Posted by: @jo2255

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Main concern is heat geek numbers dont add up for radiator suitability and 5kw heat pump sizing. 

Agreed given what you have said, although Im still struggling with 7kW for a 2004 140sq m house (mine is 1930s 200sq m, partly upgraded to perhaps 2004-2010 standards, 7kW)

BG seems better value assuming all else is equal.  Have you confirmed they are not fitting a buffer or external controls?  I wonder why Octopus are fitting the Daikin not their own Cosy.  I presume they would not fit a buffer or external controls but worth checking if you are considering them.

The 9kW Daikin proposed by Octopus would worry me somewhat.  Its actually the 14-16kW downrated in firmware (unless they have changed their models recently) so is really seriously oversized.  Personally I wouldn't consider this without a bit more thought! and assurance.  Everything you and the surveys tell us would suggest that the 8kW Daikin, which is actually an 8kW machine at heart, would easily suffice.

@jamespa 

Not considering octopus as I do not agree with their heat loss, in addition they want scaffolding, asbestos survey as well as can only fit maximum 200l cylinder. 9kw would be quite oversized for me.

Incase my heat loss actually does turn out to be lower, the new 2026 vailant plus 7kW units can modulate quite low

Inclined towards British gas. They have confirmed no buffer. Intially they had added a 25l volumiser but later confirm not needed as almost all radiators are going to K2 so water volume isnt an issue. 

Posted by: @jo2255

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@jamespa 

Not considering octopus as I do not agree with their heat loss, in addition they want scaffolding, asbestos survey as well as can only fit maximum 200l cylinder. 9kw would be quite oversized for me.

Incase my heat loss actually does turn out to be lower, the new 2026 vailant plus 7kW units can modulate quite low

Inclined towards British gas. They have confirmed no buffer. Intially they had added a 25l volumiser but later confirm not needed as almost all radiators are going to K2 so water volume isnt an issue. 

 

 

Noted.  I updated my post, probably crossing yours, with some negative comments about the 9kW (actually 14-16kW) Daikin Octopus proposal but seeing as you arent considering it they arent relevant!

A volumiser is fine, but if they dont think its necessary then nothing to worry about.  The Vaillant is a sound machine and the controls very flexible.  

@jamespa 

Thank you. Appreciate your response 

Just curious as to what would happen if I had gone with the heat geek proposal for 5kW plus with no radiator changes(not planning to but curious as engineer by profession and need closure)

Most days would be fine i believe. In my area there were 41 days that would potentially require defrost last year.

So the heat pump curve would be set high and radiators would be running at higher temp.

On a cold day house would just not stay warm and defrosts/dhw reheat would make the situation worse I'd imagine as no backup heater as such on the Vaillant unit

Posted by: @jo2255

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@jamespa 

Thank you. Appreciate your response 

Just curious as to what would happen if I had gone with the heat geek proposal for 5kW plus with no radiator changes(not planning to but curious as engineer by profession and need closure)

Most days would be fine i believe. In my area there were 41 days that would potentially require defrost last year.

So the heat pump curve would be set high and radiators would be running at higher temp.

On a cold day house would just not stay warm and defrosts/dhw reheat would make the situation worse I'd imagine as no backup heater as such on the Vaillant unit

I cant really comment on what might have happened as I dont recall anyone posting about invoking the Heat Geek Guarantee so dont know how it works in practice.

The Vaillant does not, SOFAIK, have a backup heater by default, this is an add on I believe (unless they have incorporated it into their 2026 model - which seems unlikely but is of course possible),  You shouldn't need it though unless the gulf stream fails during the lifetime of the heat pump, in which case you (and all of us) will have more serious issues to worry about than being a bit cold.  Of course some in power tell us that climate change is all a hoax, so none of us need worry about that, but they are mostly billionaires so they dont have to worry at all!

Hi everyone! Hope Im not posting in the wrong post, but this seems to be the most relevant for my situation as well! And I could use some help

Just had a HG heat loss survey, and got the results.

- No flow temperature being mentioned anywhere. Better ask the installer who came out or message HG?
- Surveyed heat loss: 6.3 kW turned out to be better than the estimated time 6.88kW was. 
- They say I need to replace the hot water cyilinder
- House is a 1998, well insualted, (cavity+ 10mm loft insulation) 110m2
- I have a 6.7kW Pv array along with a (13.5kw) Tesla Powerwall 3 

now where I could use a little help is the options I've got. and see if pricing is correct (I'd like to stick to Vaillant)

Cheapest option would be
- 5kW aroTHERM PLUS along with a
- uniSTORE Pure 175l Slim cylinder.
- and 0-2 radiator change included
- 340- 370% guaranteed efficiencey
- £5,200 after BUS

Based on previous posts its not only me thinking the numbers doesn't add up....

next up:

- 7kW aroTHERM PRO along with a
- uniSTORE Pure 210l Slim cylinder. // not sure why no option to chose the 175l mode, which would be sufficient for me
- and 0-2 radiator change included
- 340- 375% guaranteed efficiencey // negligible difference? 
- £5,850 after BU?
// still this seems to be the best option>

or
- 7kW aroTHERM PLUS along with a
- uniSTORE Pure 210l Slim cylinder.
- and 0 radiator change included
- 340- 345% guaranteed efficiencey
- £5550, after BUS

and Im not too happy with the placement either. the best spot would require 15-20m extra piping all the way up on the wall into the loft, and then to the cyilinder. which cost extra £3,000 is that realistic? 

