Heat pump experiences

[mjr]

The "you need excellent insulation" is code for "this doesn't put out much heat". The insulation would give the same benefit whether you had a heat pump, or an open fire burning £50 notes!

This is true. The maximum output of a heat pump is far lower than the oversize gas burners often whacked into UK homes to cover up the defects and errors in the central heating systems. My ASHP is 8.5kW nominal (it does 12 for short bursts), replacing a 28kW oil burner IIRC. More insulation helps any heating system and getting up to the recommended level often pays back in 3 years or less.

The economic case for going to a heat pump is currently non-existent unless you are on electric-only heating. Even oil-fired CH is comparable to ASHP running costs.

This has been completely not true for my house. It's cheaper than oil despite us now having a more consistently-warm home. The wood burner has very rarely been lit since switching, whereas it used to be almost daily in winter.

There is a running cost benefit with a GSHP, but you are unlikely to recover the installation cost over the life of the system.

I can't comment too much on that but I have seen that GSHP installation costs do seem to vary wildly between sites.

 

[CXRAndy]

My last new build had air source heating. All downstairs was wet under floor, radiators upstairs. I was meticulous with sealing the building and insulation double in the loft. I also fitted a MHVR. It was so cheap to run, zero carbon emissions from the house, everything was electric.

Our next project will have MHVR with Aircon cooling too, high output heat pump

 

[rogerzilla]

We have the option of a GSHP at the next house since it has an oldish oil boiler and 3 acres of largely unused, clear, flat grass. However, a trenched GSHP (the cheapest option if you have space) would be about £17,500 after grant and the annual saving is very small, certainly not recoverable over even a 20 year system life. The house is hard to insulate, with parts dating to the 1700s, and with room-in-roof layout upstairs. There is 200mm of fibreglass in the small lofts, but not necessarily in the large inaccessible bits where the ceilings slope.

If oil prices were a lot higher then it might be worth it, but not at the moment. I like the idea of GSHPs (I don't like ASHPs due to the cold weather performance) but right now we'd pay much more and get less flexibility in return. The other worry with heat pumps is poor installation by cowboys chasing the grants, reliability and parts availability. There are lots of horror stories.

 

[gzoom]

My last new build had air source heating. All downstairs was wet under floor, radiators upstairs. I was meticulous with sealing the building and insulation double in the loft. I also fitted a MHVR. It was so cheap to run, zero carbon emissions from the house, everything was electric.

Our next project will have MHVR with Aircon cooling too, high output heat pump

Did you go for a passive house build? I'm thinking for our retirement we might go for a energy efficient bungalow, probably 150sq meters max, however a LOVE glazing, and glazing LOVES losing heat.

For the current renovation we ordered 50sq of new glazing, that in addition to all the glazing we didn't change, I suspect we are at 30-35% glazing to floor area!!

 

[rogerzilla]

Triple glazing? Get stuff with a 15 year warranty on the sealed units, though. Also, triple glazing isn't recommended, even by the people who sell it, for rooms that get a lot of solar gain. I suppose you could mitigate this with external shutters - something that should really come back with likely hotter summers.

 

[CXRAndy]

Did you go for a passive house build? I'm thinking for our retirement we might go for a energy efficient bungalow, probably 150sq meters max, however a LOVE glazing, and glazing LOVES losing heat.

For the current renovation we ordered 50sq of new glazing, that in addition to all the glazing we didn't change, I suspect we are at 30-35% glazing to floor area!!

No we didn't. I had the house design from 16 years ago with awkward roof design.
We made a quick decision to build it from laying dormant for that period

Had I thought a little more about it, I would have gone for a simple roof and installed solar/battery storage too.

It's an idea for the next project. We keep learning and when we are ready will include the latest energy saving tech. Triple glazing etc

 

[Tenkaykev]

Triple glazing? Get stuff with a 15 year warranty on the sealed units, though. Also, triple glazing isn't recommended, even by the people who sell it, for rooms that get a lot of solar gain. I suppose you could mitigate this with external shutters - something that should really come back with likely hotter summers.

