Cosy 6 Heat Pump Test Results are poor. Does Octopus have a trump card?

The Cosy 6 has been tested by MCS and here are the figures.
They're not looking impressive on a spec sheet. Hopefully it will do better in the real world!
Can Octopus play their trump card of native smart tariff integration?
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My system :
Vaillant Arotherm Plus 7kW
200L UniStor Cylinder
45L Buffer tank
140sqM Detached 1997 built house
10mm copper microbore pipework downstairs
Installed by British Gas in November 2023
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[@Lewis_Standing]

Octopus's narrative is that its easier to role out high temperature heat pumps with less palava, and make the economics work with smart tarrifs. A rebalancing of tarrifs from charges on electricity to gas would help too. Low temperature systems are of course better. But there is still barriers to mass rollout that exist, and high temperature systems would ameliorate these. Id personally want a low temperature system, but my current house would require a replumb to make that work.

[@UpsideDownFork]

With my microbore pipework I had presumed my house would require a re-pipe. Then I saw the heatgeek rule of thumb tables and caught a glimmer of hope. Went on to use heatpunk to assess my own heat loss and confirmed for myself that microbore was more than sufficient and radiator upgrades were a lot easier than I expected.

[@YewDuct]

@@UpsideDownFork Wow! You mean there's hope for my 1999 built home with 10mm outer diameter PVC pipe? To be honest, with the gas boiler, even in winter, my radiators are usually cold to touch and having them at 30C would make them warmer than I currently experience them.

[@UpsideDownFork]

@@YewDuct 1997 built house here. Luckily my microbore is all copper so has a larger inner diameter than plastic. You will have to work out the heat loss per room and then you will be able to calculate if the microbore feed per room is sufficient to carry the amount of energy you need. Many of the houses with 10mm microbore just have a small end section of that size and sometimes connect into 15mm pipework just inside the wall or under the floor.

[@M0j0]

I guess the high temp efficiency ratios can only go so far with current gen heap pumps? Relieved in a sense, as we've just had a Daikin Altherma 3 installed in March and were thinking should we have waited for the cozy!😊

[@71brp84]

Spotted the MCS certificate when it was published at the end of May. Worse than the Daikins they're currently installing.😂 They'll have to do something pretty special with a tariff, me thinks.

[@dama054]

Your right to point this out thanks

[@mentality-monster]

If octopus can sweeten the deal with a tariff for the Cosy 6 it could still be a winner. Every heat pump installed is tons of CO2 not being burnt in a gas boiler. But agreed, was hoping for better.

[@UpsideDownFork]

I agree, Every heat pump is a good heat pump!

[@Biggest-hz7ng]

​@@UpsideDownForkEvery well-installed heat pump is a good heat pump perhaps?😉

[@edc1569]

So let me unpick this, the government gives octopus 7.5k to install a sub par heat pump that then creates a decade of locked in additional income for octopus. Clever I guess.

[@geoffreycoan]

Useful pointer to the MCS database, thank you. I’ve looked up the details for my (now 2 year old) LG Therma V; its actually has better SCOP at 35 degrees than the new Cosy heat pump! Your Valent is overall better SCOP than mine, but not by much, but you’d expect that newer pumps would be better. It does rather destroy the assertion that was being made that the Cosy HP was a high temperature heat pump, suitable for any house install. Yes, but at what SCOP?

[@UpsideDownFork]

Sometimes i'm surprised by how different the various pumps are because the fundamental technology is well established and mature. It seems as though the physical engineering hasn't improved in several years but the control strategy and algorithms do seem to be considerably better on some of the newer models.

[@colingoode3702]

After all the hype these are not good stats from what is a brand new R290 Heat Pump (albeit a re-designed RED unit). I can't help thinking that the Cosy 6 was designed & optimised for use in higher leaving water temperature systems to avoid pipe & rad changes which, makes the system cheaper to install, if not to run. The angled top discharge fan also makes it more flexible when installing it close to a fence or similar boundary obstruction which may prevent the use of a traditional side discharge fan unit due to air recirculation issues.