Also just checked these ASHPs are around £4-4500 the cyilinder £1500 (definitely cheaper for the installer), is the installation, electrics and pipework, replacing 2 rads really £6000 for 4 days of work?
Octopus just installed their 9kW cosy in my close relative's home, same work, new cylinder, and a lot of extra outside pipework, insulated, no rads replaced, was £3200 after BUS. seems like a huge difference for me

I would appreciate any help, thank you kindly!

@franszo, welcome to the forums… you’re certainly in the right thread, and I can see why you’re struggling to choose between these options, because there are quite a few differences being presented without much explanation of what they actually mean for you.

On the missing flow temperature, I’d contact the installer who surveyed the house and copy Heat Geek in, rather than leave yourself passing messages between them. @JamesPa’s original advice earlier in this thread still seems the sensible starting point… simply ask them to provide it. I’d want the design flow temperature and the outdoor temperature it relates to for each option, so you can see whether you’re comparing broadly similar designs or different compromises. 

On sizing, Vaillant’s model labels don’t mean the machine delivers exactly that output in every set of conditions, so the comparison needs to use the precise model’s available output at your design outdoor temperature and the water temperature your radiators will require. The useful question is simply: “Can you show me how this particular unit meets our calculated heat loss on the coldest day you’ve designed for?” 

The efficiency ranges would probably be my next question, because all three start at 340%, while the upper figures vary. Are you being guaranteed the lower figure at the price shown, or does the higher figure correspond to additional work and a different price? Heat Geek describes its guarantee as covering combined heating and hot water efficiency over 12 months, subject to its terms, so I’d want one clearly stated guaranteed figure for the exact package you’re considering, alongside any higher predicted performance. There’s been a lot of speculation about the validity of this guarantee. Until that is clear, I wouldn’t attach much importance to the difference between 370% and 375%, particularly when the radiator allowances are different too. After a survey, I’d also want to know which radiators would actually be changed in each priced option, rather than being left with “0-2”. I’ve been sent cases by homeowners where the rads in question haven’t specified. 

On cost, I’m finding some of the labour and installation figures increasingly difficult to reconcile myself, and I’m seeing noticeably higher amounts in other quotations homeowners send me for a broad sanity check. However, four days on site isn’t enough information to judge the labour charge… two people for four days is eight person-days, three people is twelve, and the electrician, survey work, design and follow-up may sit outside that period. Equally, subtracting the heat pump and cylinder prices from the total doesn’t leave a figure that is entirely labour, because there are still the other materials, controls, radiator work, electrical components and business overheads to account for. That doesn’t make any remaining number automatically reasonable, but it does mean I’d want to understand what is included before treating it as somebody’s four-day wage.

For nothing more than context, an installer that occasionally subs out to a large installer company collected over £800 worth of left over copper pipe from two installs, which were naturally factored into the price.

Assuming the quotes include a £7,500 BUS discount, you’re looking at roughly £12,700-£13,350 before the grant, rising to £15,700-£16,350 with your preferred location. That is a substantial project, and I think asking for a clearer breakdown is entirely reasonable. I’m not talking about demanding the installer’s purchase invoices or interrogating their profit margin, but they should be able to explain the major work, how many people are expected on site and what the installation allowance actually buys. I have no objection to paying properly for expertise, but I struggle more when the expertise, labour and everything else disappear into one large unexplained number.

The additional £3,000 for the location would certainly make me pause, although I wouldn’t judge it simply as the price of another length of pipe. If the extra 15-20 metres describes the route rather than the combined pipe length, that could mean 30-40 metres of additional flow and return pipe, with insulation and protection, potentially more cabling, wall penetrations and whatever access is needed to work at height. Again, I’d ask them to show exactly what the £3,000 adds beyond the work already included, and to confirm that the longer route has been allowed for in the design and quoted performance, and does that include larger circulation pumps.

I’d query the cylinder choice too. Vaillant does offer both 175 litre and 210 litre versions in the slimline range as far I know, so I wouldn’t assume the larger cylinder is unavoidable simply because you’ve selected a larger heat pump. There may be a perfectly sensible reason involving your hot water requirements or how the cylinder will be reheated, but I’d want that explained, along with why the existing cylinder cannot be retained. “This is the package the system offers” wouldn’t be enough of an explanation for me. 

