I don't understand why the manufacturers engage in this pointless deception re. the useable capacity; this is the kinda crap we expect and get from politicians, not hot water cylinder manufacturers.

Ripple is not a money maker, for a £1k investment im getting around £5 per month if that. I live in a conservation area so solar is not an option and this is the only way to support renewables. In my previous house i was earning around £100 per month on a £9k investment which was far better. Ripple is more about supporting renewables and proving they are the future, also for the hippy factor and less for the financial one.

There is a certain heat loss by the cylinder. I putted an extra thermal isolation around the cylinder to stretch the time to reload. And I prevented the warm water pipe from micro circulation. That is when hot water can go up in the pipe and leaves the cylinder, that cools down und streams back into the cylinder. In some installations you can have a constant stream of hot water in exchange to cold water within one pipe. The same happen to my heating pipes. Now they go straight down to the bottom end then again upwards to the heat pump controller. You can feel these temperature losses circulations by touching the pipes by hand. They should be cold when the heat pump didn't run for an hour.

Thanks for sharing our rechargeable batteries😊

The MCS guides are very misleading. The problem is that an MCS accredited installer HAS to follow them, even if they know it might not be the best option... I have the other end of the problem as MCS would insist that I get rid of my 2 year old hot water tank (which provides plenty of hot water at 45 degrees all year round) and doesn't take into account that I can heat most of it off an immersion heater from Solar PV. It's really put me off getting an ASHP under the MCS scheme, total waste of perfectly good equipment. That said if I did replace the tank it would be with a Mixergy one...

@dougle03 is right! Try take a look a "basen green" kit. Is a diy solution but comes "flat pack" almost like an Ikea of battery diy.. way cheaper and still looks profrssional

#Jackperry - he was my intial advisor too and was ridiculously repsonsive picking up queries on weekend (non work days for him).. Obviously an old video but octopus are much more competitive now than they were back in Jan.... I'm just waiting for them to install. your roof is a bit "crap" for solar but I think you are missing the point of the battery.. At least for me by baseline use is about 10kwh during the day (i.e. excluding EV / etc) ... the battery will be partly charged by sun and partly by cheaper tarrif.. I think through this arbitrage my battery pays back in a reasonable time (15p out 7p in) ... still waiting for my install date, but have always had a good experience with Octopus so Im confident it will be a good install... Also I suspect they are quite prudent with their calculations... they were about how many panels they could get in given the virtual survey.

Excellent analysis. While we on the other side of the pond have different supply and rate structures, most are similar, so your approach to this work is quite useful. However, one dimension to consider when looking at storage is energy security. Depending on the quality of your source and/or the perhaps seasonal or storm effects, storage can be cheap at any price. But then you have to consider storage capacity vs. demand to compare to possible long-term (as defined by the analyst) needs.

Great walkthrough, thanks. I think we probably have the opposite, a 250L cylinder in a large house but with now just 3 of us living here. I found that our hot water was being heated by both the heat pump and the immersion heater, the immersion wasn’t just being used for the anti-legionella cycle 😢 Turned immersion off so its heat pump only, turned tank temp down to 48, increased the hysteresis to the max possible (4 degrees), hot water just once a day overnight and I think I’ve got the optimum configuration now. Its usually 1-2kWh to heat the hot water a day which feels like a good result

Good overview - of course rules of thumb are invariably rules of dumb. Leaving aside the technical nuances - there is always the option of educating the family to use less hot water by adopting the ‘submariners shower’ technique. We all waste so much water and they do say you only truly appreciate the amount of water you are using if you have to carry it . Challenge the family to carry 25 litres of water a 100 yards.😉

What tariff are you using for this data? Your system has worked very well.

I've ordered my kit which is due for delivery in August, I'd be interested to know what if anything goes against the roof and house wall, I think you mention a starter trim at 3:20. I guess the flashing then comes from the house wall at sit at 90 degrees on top the shingle? I'm a bit concerns that rain could push underneath the single and onto the roof itself!