[@joshuab9858]

i've just been offered the cosy 6 rather then dikaina to get installed quicker - should I go with the cosy 6 or wait? - I can get one as my house only has a 3kw heat loss

[@brackcycle9056]

The MCS SCOP is only half the spec . When phoned MCSCertified couldn't give the test conditions, but said they can supply the names of certification companies ( different companies for different models) so a researcher could investigate,.. ( MCS quote SCOP at, say, 40c , but people don't run a fixed flow temp for a season, so confusing). . We may find Cosy 6 has been optimised for other factors other than this SCOP test . .. .. Perhaps it is better at defrost cycles? perhaps this makes up for lack of test SCOP? Perhaps it is quiet , if Sound Power Level is lower it still could be a winner. Perhaps it has been built for reliability? . Perhaps it is just cheap ? "Free install" was Greg's suggestion at the cosy launch last year a good price point . If its a free install that cost £300 a year extra to run that might be better than a £4000 install. ( & octopus service is £100 cheaper than others).

[@UpsideDownFork]

Lots of relevant questions that have also crossed my mind! Interestingly, if you dig into MCS you will find this document mcscertified.com/wp-content/uploads/2021/10/MCS-007.pdf It references BS EN 14825:2016 as the test, but if you go and check that out, it was withdrawn in 2018. MCS is a bit of a joke really.

[@jamesg9592]

Can you share any links for people that have hacked their heatpumps to get the most out of agile? Would be interested.

[@UpsideDownFork]

This is the place to go: community.openenergymonitor.org/

[@MikeGleesonazelectrics]

CoP and efficiency isn't necessarily the be all and end all. Reliability and longevity would be pretty high on my list. I have heard from one heat pump installer that the vaillant design does have some design flaws, albeit good cop figures, so we shall wait and see!

[@anyuone]

Thanks for another great video, really interesting. I wonder what Octopus will do with those figures. Do you have any knowledge or experience of Tepeo? Especially the upcoming Combi boiler.

[@UpsideDownFork]

I did research Tepeo. I'm not a fan.

[@_Dougaldog]

@@UpsideDownFork "I'm not a fan" No pun intended ;-) ?

[@anyuone]

@@UpsideDownFork Any particular reason?

[@UpsideDownFork]

@@anyuone 1. Upfront cost for most people will be higher due to the BUS grant. 2. It will always consume 3-4 times more energy than a heat pump. 3. The 40kWh stored energy is not enough to see some modest sized homes through the coldest winter days, so will need to be recharged during day time hours which ruins the business model of only charging off peak. Conduct your own heat loss survey to check whether 40kWh will see you through a whole day. On our absolute worst winter days we almost used 40kWh of electricity through our heat pump to generate over 100kWh of energy for space heating and hot water. I recognise that this is only a handful of days, the exception rather than the rule. For full context we live in a modest 140sqM 4 bed detached home. Hope that helps.

[@MikeGleesonazelectrics]

Maybe octopus are aiming for a wider market sector with a higher flow temp? Depends what their objectives were..

[@davideyres955]

This is one of the things that concerns me about heat pumps. Everyone focuses on the scop and how it’s 400% efficient, etc. it’s more complex than that with a boiler there is a house heat up time which is based on how long the unit has been off and how long it will take to get up to temperature. I am not in my house most of the day and use very little of the house and having a boiler with zoning has a specific cost where as to get the scop high I’ll have to heat the entire house for most of the day. So if I’m burning electricity for an additional 4 hours to get to the same temperature as the boiler can do it in 1 the. No matter what the scop is I’m going to be brining more electricity. There are so many nuances in the usage that it’s not all about being above a scop of 3.5 being better than gas. If you then look at the additional efficiencies they add like lagging internal pipes and running lower temperature hot water cycles then it’s more complex than it first appears.

[@UpsideDownFork]

Good points raised. We used to run our boiler every day 6am-7:30am and 4pm-9pm. We then went to a heat pump running 24/7 and saved a load of money by doing so. Different lifestyles may benefit more from the advantages of A2A such as quick warm up time and localised zoning. There are some good theory videos covering these principles on the heat geek channel. Thanks for commenting.