Michael de Podesta has a blog about various things related to heat pumps / insulation et al. He's a real " boffin " ( PhD ) and writes really well. In this article he discusses window blinds, and how he found some at John Lewis that turned out to be really effective. His other stuff is equally informative.
https://protonsforbreakfast.wordpress.com/2025/01/24/insulating-blinds/#comments

 

[rogerzilla]

To keep heat out in summer, the blinds or shutters really need to be on the outside. Once the sunlight is through the glass, it gets absorbed by internal blinds, heating them up, or reflected as longer wavelength IR (the literal greenhouse effect, nothing to do with its climate-related use) which also stays mostly in the house since it doesn't pass back through glass. It's still better to close curtains/blinds on hot sunny days than to leave them open, but it's only partially effective.

 

[Smokin Joe]

I was lucky with mine, there is a scheme in Wales where any household of retired people with one person with a medical condition (Mrs SJ has a disabled badge) can qualify for a completely free installation of an ASHP and solar panels. Next door got one because she has high blood pressure and half the people on our mainly elderly estate seem to have them.

I won't know till October what the cost to run compared to gas will be over a year, but all the indications are that it will be cheaper. One neighbour reckons that with the solar export guarantee he had a zero bill for the three mid summer months.

Had I had to pay for the installation though, I wouldn't have touched it. I'd be long gone before I got my money back. Over time as heat pumps become the norm I can't see any technology there that would prevent the price coming down to what a gas boiler costs.

 

[Milzy]

I was lucky with mine, there is a scheme in Wales where any household of retired people with one person with a medical condition (Mrs SJ has a disabled badge) can qualify for a completely free installation of an ASHP and solar panels. Next door got one because she has high blood pressure and half the people on our mainly elderly estate seem to have them.

I won't know till October what the cost to run compared to gas will be over a year, but all the indications are that it will be cheaper. One neighbour reckons that with the solar export guarantee he had a zero bill for the three mid summer months.

Had I had to pay for the installation though, I wouldn't have touched it. I'd be long gone before I got my money back. Over time as heat pumps become the norm I can't see any technology there that would prevent the price coming down to what a gas boiler costs.

Which Heat pump system? Joule are much better than Kingspan’s as Kingspan’s have the same sized small coil no matter what the cylinders capacity is. Joules get bigger as the sizes go up so are more efficient.

 

[Smokin Joe]

Which Heat pump system? Joule are much better than Kingspan’s as Kingspan’s have the same sized small coil no matter what the cylinders capacity is. Joules get bigger as the sizes go up so are more efficient.

I've no idea. How do you tell?

The brand name is Activeair, if that helps.

 

[rogerzilla]

The green energy sites are currently showing an ASHP as having slightly higher running costs than a gas boiler. Oil is cheaper still right now. A GSHP would be cheaper than gas but installation costs are huge even if you can do horizontal trenches. We have that option at the next house and will look into it but I think (a) it will still cost around £18k after the grant compared to about £3k for a new oil boiler and (b) the equipment will take up too much room in the house.

 

[mjr]

The green energy sites are currently showing an ASHP as having slightly higher running costs than a gas boiler. Oil is cheaper still right now. A GSHP would be cheaper than gas but installation costs are huge even if you can do horizontal trenches. We have that option at the next house and will look into it but I think (a) it will still cost around £18k after the grant compared to about £3k for a new oil boiler and (b) the equipment will take up too much room in the house.

What "green energy sites"?

Also, gas and oil will only stay cheap until the taxes currently unfairly only on electric are shared more properly, and/or they start to run low.

 

[Tenkaykev]

There are many heat pump installations that are online and you can see in virtual real time. You can select the type of property, location, make and model and many more parameters, select the time period going back up to a year with all the input / output available to view.

https://heatpumpmonitor.org/

 

[rogerzilla]

That's interesting. The top one is a GSHP, as you'd expect, but it seems to be a purpose-built house of recent date with underfloor heating and a flow temperature below blood heat. We'd be trying to do it with a house where parts are 18th century, room-in-roof design, a very sub-optimal shape for heat losses (the footprint is like a lower case h) and a huge number of windows.

I'd be interested to know how many of the houses also have a log burner; you can comfortably keep most of the house at 16 degrees if your sitting area has a fire. In fact, in my current 3 bed house I ONLY use one log burner for heating if I'm in all day; the living room is about 22 deg C and other rooms are warm enough.