Even the most inefficient heat pump water heater is 50% better on your real efficiency, your wallet set the heat pump to supply your need of hot water and don't worry about efficiency just take the savings in $$ and enjoy a meal out.

Hi buddy - love the vid. Can you confirm what type of heating you use? Do you think installing underfloor heating would help?

I suppose the value of having a battery is decided by how clever the tariff is. If you can benefit from hourly/half-hourly pricing, delaying export to the evening, and restricting import to between 2-5AM, then a battery could pay off faster than if it was just used to prevent importing.

Stuck down with 3m tape. It’s the Ikon Motorsport ducktail spoiler. Complete waste of time and money

While I was watching your video (again), there was an 'Everything Electric Show' video below it. Their guest was Mat Ferrel. When I first looked at it, I thought you were their special guest. The likeness is very strong. Anyway, thanks for the video. I think I commented before that I'm just waiting for an installation date from Octopus., so all information is useful. You might be able to answer a different question for me. I've already had solar and a home battery for 18 months. My gas consumption for 2023 was (thanks to the solar and battery) 10200kwh. I've watched a video by physicist Michael de Podesta, in which he said that a rule of thumb way to decide what size heat pump you need, is to divide your annual gas usage by 2900. This would suggest that I need a 4kw pump (3.52, to be precise). Octopus are going to fit a 9kw pump. Do you think that's too big. I watched lots of Heat Geek videos and he says that having a pump that's too big really makes the efficiency suffer. What's your view?

I want to ask you a couple of questions as moving into an 80s house originally four bedroom one bath but now three bedrooms with an ensuite for the master. The layout is quite open downstairs and I know a lot of the heat goes up the stairs to the first floor, thinking of knocking top part of the kitchen wall, into the dining room area even more open plan House faces the sea with prevailing winds so I’m not going to put cavity wall insulation in i.e. damp walls but do 300 mil in the loft replace all the single rats with K2s or bigger you’ve got a 7 kW heat pump would there be an advantage of getting a 10 kwheat pump? so as not to run so hard in winter months thinking ahead as gonna be retired 10 years tops going to have 18 solar panels Plus battery back up possibly up to 20 kWh to really future proof for our retirement with low energy bills I entertain your thoughts on this particularly about the size of heat pump and it’s comparable costs as do not want to be cold when older in winter especially if you get a bad winter much appreciated Rather do it all at the beginning Thanks Mark

In fairness at at store temperature of 48c you are still relatively low, yes it would effect your COP but you definitely have head room to increase that further.

Thanks for the insight. We're also a family of 5 with 2 bathrooms. For the last few years, I had been measuring how much hot water we use per day, on average, with our combi boiler. It's about 250l at a 55C flow temperature (my wife and son love extremely hot showers). I wish I had known about the heat geek cylinder: I picked a 300l solar cylinder (the solar versions have 2 heating coils that I will combine into 1 larger coil). It would probably have been easier with a 300L Vaillant but hindsight is perfect. I should be plumbing my heat pump in shortly so your comments about control will be very useful. I also have already plumbed in a Waste Water Heat Recovery (WWHR) from Recop - the side benefit is that it reheats the cold water used in the thermostatic valves so perhaps I will not have to run the water at 55C. Given what you said, I'll be aiming for 1 reheat a day at 48C, or less. Currently I am using the internal 3kW immersion. This heats up the top third of the tank to a toasty 62C. This covers us for a shower and a bath and reheats within an hour.

Megaflo 250lt with system gas boiler. If our three shower rooms will be used at the same time, I just push the one hour boost button, before going in. The cylinder has never ran out of hot water. Last year I was thinking to remove the boiler and get a heat pump. The deal broke when all quotes included a new cylinder and I’m happy with our decision to stay as we are for now

Did your installer promise a certain cop? I just don't see what grounds you would have to ask for any money back. Your system works albeit not as efficiently as it could if say it was done by another more competent installer. But unless you were guaranteed certain efficiency all installer is obliged to do is put in a working system which they did manage to do.