[@DaliPickle]

@@davideyres955 Excellent comments, SCOP is over hyped re savings, etc., as you say so many variables down stream from when COP is measured. Just finished our first full year and, albeit a mild winter, we didn't feel cold, lack HW or buy loads of electricity. Our main goal for going HP is environmental. And before responses about the carbon cost of HP, replaced boiler, new radiators, etc. we are thinking long term, probably beyond our lives (leaving the property in a better place). Monetary considerations are secondary and I realise I am fortunate to be able to say this.

[@DaliPickle]

Arrived a bit late to your forum and just catching up on your many interesting posts. One question I have, How did you calculate your HP and HW monthly COP?

[@UpsideDownFork]

Thanks for your question. COP is calculated by taking the heat energy output and dividing it by the electrical power input. For most heat pumps this information is easily accessible and the integrated measuring equipment is fairly accurate. Some heat pumps do not show this information. Some owners prefer to fit 3rd party monitoring equipment to check the system efficiency.

[@DaliPickle]

@@UpsideDownFork Hi, yes I understand that. But how did you measure the heat/energy output. Clearly energy input is the electricity used.

[@UpsideDownFork]

@@DaliPickle my heat pump has an in built heat meter which provides the reading. If you're not aware of what they do, it measures the flow and temperature of the water in and out of the heat pump and can work out how much heat energy has been delivered.

[@DaliPickle]

@@UpsideDownFork Thank you for the reply. Unfortunately I don't have a heat meter fitted. Enjoying your insights. How do your measured monthly COPs relate to what your installers quoted for SCOP?

[@UpsideDownFork]

@@DaliPickle so far we are above the COP for heating by a bit and far above the COP for DHW. Which heat pump do you have?

[@davidwatson4738]

You say stay away from octopus cosy - any reason for that if you have a battery and can charge it up twice a day. What tariff would you recommend?

[@geoffreycoan]

Personally I’d recommend either Octopus Agile or Octopus Tracker to run a heat pump as these have an average lower price than Cosy. Cosy works IF you have sufficient battery storage to run the house and the heat pump off in the day-time and peak rate periods, AND you have sufficient inverter throughput to charge the battery in the cheap rate. Otherwise if you are running the heat pump in the day/peak periods, its more expensive

[@davidwatson4738]

That’s ok for summer but don’t see it working in winter. I have solar and a Tesla 13.5kwh battery so pretty much zero electricity from the grid and on the 15p guaranteed export. What about when the solar goes down in September what would then be wrong with cosy as I can fill the battery twice at 11p/kwh (and will be able to fill the battery from zero) while also using power in the house at 11p/kwh.

[@geoffreycoan]

@@davidwatson4738 As I said, it all depends on your battery storage, inverter capacity and heat pump demand. I have solar, battery and a heat pump. In the winter my heat pump draws 3-4kW when it’s running and a typical winter’s day is about 25kWh for the heat pump (plus about 14kWh for the house). My battery capacity (13.5kWh) and inverter throughput (5kWh) isn’t sufficient to run the house and heat pump off the battery in the Cosy off peak periods so I would end up drawing from the grid. For me, Agile was the answer, an overall cheaper rate but you do need battery automation to manage the battery charge and discharge. Tracker is a simpler tariff that doesn’t require the automation (or batteries)

[@davidwatson4738]

Thanks I will look into that - just had everything installed a couple of months so will have to figure out what’s best for winter.

[@UpsideDownFork]

Geoffrey has it all covered I think. Situations do vary. If you have the battery capacity to bridge the gap then Cosy may work for you. My statement was quite a broad generalisation. if you don't have battery, Agile or Tracker will always win over Cosy. If you have an EV then IOG is probably your best bet but once again dependent on your home storage battery capacity.

