@editor

OVO: 'Sorry, we aren't installing heat pumps in your area just yet'.

eonnext online quote Worcester System: £5,900
eonnext online quote Vaillant System: £5,900
eonnext seems to think I need a 12KW heat pump and a 210 cylinder!

boxt uses the same system for online quotations (zuno.tech) which provides some interesting comparison data
Worcester System: £8,300
Vaillant System: £8,600

A local installed said he installed a system on a similar property and total cost after BUS was £7500

Octopus estimated the heat loss at 7.8kw

£5k
50 deg at -3 design temperature
Cosy 9
180L Cylinder
8 radiator changes

I think this might be the winner, has anyone had a similar install with performance data?

There is a thread here about Octopus Cosy heat pumps - mine is a Cosy 9 with a heat loss of 8.4kW and a 50c design temp at -3.2c.  It's worth noting here that my tribulations are not usual and are being sorted out (I hope!!) In any case, it can certainly show you that the Cosy is capable of sufficiently heating the house.  You will find that you have to run it like a gas boiler with a WC module fitted - that is, with a thermostat controlling the heat draw with a WC controlled flow temp.  It does modulate the pump, compressor and flow temps better than an equivalent gas boiler setup but it will still be heating on/off so positioning of the thermostat is critical.  Any experimentation with running it purely on WC and Flow Temps is down to the customer as it isn't an operating mode that they seem to support.

I'm in two minds about that.  On the one hand, installation and support has been excellent (hmmmm....mostly very good, they still suffer from the "someone will call you back" problems) and the price is beyond competitive.  However, if your driver is uber-efficiency then you really need to be with a non-Octopus install: it's a tradeoff between capital outlay and operational costs.  Efficiency loss is hard to derive but assuming a non-complex install, it would seem you may see a loss of around 0.4 or so in COP.  

Posted by: @andrewj

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 You will find that you have to run it like a gas boiler with a WC module fitted - that is, with a thermostat controlling the heat draw with a WC controlled flow temp.

Does the system force you to use it this way, or is it just that Octopus wont provide any help if you attempt to use it in pure WC mode by increasing the 'set' temperature to well above desired?

Posted by: @andrewj

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However, if your driver is uber-efficiency then you really need to be with a non-Octopus install:

WC is not just about uber-efficiency.  If you get it right it should, or certainly may depending on the house, give a higher level of stability that control based on room temperature.  This is because the response of the house lags the stimulus typically by many hours, which in any control loop can lead to oscillation. 

WC 'gets ahead' of the lag by detecting the fact that the house is about to experience a greater degree of cooling (and thus needs a greater degree of heating) well before this manifests itself in the house temperature, and of course vice-versa when OAT is rising.  The importance of this is house dependent.  With a very lossy house or a house with low thermal mass it doesn't matter much.  With a very well insulated house, particularly one with UFH in a slab, or a high thermal mass for some other reason, it can matter a lot!

Posted by: @jamespa

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Does the system force you to use it this way, or is it just that Octopus wont provide any help if you attempt to use it in pure WC mode by increasing the 'set' temperature to well above desired?

Well, you know that it is possible to at least attempt to run it purely on WC but that isn't the way Octopus will commission it or, my impression, expect it to be running if you require support.  That doesn't mean that I know anything about what they will/won't support.  Certainly you don't get the degree of flexibility in the Octopus App that you may need to do so, compared to, say, the Vaillant controls.  If I understand what the Design engineer was saying this morning, the Cosy will modulate the flow, compressor and temperature as it nears/is at the set temp.  However, I didn't see any particular inefficiencies by running it as pure WC, compared to running it thermostatically - my big problem was the ability to reduce Flow Temp as needed.  All I can do is report my experience so far, which hasn't been perfect.  I have explained to them the different ways I've tried to run it to combat the issue I have and there was no gripes, but as I reported elsewhere, they've reset it back to the default commissioning state.

I will run it this way for a while to see how it fares: I'm expecting that the area with the thermostat hovers around the set temp and other rooms either gradually warm up until limited by their thermostat or gradually cool down because the heating demand isn't on for long enough.  I don't know if that experience was purely down to the fact the settings in the control module weren't the best.

Posted by: @andrewj

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However, if your driver is uber-efficiency then you really need to be with a non-Octopus install:

WC is not just about uber-efficiency....

