Octopus Heat Pump

[BazyleParticipant @bazyle]

Even 60 years ago in Africa it was normal to have window mounted self contained aircon units which did have a heat option too. We had one in each bedroom in specially knocked out holes, and they ran all night. Loft insulation hadn’t been invented. I think before that we did have a ceiling fan but it wasn’t used because it blew the mosquito nets about. With sealed rooms and aircon you also didn’t need the nets after spraying under the beds for bugs.
There are a few of these window units about but beware most adverts are just cons for fans placed by the window in the picture. Proper ones heat or cool. I think one of thee would be the ideal solution for a workshop and have seen one intended for caravans with just 1KW output, 300W input.

[Michael GilliganParticipant @michaelgilligan61133]

???

https://www.arcthermal.co.uk/products/air-to-air-heat-pump-monobloc-white-305kw-230v

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https://arcthermal-web.s3.eu-west-2.amazonaws.com/files/etherma/et-hp-fire-ice2-5-w-48001-en.pdf

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https://www.survivefrance.com/t/monobloc-heat-aircon/44596

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[Vic]

On Vic Said:

Just as a point of interest. I picked the brains of an acquaintance last year about Air Conditioning as until very recently he was a consultant in the industry. One thing he mentioned was not to forget you can use AC units for heating as well as cooling. He said his own use at home is 80% heating 20% cooling. The installer also mentioned the cost advantage of using our AC unit for heating over our GCH. We only have the AC in our lounge but we have used it for heating a couple of times. Now we have solar panels and a home battery we may try using it a bit more.

To be pedantic, no, you can’t use an air-conditioning unit to heat. It’s air to air heat pumps that can act as heating or cooling. It’s just semantics but that is generally considered how to differentiate them. Fundamentally they are the same, two heat exchangers and a compressor. The heat pump allows either heat exchanger to be the source (cold end).
You get about 3kWof heat for every kW of electricity put in with a heat pump in heating mode

[Martin Johnson 1Participant @martinjohnson1]

We are on our second heat pump, having put one into our last house as well.  Several comments:-

To run a heat pump efficiently you need to run the radiator water temperature as low as possible.  So first thing is you will need to up your radiator sizes.  Typically put in a double convector in place of a single.  Or think longer, higher or add an extra one.  That cost us about as much again on the £7.5K grant.

Next thing is that you need to be running the heat pump 24/7.  Your house loses heat 24/7 so forget about only running the system mornings and evenings.  Total change of mindset needed.

We use an economy overnight tariff (economy 7 in the old days).  Ii am very suspicious of the heat pump tariffs that will restrict your running hours – see above paragraph.

If you are not wedded to ga cookers, get the gas taken out and save the standing charge.  Also note that in the last two price cap changes gas has gone up more than leccy.

Hope tha above helps.

Martin

[Michael GilliganParticipant @michaelgilligan61133]

It all helps, Martin … thanks

The offer from Octopus came ‘out of the blue’

… it’s time-limited, so I need to focus my mind and make a decision

… hence the question to the forum.

 

The really big factor for me is the price of Oil

MichaelG.

[Bazyle]

On Bazyle Said:

Even 60 years ago in Africa it was normal to have window mounted self contained aircon units which did have a heat option too. We had one in each bedroom in specially knocked out holes, and they ran all night. Loft insulation hadn’t been invented. I think before that we did have a ceiling fan but it wasn’t used because it blew the mosquito nets about. With sealed rooms and aircon you also didn’t need the nets after spraying under the beds for bugs.
There are a few of these window units about but beware most adverts are just cons for fans placed by the window in the picture. Proper ones heat or cool. I think one of thee would be the ideal solution for a workshop and have seen one intended for caravans with just 1KW output, 300W input.

Most older aircon units with heating capability just had a fan heater element built in. Not the same thing.

Even our clothes dryer is a heat pump type. Cheap to run, no condensation and gentle on the clothes.

[Michael Gilligan]

On Michael Gilligan Said:

[…]

 

The really big factor for me is the price of Oil

800 litres cost  £676.62 on 07-March-2025

800 litres cost £1139.04  on 07-March-2026

There were other purchases between those dates 🙁

MichaelG.

[BazyleParticipant @bazyle]

As an alternative to larger radiators a model engineer might arrange small fans to increase the airflow over them. This opens up the opportunity to better control the room the heat is needed in and using water from a heat store down to a lower temperature. In simple numbers a cubic metre of water holds 1KWh of heat per degree so a tank gong from 35C (heated by the pump on economy 7) down to 25C could tide you over until the solar panels got  up to power and again in the evening.