[@lumbarsupport]

While accepting that good design is paramount, it is worth noting that, generally, the MCS tests show that R32 heat pumps have significantly better SCOPs than their R290 equivalents, because R32 is a more efficient coolant. You can see this most clearly by comparing like for like R32 vs R290 models, for example the Misubishi R32 6kW model (PUZ-WM60VAA) has SCOP of 4.81 at 35degC, compared to the Mitsubishi R290 6kW model (PUZ-WZ60VAA - a much newer model) which has a SCOP of 4.39 at 35degC

[@Sean_S1000]

Sounds like no one's prayers have been answered, no miracle heat pump that can do 60-70 degrees at high efficiency 😅

[@Etacovda63]

you literally can't get massively high efficiencies at those temperatures, physics is physics

[@dominicgoodwin1147]

Some of those low temperature units may have a higher scop but if you actually want to run them up near the 55C mark, then you will be stressing the heat pump and it’s going to break down sooner. Also if you absolutely can’t ever push the temperature up to 60 for a legionella cycle then you’ll need an immersion heater too which adds complexity and will obviously be less efficient for those cycles.

[@UpsideDownFork]

All of those units I selected are R290 units which have been branded as high temp. They can all complete a legionella cycle without an immersion heater.

[@dominicgoodwin1147]

@@UpsideDownFork then why do the test results all show 0 above 55C? If they are being sold as high temperature units then we’re going to want to know how they perform at 60, 65 and 70.

[@UpsideDownFork]

@@dominicgoodwin1147 I agree with you, they should show that. I've covered the questionable marketing practises surrounding the so called "high temperature" heat pumps before.

[@BritishAnts]

Dont be afraid to take on the fan boys! Octo appears good but when peoples videos follow a link where they get a golden handshake you got ask yourself is their video genuine or the grifting for the greasy £50 coin! Doesn’t hurt to call these companies out and keep them on their toes! ❤

[@geoffreycoan]

r/e Turning on and off the heat pump at specific times to take advantage of Smart tariffs - don’t do it ! Have a look at the heat geek video on smart tariffs (eg Octopus Cosy, Agile, Economy 7), they crunch the numbers and prove that trying to optimise the heat pump for when the electricity is cheaper is a false economy as the heat pump has to work much much harder and at a higher flow temperature to keep the house sufficiently warm. We are on Octopus Agile and run the heat pump all the time in the winter (with overnight setback). When on the few days it was super-expensive 60p/kWh in early December 2023 and in the DFS savings sessions we turned our heat pump off for the hour or so, but otherwise we just let it run low and slow to keep the house warm. The battery took out the worst of the Agile peak periods, running the heat pump on previously stored cheaper rate electricity

[@UpsideDownFork]

Turning on and off is definitely ill advised. I would advocate for setback during the 4-7pm agile period if you don't have sufficient battery capacity to cover you. Or just stick with Octopus Tracker which is a smart tariff that works really well with a heat pump and no battery storage required.

[@Biggest-hz7ng]

@@UpsideDownFork the heat pump monitor site lists numerous high performing installations. Many of them don't run the heat pump between 4 and 7pm because of Agile. Look at a typical high use winter's day and you'll see many don't use energy at those times.

[@Etacovda63]

its highly dependent on your house, and the vast majority of people don't have a battery. Your advice is generic and not useful. Definitely much better to turn off and on in my situation, if i listened to you i'd be worse off.

[@UpsideDownFork]

@@Etacovda63 Not so dependant on the house, but more dependant on the lifestyle. Rule of thumb is that if you spend 12 hours or more per day in your home then you will be better off financially by running constantly. If you occupy your home for less than 12 hours per day then it can be debateable but definitely still worth doing some thorough calculations and modelling or testing both ways.

[@Etacovda63]

My heatpump says its certified and yet only has 35c and 45c flow temp SCOP ratings. Having a large amount of ratings per degree C with one heatpump, and having only two with another does not breed any confidence whatsoever.

[@UpsideDownFork]

Yes, you have a good point. Another flaw in MCS.

[@BassPunk]

Do you suffer from the Vaillant Arotherm Firmware 351.06.07 Problems? Maybe this Cosy 6 heatpump can improve its COP with firmware!