Yes, fair enough, I most certainly don't have the level of experience you have James so I look at it more simply, and it's basically how Octopus position it - not as efficient, but more cost effective.  I haven't seen anything that backs that up per se by the way.  On a personal level I believe that running under pure WC control is the better way of doing it but it still stands: it isn't how Octopus will commission it to work and the App isn't particularly flexible.

We used Puraflow, I was very impressed with their design and heat loss.  We had a 3 hour visit and Heat Loss per room calculation.  He took into account window, size, glazing type, compass direct of wall, internal, external facing, Cladding and Loft insulation and doors etc.  They also work out heat loss variant as per if a room is a living or sleeping room with reduced temperatuire requirement for sleeping room. Below is an extract - hard to read, but is shows the existing heat loss and type of rad and then what is required and the news heat output.

I did a review of PuraFlow and gave them 10/10 for Pre Sales and 9/10 for Instal and 1/10 for Post Sales as this so far has been pretty much non existent. I have tuned my system with the help of this forum

Regarding the approach. I would say they offer a great documented design, but let them selves down by still following the install with defaults and tell you not to touch approach.  As far as price they originally say at the upper end, bit with some serious negotiating I got a 3K reduction. (Was a cheaper model ASHP), however I also think I caught them with some spare slots and a big team of installers who needed to be kept busy.  I also was quoted a reasonable sized water tank suited to the three people living in the house and not an army!.  

My biggest gripe with every single quote (I received 5) was the complete lack of transparency, without exception all I would get is the final price I need to pay less grant, each of the lines would either just say included or not have a cost. My assumption is at least some of the 7.5K goes towards installer margin and not the consumer benefit. For anything else in life I would expect a quote with parts, labour, design etc all separated. My install with 8 new rads, ASHP and Tank only took 2 full days.  

Room Type / Name Level Heat Loss (Watts) Current Emitter Proposed Emitter Qty Rad Output(s) at Design Conditions Notes

Living Room 1 Ground floor 776.39 600x1800 K2 Existing x 1 947.87

Living Room Main Ground floor 531.66 600x1800 K2 700 x 1800 K2 x 1 1073.12

Dining Room Ground floor 918.68 600x1400 K2 700 x 1600 K2 x 1 953.95

Kitchen Single storey 781.90 N/a N/A N/A Heat loss covered by open plan rooms -30 watts as nowhere to

run pipework for Plinth Heater.

Entrance Hall Ground floor 327.53 600x1100 K1 Existing x 1437.67

WC Ground floor 160.27 600x400 K1 600 x 0400 P+ x 1 218.43

Lounge Ground floor 1190.17 600x1200 K1 600 x 1200 K2 x 1631.71

Lounge Ground floor 0.00 600x1100 K1 600 x 1100 K2 x 1 579.12

Bedroom 1 (Ext) Upper floor 643.06 600x1600 P+ Existing x 1 873.71

Bedroom 1 Main Upper floor 353.13 600x900 P+ Existing x 1 491.67

Ensuite 1 Upper floor 142.25 600x500 K1 600 x 500 K1 New x 1 198.94

Bathroom Upper floor 287.79 600x600 K1 600 x 0600 K2 x 1 315.86

Office Upper floor 463.28 600x1100 K1 600 x 1100 K2 x 1 579.12

Bedroom 2 Upper floor 551.02 600x1400 K1 Existing x 1 557.03

Bedroom 3 Upper floor 291.30 600x1100 K1 Existing x 1 437.67

Posted by: @andrewj

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Well, you know that it is possible to at least attempt to run it purely on WC but that isn't the way Octopus will commission it or, my impression, expect it to be running if you require support.

I get the impression that that comment "they don't commission it to run purely on WC" applies to a high proportion, maybe the majority, of installers, whatever the heat pump.  In defence, getting heating to run on pure & correctly adjusted WC (as opposed to roughly set WC plus a thermostat) takes elapsed time, which of course we aren't prepared to pay for.

Unfortunately the heating industry lost its way in the UK a couple of decades ago.  Whilst some other countries made WC compulsory for boilers, we didn't.  As a result many installers and most householders find it an alien concept.  Its a shame really because, as a more or less direct result, we have been consuming (and paying for) about 10% more gas than we needed to because most condensing boilers are set up not to condense, as well as enjoying a lower standard of comfort, and are now on the back foot when it comes to heat pumps.  

Posted by: @andrewj

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It's basically how Octopus position it - not as efficient, but more cost effective.