[Michael Gilligan]

On Michael Gilligan Said:

It all helps, Martin … thanks

The offer from Octopus came ‘out of the blue’

… it’s time-limited, so I need to focus my mind and make a decision

… hence the question to the forum.

 

The really big factor for me is the price of Oil

MichaelG.

Our first one went in a house heated by lpg gas.  If you replicate our experience its a no brainer from the financial viewpoint.

Others have mentioned need for good insulation.  Agree.

Need for somewhere to put a pressurised hot water tank, buffer tank and accumulators.  Yes, it can be a pain.  Less so with modern gear, but we have just filled an airing cupboard with plant in our new house.  Very little space to air the washing now.  Our present abode was on town gas but we still went for ASHP, not for the money saving but the improved comfort.

Do shop around for other suppliers than Octopus, but beware of honest John the plumber.  You need a contractor that knows what they are doing and how to size the ASHP.  If you get it wrong you cant just turn the wick up as with a boiler.

Martin

[Michael GilliganParticipant @michaelgilligan61133]

Wise words, Martin … Thank You

Today has not gone well:

Having received no reply to my eMail question, I ‘phoned the Octopus and was offered a call-back ‘by someone technical’ at 14:00

… so far, so good … but there was no call

‘phoned again at about 15:00 and after 20 min on hold was informed that they were all in a meeting until 15:30 but ‘Henry’ would call me when they finished.

I gave-up waiting at 17:00 but couldn’t shout at anyone because all the lines were closed !

”POETS DAY” … I’m not impressed

MichaelG.

 

[Martin Johnson 1]

On Martin Johnson 1 Said:

Do shop around for other suppliers than Octopus, but beware of honest John the plumber.  You need a contractor that knows what they are doing and how to size the ASHP.  If you get it wrong you cant just turn the wick up as with a boiler.

Martin

The converse is also true. The ‘surveyors’ have a very strong tendency to pick the easy route and vastly over estimate the actual heat loss of houses. I ended up with a 6kW unit when my calculations (based on actual measurements and energy consumption records) said that a 4kW unit would have plenty of headroom (2kW was our actual average consumption during the coldest parts of the years). I’m still pretty pissed off about this, since the unit we have is working at the very bottom of its capability rather than comfortably within it.

What I’m saying is:- Don’t rely on Octopus or any other supplier to  do the heat survey. Contract for an independent one and include actual air leakage measurements rather than the back of a fag packet guess that the suppliers rely on.

It’s a lot of money and a long term investment. Getting it right to start with will have a better rate of return than having an easy life for the salesman does.

You should get a good saving over oil.

[Martin Johnson 1Participant @martinjohnson1]

It can go both ways Mark.  You end up with honest John that quotes a tiny unit that is small & cheap but useless.  Or you put your trust in somebody else’s sums.  It certainly is good policy to keep an eye on their assumptions like air changes as you mention; under floor and cavity wall insulation can be complete unknowns.  I don’t think there is a huge incentive to over size the unit, as the labour and other materials form a big chunk of the cost and the cost of the ASHP is just money transferred through the contractor – not much profit in that.

Always remember you have to cover the coldest, windiest day!  The rest of the year it will be ticking over.  I think 6kW for a typical house is about right.  Also remember that you need those calculations to check that your radiators and pipes can deliver the heat at way less than the T50 nominal rating.

Martin

[Martin Johnson 1]

On Martin Johnson 1 Said:

Always remember you have to cover the coldest, windiest day!  The rest of the year it will be ticking over.  I think 6kW for a typical house is about right.  Also remember that you need those calculations to check that your radiators and pipes can deliver the heat at way less than the T50 nominal rating.

Martin

I should add that I’d been running my boiler at 40 and 45°C flow temperatures in order to gather data. 😀

As I said get an independent, professional, heat loss calculation.

[Mark Rand]

On Mark Rand Said:

As I said get an independent, professional, heat loss calculation.

Sorry to say, Mark … I think that would be futile in my circumstances.

Over the next couple of years, I expect to gut every room in the silly little house …  install whatever insulation I reasonably can, and change the whole heating arrangement

That’s why I’m seeking some clarity from Octopus !

I need to work backwards from what it has actually cost to keep the place just-about habitable, by burning oil … I have four years data already.

MichaelG.