[@UpsideDownFork]

@@BassPunk mine has the later firmware 0351.09.02, so no issues there 👍

[@Roedy_Coedy]

After being excited to get a Cosy 6 this has really screwed my plans up. HOWEVER! After seeing HeatGeek's Mini hot water cylinder I'm now looking to go Air2Air instead. I recall seeing a A2A Heatpump that also runs a hot water cylinder so that is now back on the cards. I'll obviously prioritise Solar first though so no additional load on the grid in summer.

[@UpsideDownFork]

Any heat pump is a good heat pump!

[@edc1569]

I wouldn’t live too much on KZbin, plenty of good systems out there without KZbin fanfare.

[@Tim_Small]

You could take a look at the new Samsung R290 units.

[@carpcrazyboom5190]

Why woukd you put a substandard heatpump in because of a tariff? If you can put a valiant in just do it, i cant fault them for reliability and im upto 35 installed now, and ive fitted daiken, mitsubishi and samsung aswell

[@UpsideDownFork]

@@carpcrazyboom5190 Cost. Unfortunately most can't afford the Vaillant kit.

[@carpcrazyboom5190]

@UpsideDownFork sorry but it's tried and tested pretty well so reliability isn't an issue unless the install is sub standard and this investment in your property isn't one you really want to scrimp on, also their not that bad cost wise? Or is compared to ine of octopus quotes that need adjusting to get the best results out of an install 🤔

[@UpsideDownFork]

@@carpcrazyboom5190 If you watch any of my other videos you will see that I have Vaillant in my own home. Very happy with it 👍 But I have talked to hundreds of other home owners and the same response comes back every time. They want to do the right thing by ditching a gas boiler but they can't afford to pay a premium to do so. The Cosy 6 is based on the RED heat pump which has a good reputation amongst those who have actually worked on one. We'll see how Octopus installs pan out. They don't look to be the best but also far from the worst eco4 type installations that are rife. We have to achieve mass adoption. The only way to do this is by scaling up and big firms like Octopus are positioned well to do this.

[@bencampbell2041]

The previous certified devices are the R.E.D heat pumps that Octopus bought out. Similar efficiencies to the Cosy... The units you looked at arent by the same certification body, i dont have a lot of trust that certification bodies are that close in standardisation in general. Would be good to see the numbers on heatpumpmonitor before making any conclusions

[@UpsideDownFork]

Great point! There is definitely the potential for margin of error between testing bodies. The do all test to the same BS standard though. Heatpumpmonitor is an amazing snapshot and growing quickly as the months go on but the small sample is still not fully representative of how well pumps may perform in a wide variety of homes.

[@bazcurtis178]

I would like to hear from some Homely customers. I am on Agile. My inverter can handle Agile no problem. Heat pumps should do the same.

[@UpsideDownFork]

I haven't heard from any Homely end users personally but I have been in talks with Homely directly to bring some content about their product to my channel. Stay tuned.

[@carlarrowsmith]

Poor results for the Cosy 6 but the other big player Aira heat pump is seriously efficient. Seems to be 0.5 better than the Vaillant 5kW!

[@crm114.]

Valliant tend to underrate the performance of their products. The 5kW unit is capable of outputs far >5kW and I regularly observe COPs of >5

[@carlarrowsmith]

@@crm114. I'm referring to MCS test results rather than manufacture ones.

[@Etacovda63]

@@crm114. COPs without outside air temperature are worthless. These COPs will be at a particular temperature, and it sure as hell wont be 10 degrees

[@kavanobrien6547]

Much of the stuff you was talking about was completely lost with down load and with different ways the system is installed or set up , and looking at a few videos by different installers, the two that stand out for me at least are Urban Plumbers and Heat Geek , they look at houses and how the systems were installed and many have had things that make the system inefficient with extra circulating pumps or extra vessels or wrong this or that and make the system more complicated than it needs to be, so my point is it’s a pity there isn’t some kind of blue print or program that would give you the items needed be it one circulating pump instead of two , you don’t need a buffer contraption or with your house you would be better having this size heat pump because you live in Scotland or in Devon as I do you would waste money on that heat pump you only need this size and so on , sorry for my long messages never been good at explaining things in a short way , when you think you can put the sizes of the rooms in a program to see the heat loss element with a calculation = pity there isn’t similar for the design of the perfect or near perfect design for the actual system at least the owner could do some work on having a little knowledge so they would know when they saw an installer putting in an 11kw heat pump when you know you only need a 5kw one , or when you see 17 circulator pumps being unboxed rather than one or two there’s going to be a problem, so many house that these two gentlemen have visited that the installation is wrong or badly designed just wondering in the future is there likely some program that’s in the pipeline- whoop was there a little bit of humour? .