Unless they have somehow degraded performance in the way their control systems work, or their heat pumps respond to different laws of physics, this isn't true!  In fairness if the WC is reasonably well adjusted, say to within a couple of degrees, then the penalty for bouncing off a thermostat is only a few percent.

I wouldn't get over concerned, as long as you are happy with the outcome (and things seem to be moving in the right direction) that's the main objective.  Finessing the operation, if and only if you wish, can come later!

Many thanks for all the content around heat pumps. it's been great learning all about this.

Hoping if I can get some advice, looking to have a heat pump installed but finding it hard to pin point the right system/ installer

Heads up, lots of info coming..... 🙂

Background info: 4 bed semi in Greater London Heat loss ~ 5.2KW(Heat geek) - 6.2KW(Octopus) with some minor improvements I'm currently doing with insulation
Most of my radiators while working look rather tatty, some rads are single fin and makes sense to replace them 

• DOT of -2
• My boiler is on the wrong location, about 20 years old and making lots of funny noises 🙂
• I already have mains water in my loft, electrics, is fully boarded and easily accessible.

General work required:

• Remove boiler from spare room on 1st floor
• Remove old hot water tank from 1st floor landing
• Remove cold water talk from loft
• Install new hot water tank in loft
• Install heat pump All pipe work / electrical work

I've had the following people round who have all done surveys, heat loss etc and come back with designs/ prices.(all prices after BUS grant)

Octopus eco 50* design temp

• 360% heating/ 300%hot water
• Replace 7 rads
• 200l tank
• Cosy 9 Costs
• just under 4k

British Gas 50* design temp

• Don’t recall scops but likely close to 400%
• Replace 7 rads
• 200l Valiant standard tank
• 5kw Valiant HP
• Costs 9k

Heat geek 40* design temp

• 400% efficiency heating & hot water
• Replace no rads
• 200l Valiant pure tank 7kw HP (might be able to do a 5kw)
• Costs £7.5k

I've also had a few online fixed quotes and estimates come through from the likes of BOXT, Eon & local installer ranging from £6 - £8k for Valiant Heat pumps/ water tanks 

I might get in contact with other like Aira or I might wait until the new Valiant HP reaches the UK.

All 3 firms, Octopus, British Gas, and HG have all said install the heat pump in my front garden with pipework going directly into the loft for the hot water tank, then use the existing pipework from my current hot water tank and extend that up into my loft extension.

Should be about 7m from HP to Hot water tank and about 5m or so to extend hot current hot water tank to new location.

Now here’s the issue Octopus cosy 9 fails the MCS noise test at the front of my property (I did try for planning permission which got denied) which means if I go ahead with Octopus we would have to install it at the back garden which is less desirable for me but I guess I could live with it if it's even possible. I have Octopus coming back for a re-survey of the heat pump location.

I can confirm the Valiant 5 & 7 KW HP's don't fail the noise test and are within permitted development.

So to hedge my bets I thought that's see Heat geeks, hence the survey and quote I’m concerned that Heat geek say no rad changes needed, I’m unsure with the proposal as the online estimate stated I could get the following for 8k but only came in £500 cheaper in the end.

Here's the original estimate from Heat Geek:

• 10kw AroTherm heat pump
• 200l valiant pure tank
• up to 10 rad changes
• 400% efficiency
• Cost - All the options maxed out Estimated £8000, (the estimator tool actually went down recently to £7650)

I know the online estimate is an estimate, according to everybody I’ve had round to survey including heat geek my house is a straight forward install - as heat pump retrofits go anyway.

I don’t see how the online estimate was 8k and the proposal for a 7kw HP & no rad changes is only £500 cheaper I’ve emailed Heat Geek who took 1 week and a chaser email to get a response that I'm not overly happy with:

It looks like a lot of the cost of your upgrade comes from the locations of both the heat pump and the cylinder. These locations mean a large increase in pipes and labour required to connect the unit to your home's pre-existing heating system, which means added cost. This won't have been captured in the estimate, as the estimate tool won't know where the heat pump and cylinder will go.

I've responded asking for further clarification and a detailed break down of the costs as I don't think the pricing model is correct.

Thanks so much to those who have read this and will help, I wish everybody in this process the best of luck, it's very hard but I hope it will be worth it.

Please feel free to ask any questions.

@editor thoughts? 

