) in that my installation was done by a long experienced renewables installer and then audited by NAPIT who raised no issues.

It was when I applied to the manufacturer for a service contract that it required audit by their agents who carried out an exhaustive check (and actually found a minor plumbing issue which they rectified) and comprehensively balanced and tweaked the system before agreeing to accept the contract and the concomitant risk. If all manufacturers are so diligent then evidence of manufacturers service should give a fair degree of confidence.

Of course internet fora are a magnet for those who are generally less than satisfied as opposed to those who have few or no issues.

Who is the manufacturer?

@derek-m Grant UK in my case. By their own admission, they 'make it easy' for tradesmen used to fitting gas boilers to fit ASHPs. But that does not make for efficient installs or system operation. There's also some work to do in the thoroughness of the commissioning process as well.

This article by Grant, republished yesterday, is factually incorrect.

GRANTUK.COM "https://www.grantuk.com/knowledge-hub/tips-advice/setback-controls-and-heat-pumps/"

Setback controls and heat pumps – what do they do? | Heating Advice - Grant UK

Setback controls enable an air source heat pump to operate efficiently as possible while never being completely switched off. Learn how they help a heat pump to operate efficiently.

The you cannot adjust the ASHP flow temperature into a 'set back' by lowering the room thermostat. The ASHP flow temperature is a fixed parameter, either set at constant temperature or under climatic compensation. It seems Grant's own staff need some training when it comes to how the Chofu ASHPs work. All lowering the room thermostat will do is cause the ASHP to cycle on and off, quite frequently, depending on the type and hysteresis of 3rd party thermostat used to control room temperature. When operating like that, the power consumption is higher as the inverter control never stabilises and is always playing catch up to try and achieve flow set point temperature.

@allyfish 

This is a constant Q for myself, many on the forums state "setback" by 2Deg during the night & day when the house is unoccupied/sleeping.

On the grant aerona 3 unit, I see no way to do this. I go into INST and play with the flow temp - but that is not automatic nor easy nor scheduled. 

Mounted the controller in my kitchen/living area - useful for info - but doesn't adjust the flow either based on internal temperature - not that much of an advantage...