[duncan webster 1Participant @duncanwebster1]

As the object of central heating is to warm the air in the house, I would think it better to have an air to air heat pump.  To make radiators work you need them to be hotter than the inside air temperature by quite a bit, so the coef of performance must be lower than air to air. More difficult to retro fit of course unless you have a bungalow

[Michael GilliganParticipant @michaelgilligan61133]

Fair points, Duncan

I have a small, and very badly designed, Dormer Bungalow … so it will be mix’n’match for me.

MichaelG.

Edit: Hopefully that goes some way to explaining why I am asking Octopus the question about ‘minimum installation’

[Nigel Graham 2Participant @nigelgraham2]

Notice this site is now being infested by ads for heating systems made by cephalopods….

[Michael GilliganParticipant @michaelgilligan61133]

?

There are no such Ads visible on my iPad, Nigel

MichaelG.

[Martin Johnson 1Participant @martinjohnson1]

Aanother point worth checking is the location of approved service agents for your favoured brand of heat pump.  We had a Panasonic in highland Scotland installed by a fairly local agency.  However they went belly up leaving us to get service technicians from the central belt.  You can guess what 300 miles of driving did to the service bill!

So make sure there is reasonable few agents in your area.

Martin

[Michael GilliganParticipant @michaelgilligan61133]

Progress at last …

I’ve just had a long, and very useful, telephone conversation with Henry from Octopus.

Survey is now booked for 13-October

Meanwhile, please keep the comments and anecdotes coming !

MichaelG.

[Dave WoottonParticipant @davewootton]

It is worth looking at more than one installer, we gave up on Octopus as we were gutting and refurbishing a 50’s bungalow with no existing wet heating system. Octopus’s answer was to tell us to get a local plumber to install a wet gas fired system and they would then remove the boiler and fit a heat pump and heat pump rated hot water storage tank, and we would then get the grant! No, I didn’t believe it either and we obviously declined.

We then went with a more local company to install both heat pump and wet system and solar panels/ battery, once the solar panels were up and running they then told us all their heat pump qualified engineers had left to go to a rival firm and would be unable to complete the heat pump part of the contract. This was nearing last Christmas and we were living in a motorhome on the drive!  Finally we got lucky and by recommendation found a local company who were absolutely brilliant, sadly they only cover the Lincoln/Newark area. both Octopus and the other company had told us repeatedly that we could not use the cast iron looking hospital radiators on a heat pump due to the low flow temp. This company said no problem and quoted for specialist cast iron appearance radiators finished in the colour of our choice. We expected this to come at a premium price but the quote was only about £100 more than the first installer. Installation went without a hitch, the visible pipework under the rads is incredibly neat, and nine months on all seems well. We went for a Vaillant ASHP on the recommendation of a friend in the trade who also recommends Mitsubishi. All was finished just in time for Christmas, so if you are in the Lincoln area can’t recommend Glow heating highly enough. In all these shenanigans we had to apply for the grant twice but fortunately it was approved very quickly the second time.

Moral of all this is don’t give up, Octopus definitely like to give the impression they are the only ones who can get the grant easily, but we found this to be false, our approval came through quickly both times.

Good Luck

Dave

[Michael GilliganParticipant @michaelgilligan61133]

Glad it worked-out well for you, Dave

Unfortunately it’s quite a way from Lincolnshire to North Wales

After a bad start last week …  my discussion this morning, with Henry, was very encouraging so I’m giving Octopus a chance to survey & quote.

My decision will be largely informed by the reaction of their Surveyor to the ‘Shipwreck’  that I am living in !

Henry has been told, in no uncertain terms, that I have about two years work ahead of me, just to get the place efficiently insulated.

Hopefully they will quote for a Heat-Pump and a Hot-Water cylinder as a simple drop-in replacement for my Oil Boiler … and then leave me to get on with the dirty work of upgrading this little 1963 dormer bungalow.

MichaelG.

[Martin Johnson 1Participant @martinjohnson1]

Our second ASHP is a Vaillent.  Pleased thus far but still have  a winter to do.

Many installers will apply for the grant on your behalf but it is not essentiaal.  However to get the grant your installer must be MCS registered.  See the list here:

https://www.gov.uk/guidance/find-a-

However the technical threshold for getting registered must be pretty low IMHO so do your own due diligence as well.

Martin

[Michael GilliganParticipant @michaelgilligan61133]

Oops … this is rather unfortunate

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MichaelG.

[Grindstone CowboyParticipant @grindstonecowboy]

https://www.gov.uk/guidance/find-a-heat-pump-installer

 

https://www.gov.uk/guidance/find-a-heat-pump-installer

 

Fixed that for you 🙂

Rob

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