Welcome to the forums @jwhite and thanks for taking the time to write all of this up and it captures exactly why so many homeowners feel stuck right now. You’re not missing something obvious here, and your confusion is entirely reasonable.

A few things jump out straight away. First, your heat loss numbers are actually reasonably well aligned. A spread of roughly 5.2-6.2kW between Heat Geek and Octopus is a workable range, especially before insulation upgrades are fully accounted for. You’re clearly in the 5-6kW ballpark.

Where things start to diverge is not the heat loss, but the design philosophy. Octopus and British Gas are both designing to 50C at design conditions, which explains why they’re comfortable replacing a known number of radiators and keeping system risk low. That approach trades efficiency for certainty and usually means higher running costs long-term than a ‘genuinely’ low-temperature system.

Heat Geek’s proposal is the opposite end of that spectrum. A 40C design temperature with no radiator upgrades can work on paper in some houses, but it is far more sensitive to assumptions. It relies on existing emitters actually delivering what the model says they will, real-world flow rates being achieved and the building behaving roughly as expected. That’s not “wrong”, but it is higher risk and it’s fair that you’re questioning it rather than just accepting the headline SCOP. I remain sceptical about this approach.

Your instinct around the pricing inconsistency is also sound. If an online estimate allowed for a larger unit and multiple radiator upgrades at around £8k, and the final proposal removes those upgrades but only drops the price by £500, it’s reasonable to ask where that money has gone. The explanation about pipe runs and labour may well be true (relocating both the heat pump and the cylinder does add real cost) but it should be transparent. You’re right to push for a clearer breakdown, not because you’re being difficult, but because this is exactly the point where homeowners lose confidence.

On the radiator question specifically, I’d be cautious about a “no upgrades needed” claim unless you’ve seen room-by-room emitter outputs at the proposed 40C flow temperature. If those numbers exist and stack up, great. If they don’t, or they’re vague, that’s where problems usually appear later as higher flow temps creep in quietly to compensate. Again, I’m a bit sceptical here.

Noise and siting is another area where you’re thinking about this correctly. If the Cosy unit fails MCS noise limits at the front and planning has already been refused, that’s a hard constraint. Rear installation may be possible, but it changes pipe runs, losses and cost, so you’re right to wait for a re-survey rather than guessing.

Stepping back a bit, the bigger picture here is that none of these quotes are obviously “wrong”. They’re just answers to slightly different questions. Octopus and BG are selling predictability and speed. Heat Geek is selling efficiency and theory-led design. The tension you’re feeling is the gap between those two worlds, and that’s exactly the gap I was trying to highlight in the Steve video.

If I were in your position, the next sensible step would be getting clarity. Either get one independent, room-by-room heat loss and emitter assessment that you own and can reuse, or insist that whichever installer you’re leaning towards shows you, in plain terms, how each room meets its heat loss at their proposed flow temperature. Once you have that, the fog tends to lift very quickly.

You’re doing the right things though by asking questions, not rushing and not being dazzled by headline efficiencies or low prices. This process is hard, and it shouldn’t be, but posts like yours are exactly what help others navigate it more safely. Keep us posted on what Heat Geek come back with, because the detail there will matter, and it will be useful for a lot of people reading this thread as well.

@jwhite 

You could ask British Gas to price match Octopus, they did for me.

They might quibble at the additional cost of the Vaillant unit, but may offer to match and add the additional cost of the Vaillant HP, so could bring the cost down a fair chunk?

@jwhite

The design temp of Heat Geeks doesn't stack up to me. How can it be at 40c with no radiator changes, especially when BG are requiring 7 at 50c (who are pretty good at heat loss calculations)?

Sorry JamesPa if I accidentally tagged you in..

Posted by: @bash

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The design temp of Heat Geeks doesn't stack up to me. How can it be at 40c with no radiator changes, especially when BG are requiring 7 at 50c (who are pretty good at heat loss calculations)?

HG are estimating a lower loss overallwhich might explain it if existing rads are only just undersized with BGs estimates.

That said more rad upgrades will usually ultimately equal lower FT so generally better

Posted by: @jwhite

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It looks like a lot of the cost of your upgrade comes from the locations of both the heat pump and the cylinder.

That could well be true.  If they reckon they are going to have to do long and awkward pipe runs then they are going to build in time and contingency to cover the uncertainty as to what they will find.  Rad upgrades, by contrast, are predictable and easy!