Your relative’s Octopus installation is a useful comparison, but I’d be cautious about treating it as proof that yours is overpriced without seeing both scopes of work. What I would do is obtain another quotation from a Vaillant specialist for your house, using the location you actually want and a clearly defined cylinder and radiator specification, because that would give you a much stronger comparison than two different systems in two different properties. One small detail worth checking first… you’ve written 10mm of loft insulation… is that a typo, and has the correct depth been recorded in the survey?

My instinct would be to settle the location and get these explanations before choosing between the packages, because at the moment you’re being asked to choose between prices and overlapping efficiency ranges without quite enough information about the finished system. The more expensive option may be worth every penny, but the proposal should make it possible to understand why… you shouldn’t have to reverse engineer it yourself.

Posted by: @franszo

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Just had a HG heat loss survey, and got the results.

- No flow temperature being mentioned anywhere. Better ask the installer who came out or message HG?
- Surveyed heat loss: 6.3 kW turned out to be better than the estimated time 6.88kW was. 
- They say I need to replace the hot water cyilinder
- House is a 1998, well insualted, (cavity+ 10mm loft insulation) 110m2

Thanks for sharing.

We used HG, we found the installer and got him for the heat loss survey. HG tools and processes do not share flow temp in the initial stages, I think I only had at commissioning. They do guarantee a minimum SCOP, which is better than stating a design flow temp.     

We found the HG heat loss figure inaccurate (based on estimated loss from gas boiler usage). 

If you already have a non vented hot water cylinder, it may not need replacing. The HW cylinder is usually not warmed to the same level by a heat pump, but you can do and then it performs like the current one.  

Also, I assume you mean 100mm loft insulation - depending on the material, an additional layer may help. 

Posted by: @franszo

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and Im not too happy with the placement either. the best spot would require 15-20m extra piping all the way up on the wall into the loft, and then to the cyilinder. which cost extra £3,000 is that realistic? 

Also just checked these ASHPs are around £4-4500 the cyilinder £1500 (definitely cheaper for the installer), is the installation, electrics and pipework, replacing 2 rads really £6000 for 4 days of work?
Octopus just installed their 9kW cosy in my close relative's home, same work, new cylinder, and a lot of extra outside pipework, insulated, no rads replaced, was £3200 after BUS. seems like a huge difference for me

We are happy with Vaillant but would have also been happy with the Cosy (except they did not wall mount). 

3k for the extra pipe run seems steep, but perhaps it's scaffolding etc adding to the cost.   

The HG price seems on the right ballpark or slightly high but there can be variation depending on their demand and location.. We hired our plumber to do some rads and also had a nice price from our HG installer for one rad....  

@batpred I would agree with your comment about flow temperature. The industry has latched on to this because a lower flow temperature results in a higher SCOP. The reverse is also true: a higher guaranteed SCOP is based on a lower flow temperature.

With my HG installation, I went for a minimum guaranteed SCOP of 4. The MCS Certificate confirms this to be the case at a max flow temperature of 45C.

The deciding factors for me were good installation feedback, and the guaranteed minimum SCOP. Irrespective of what is in a survey proposal, Ì am not aware of any installer other than Heat Geek that offers a performance guarantee.

I had similar concerns about the performance of one of my radiators at a gas flow temperature of 50C. It struggled to keep an open plan kitchen at the set temperature on very cold days. My Heat Geek installer looked at the K2 that was in situ and he upgraded it to a K3 as a customer option in the Heat Geek survey. I got him to agree to move the kitchen radiator to my dining room. Both these changes were a given before the HG survey was run. The survey came out at a £1700 cost to me (which included the two radiator changes) with a minimum SCOP of 3.7. Increasing the minimum SCOP to 4 (involving 5 new radiators and switching the lounge radiator to a main bedroom) cost another £1200.

We kept our existing Worcester Bosch unvented cylinder (£2000 to change) and it is producing an average efficiency of 3.2 (including the weekly disinfection cycle).

Amazing information both @editor @batpred, I 'll shot HG an email immediatly with all questions, and also booked a survey with Octopus too, which is unfortunately in a month time, but will see. Be back once I have more info! 

Appreciate the help!

@franszo please keep us posted on HG's feedback. Very interested to hear what they say.

Posted by: @l8again

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... My Heat Geek installer looked at the K2 that was in situ and he upgraded it to a K3 as a customer option in the Heat Geek survey. I got him to agree to move the kitchen radiator to my dining room. Both these changes were a given before the HG survey was run. The survey came out at a £1700 cost to me (which included the two radiator changes) with a minimum SCOP of 3.7. Increasing the minimum SCOP to 4 (involving 5 new radiators and switching the lounge radiator to a main bedroom) cost another £1200.

That makes sense, even if few people would have a higher outlay before committing. I ended up having the rad upgrades not factored in their performance guarantee (with the benefit of having chosen the rads). I guess that was also only possible with knowledge of the heatpump considerations - learnt in this forum and elsewhere. 

The way that you sequenced it, you got them to guarantee a higher SCOP!