I’m looking to buy a house which has a ASHP installed; I’m wondefring what I can expect in terms of savings, and what I need to check before signing on the dotted line, for example, will the radiators be big enough, how can it be used in conjunction with a gas boiler (if at all) and solar panels.

Basically, I’m looking for some simple basics from folk who have practical experience.

ASHP are fine, savings will depend how you use it and how well it was installed, what make it is and how it is controlled.

If design was done properly the radiators should have been sized according to the designed flow temperature. But the pipework would have to be also sized accordingly.

Not all ASHP are equal, not all installers are competent.

I work in the industry now and there are several mis-conceptions about them, as a company we have installed heat pumps in buildings ranging from modern through to a castle. They work in all of them but the design is critical.

Whereabouts in the UK is it? That can have a significant impact on efficiency. As bear says, lots of things to factor in including insulation, air tightness, any solar gain the property may get, etc.

You will use a lot more electricity than you think in the winter.

Freddie’s Field

We have one fitted in our house in Tobermory – it was a new build with high levels of air tightness and insulation. We have wet UFH downstairs and radiators upstairs – the radiators barely come one but it’s been a relatively mild winter. It’s nice having virtually instant hot water any time of the day. Electricity bills are the same as our old 4 bed house but we don’t have gas here. Don’t really understand why you’d want a gas boiler if you have an ASHP – added complexity and service costs. Our pump has a 7 year warranty and pretty well doesn’t need servicing – only to vent the expansion tank every year or so.

I am in my second winter with an ASHP, installed on the North Wall of a house in Scotland.

As stated by others ASHPs work but design is more critical than a gas CH system.

They do not normally work with a gas boiler, though I think there are hybrid systems. We removed the gas supply.
We have solar panels however they do not really interact with the ASHP as there is normally not much solar when you need heat.

You should notice large radiators or underfloor heating and large pipes. ASHPs work at lower temperature and higher flow.

We asked a lot of questions when getting ours installed, I would advise making sure you know who installed it, check out the company etc.

As a above you will use more electricity but no gas. Use in terms of kWh will be much lower than gas heating however this will not likely give a cost saving as electricity is more expensive. I’m not sure how the price ratio of the two fuels compares today.

Importantly do not listen only to those who will tell you that ASHPs do not work. They do and like all choices there are pluses, minuses, balances etc.

I like my ASHP and do not regret having it installed.

Savings? Significant compared to direct electric (~300% more efficent).

Pointless if not insulated to a high standard.

Gas? Usually not around.

Rad size? Yep you need big ones.

We are 6 weeks into life in a new build with ashp. Adjusting quickly after 25yrs of mains gas and combi. Surprisingly think we prefer it.

Probably dearer than mains gas (which we haven’t now got so irrelevant) but cheaper than lpg or oil.

You have to drive it differently but that also means we are comfortably warm all of the time. The 2x room stats are just to meet building regs and are whacked on full. Instead it runs off outdoor temperature and a curve that relates it to energy requirement of the house. You then choose an indoor climate level by offsetting the curve on a scale from plus to minus ten. When we moved in it was on plus 6 and we were melting. Now on minus three and comfy. Bedrooms kept a bit cooler with rad stats. Might be able to refine it a bit using the timer to drop the offset further at night, but suspect it is a fine balance between dropping the core temperature too much and having to expend more direct electric rather than air source energy bringing it back up quickly every morning.

No ufh. All rads are pretty standard twin panel convector but nothing huge. High flow and modulated water temperature seems a much more intelligent way of heating than the all or nothing hotter rads of a gas system. Insulation is just to current building regs, but think good detailing of the floor slab, cavity and window apertures etc makes the biggest difference.

Mis-conception no 1, the building doesn’t need to be super insulated

The 2x room stats are just to meet building regs and are whacked on full. Instead it runs off outdoor temperature and a curve that relates it to energy requirement of the house. You then choose an indoor climate level by offsetting the curve on a scale from plus to minus ten. When we moved in it was on plus 6 and we were melting. Now on minus three and comfy.

I live in a new build with ASHP, and I don’t have a clue what you’re talking about 😂

I’m very happy for you 🙂 I’m sure they can be controlled in different ways.

I’ve posted about my ashp fitted to my housing association 1bed draughty/leaky/non insulated bungalow before but I’ll not bore you as to how utterly shit it is, switched it off last year as it was using £40+ electricity/week for buggerall heat output as I still had to light the stove and that was at last years cheap electricity costs, my electricity costs are now less than £8/week. I’m using my stove for all heating and leave it on 24hrs/day as I get free logs, it’s only myself in house so not bothered bout hot water.

In a well insulated house I imagine they’ll be great, in a poorly built 30yr old bungalow it’s nothing more than a greenwashing exercise for the housing association.

Thanks for the comments – quite a range of experience and some good pointers on what to check!!

@dovebiker I am sick with jealousy for your house 🙂

In a well insulated house I imagine they’ll be great, in a poorly built 30yr old bungalow it’s nothing more than a greenwashing exercise for the housing association.

That should never have been installed.