[@UpsideDownFork]

The industry does seem to be improving and evolving rather quickly!

[@kavanobrien6547]

@@UpsideDownFork for the benefit of whom ? If the two heat installers mentioned in my last message are looking in disbelief of how the heat pump and installation was devised how then do we as normal day to day people tell if we have just had a good or bad job done and instead of it being efficient it’s ends up costing more to run than a gas boiler due to lack of knowledge by the installers.

[@UpsideDownFork]

@@kavanobrien6547 Many of those systems that they look at are several years old which in residential heat pump market terms, is ancient history. I'm not saying that poor systems aren't installed any more, i'm just saying that training has improved and good principles have been more widely spread. The situation is improving all the time. Ultimately, the main beneficiary is always the householder.

[@kavanobrien6547]

@@UpsideDownFork Yes you do make some good points , I can’t help thinking of the quote from Samuel Langhorne Clemens you would probably know him as Mark Twain = History doesn’t always necessarily repeat itself but quite often rhymes. Maybe someone will come up with a concept in regards to what is needed equipment wise to give individual households to ultimate efficiency, they have so many programs in regards to room sizes for heat loss and the efficiency of the tariff the way you can alter the system on the different displays on the system = why has there not been the guess work been taken out of what is actually needed for a home , still sounds like if you get ten installers you would get ten different systems, that’s the bit that’s the problem.

[@edc1569]

Wow, that’s terrible - but I guess what were we expecting!

[@UpsideDownFork]

Not terrible, but not great either...

[@andyballard1883]

All of the efficiency discussion goes out the window for me when the Installation costs over and above the £7,500 grant can vary so much. I had a £2,500 price difference between quotes from British Gas and Octopus and even then it was all heavily caveated with 'may be additional costs identified on the Job' .

[@UpsideDownFork]

That is definitely frustrating! It's ultimately the reason I decided not to pursue the more expensive HeatGeek route as I would not even get close to returning the extra invested capital with them. Cheaper install with moderate SCOP is typically the best financial route.

[@pt6423]

This analysis is potentially flawed. The error is there is no information on the EPC rating of the property or the size and type. To compare two different properties makes video irrelevant.

[@TJames]

Why? The primary variable adapting a running heat pump to a home installation is flow temperature, which is set in to adapt to changing weather and the individual installation as the system runs. It can be modelled before installation in programs like Heat Punk... Knowing the efficiency at different temps then becomes a useful comparison.

[@UpsideDownFork]

The MCS database doesn't compare homes. It compares heat pumps under lab conditions. Besides that, EPC's are fairly irrelevant to heat pump operation. They are prone to human error and based on many assumptions rather than data and calculations.

[@GdaySport]

A cynical individual couldn't be blamed for thinking that an energy company is disincentivised from supplying energy efficient heating...

[@UpsideDownFork]

That's one way to look at it for sure.

[@edc1569]

Nice deal collecting a 7.5k grant to lock a customer into 10 years of energy from a supplier.

[@UpsideDownFork]

@@edc1569 customers are free to change energy supplier at any time. You also don't need to be an Octopus Energy customer to have one of their heat pump installations. There is no lock in for 1 year or 10 years.

[@Tim_Small]

I very much doubt that this is the case. This is an early product from a small and new company (Octopus bought the company which makes these a few years ago). It's just not as good as some of its competitors. Competitors who have much bigger R&D budgets and have decades of experience making heat pumps.

[@kenbone4535]

It's a gimmick

[@UpsideDownFork]

Time will tell for sure.