Does anyone have any good links to online or books about this stuff?  I’m interested in installing but I need to know enough to know that my installer is competent.  One person who quoted for our underfloor heating didn’t want to put insulation under the screed because ‘heat rises don’t you know’

Bear – where are you in the UK?

The more I think about it, the more I should be biting the bullet and tackling this now alongside our modernisation of a home (a 300+ yr old stone house n northern Scotland, modernised for the first time in the 80’s that needs work to make it work better as a home and more thermally efficient). As we are on lpg that adds to the motivation to get it sorted.

Putting ufh heating on the ground floor and a ASHP would seem like a win. Are there still grants for this in Scotland?

Following with interest. Some similarities to convert (‘only’ 150+ yr old stone house in Scotland, insulated as much as it can be easily but still not great). Planning an extension involving remodelling of kitchen/utility/removal of conservatory in next 5 years, and a desire to go gas-free at the the same time. Current gas boiler was replaced the month before we moved in 3 years ago so low risk of it falling over any time soon I hope, but have the desire to plan for living without mains gas in future.

Are there still grants for this in Scotland?

The current RHI scheme runs out the end of March – some of the money came from the EU.

I’m just checking through to see if I can apply…

There’s supposed to be a new heat pump grant scheme in the pipeline.

Soma – the problem is not the heat pump but the design of the system. Not big enough emitters and not tackling at least some of the draught / insulation issue, as it doesn’t matter what fuel you use it will be expensive due to losses.
And you may well have had one of the exhaust air heat pumps? If so totally unsuited to your property.
Also suspect housing association put the job out to tender and went with the cheapest……

Roger Bisby on the SKILL BUILDER CHANNEL You tube has 2 interesting videos, 2 things that stand out, location due to noise eg fan and risk of theft, cant remember if he mentions those.

Not sure I agree with the Roger  Bisby stuff.  He seems to be biased against on the basis that they should be cost efficient compared to fossil fuels but I think a lot of people are comfortable with higher cost vs less fossil fuels although they would prefer it not to be that way

but I think a lot of people are comfortable with higher cost vs less fossil fuels

Thats if they have disposable income to pay for the kit and the higher energy costs.

Back in the 60,s blown hot air was the fashion and that failed quite soon, followed by communal heating systems, but they where returning, but lots of residents now hate them due to huge rises in energy costs and freeholder add on costs.

Thats if they have disposable income to pay for the kit and the higher energy costs

Agreed.  But most folks I know are looking to see what they can do to reduce carbon footprint and this is one of the options.  It just has to be looked at alongside other things they can do and then work out the most effective way to use the cash you have

@convert yes interest free home loans and grants are available in Scotland. I just got one for our house.

Find funding

It’s some faff but worth it. In our case we got connected to mains gas but also got cavity wall insulation. Loan interest free over 10 years.

There are options for ashp on there but will depend on your home EPC.

Soma – the problem is not the heat pump but the design of the system. Not big enough emitters and not tackling at least some of the draught / insulation issue, as it doesn’t matter what fuel you use it will be expensive due to losses.
And you may well have had one of the exhaust air heat pumps? If so totally unsuited to your property.
Also suspect housing association put the job out to tender and went with the cheapest……

System is a daiken altherma feeding 3 600mm x 600mm type 22 and 2 1200mm x 600mm type 22 steel radiators with all the gubbins in the attic and wall mount “dumb” Drayton heating controller, you’ve pointed out the obvious flaws that were apparently “obvious” when it was installed 8yrs ago but not “obvious” enough to the housing association who claimed green credentials for removing open fire back boiler systems.

Two months after it was fitted I opened up the fireplace and lined the chimney with a 904 liner and fitted an inset stove (mistake, should’ve gone freestanding) which gave enough heat to raise the internal temps to a comfortable level for living with spms.

Housing association then fitted Tesla power wall battery so I could store cheap/free/paid for off peak electricity then run the house from battery during waking hours to offset the heat pump costs, works well with octopus agile tariff but with electricity costs about to near enough double I’d be paying £70 week in winter for barely background warmth.

Stove wins for sure as I have an unlimited supply of seasoned logs, should’ve fitted a freestanding stove with back boiler but it’s done now and inset stove ain’t coming out without major hassle as there’s 60kg of slate slab bonded to wall holding it in with another 60kg slab for hearth

Ashp can work very well though, mate built his “final” house last year, hauf hous type build but from Ukrainian company (I think) with ashp underfloor heating/ventilation system and special windows. It’s not massive at “250^m” but it’s all open plan and seems huge when inside, very comfortable to be in and half the cost of the ugly shit being built in the area.

Ah Daikin, split unit? bloody awful things currently taking 6 out at a golf club due to their unreliability and in-effectiveness! Also looking at a school with similar units and similar problems!

So my sister is buying a new build with ASHP and she tells me it is a DAIKIN one. Does that mean its going to be rubbish?

Not necessarily, if well serviced and sized correctly for a properly insulated house I see no reason to be worried.

As an aside, A fortnight ago I switched off my heat pump system as it was costing £40+/week for little more than having the benefit of hot water, as it’s just myself in the house I’m not fussed bout having hot water so now my electricity usage has been reduced to less than 5kw/day or <£1.10 per day. More money for beer