So basically, tank sizes are a con. Also, how this is going to work on a society wide scale to replace combi boilers - God knows. Most terrace houses for example that have lofts converted are not going to have anywhere for a 200L tank.

My hot water COP is also relatively low on the Vaillant with Unitower Plus, but it's OK. In the warmer months the actual energy consumption for hot water is around 0.8-1.5kWh per day and about 2kWh for the Legionella cycle. I don't see much of an improvement in hot water performance between 15°C and 30°C ambient temperature, but as long as the actual energy consumption isn't too high I don't care much about COP. Heating is also OK. The COP isn't great since my house is well insulated and the heating only needs to run when it's actually cols outside, but the actual energy consumption and cost have been pretty low, so I am not complaining.

Great video and breakdown, thanks! It all depends on your use case scenario and where you see your energy usage heading (eg are you planning on getting an EV in future etc)? The main reason for getting a battery will be energy security (eliminate reliance from the grid completely) and the ability to export your unused solar back to the grid at peak times. Battery and Solar are not binary propositions (ie not one or the other) I would say design and build your system in a way that takes advantage of the solar now, with the ability to scale and include a battery later. I'm currently researching into how to add a used EV battery to a solar set up (90kwh secondhand for £2000) there's tons of videos out there if folks repurposing used EV batteries into their solar set ups. That's if you really wanna go green!! Cheers

Hi great post love the content. I also have a sunsynk system 2x5kw inverters in parallel. Im struggling to understand your roof degrees. If North is 0 degrees and clockwise increases towards south is 180 degrees. What angle is your north west roof ? I have a small roof facing about 320 degrees past North and don’t know if it’s worth adding any panels.

I just want to ask you about something I picked up on at 4:20. You said you had microbore pipework with your heat pump. We also have 10mm microbore pipework in our home (3 bed detached) and that is the number 1 barrier for us re heat pump adoption. You you tell me a bit more about your own system and any adaptations made to work with microbore?

As a short term fix you could increase the store temperature. Our 3-bed, 160 sq m property had an oil boiler which was replaced 11 months ago by a 7kW aroTHERM Plus system with a 250L uniSTORE cylinder. There are normally two adults living at the property and we find that an overnight cycle to 52 degrees provides all our hot water needs for the day. According to the myVaillant app, our hot water electricity consumption so far for 2024 is 458 units at 9p/unit (8.5p since 1 July) and the COP is 4.2. When my son and his family came to stay, I simply switched to manual for the duration to ensure there was hot water at all times.

Seeing this video I think you are being much too kind. This cylinder does not work for your family/home and the documentation does not leave much room for debate. Have them swap it out, pay for the price difference between the current cylinder and the required one. Maybe add some money for the time used or offer to pay list price for the new cylinder and sell the current one yourself. If it was my home I would be furious. Enough hot water is a basic requirement for any home, not a bonus feature.

Hot water generally is the biggest issue with heat pumps from an installers pov. Generally we try to put forward a larger cylinder so for yourselves I would of spec'd the 300 not the 250. This is because we have found that when people go from a fast cycle time from a conventional fuel source to a heat pump larger families have issues managing their water usage. It's normally better to increase the volume to keep the efficiency and have people not run out but we have to take into account space, cost and energy/water wastage. With a conventional heat source it's very easy to have a small cylinder with a faster cycle time because the temperatures are higher, around 17-25 minutes in some cases but you can quite easily double that once your heat source is a heat pump. I will say that if anyone has daughters (especially teenage ones) it's a better idea to size up, if you have boys it's less of an issue.

How hot is your water compared to a gas boiler?

Mcs is just for guidance . occupancy and age(teenagers multiply usage by 3) dictate hot water consumption within a household

I’ve never found out what the temperature of the 45 litres/person guidance is. It could be 45 litres of mixed bathing-temperature water (e.g. 38-40C). Or it could be 45 litres of the stored water in the tank. If it’s water in the tank, then what temperature is the guidance talking about? It could be 48C, but more likely to be 60C. Either of those would create more than 45 litres when blended with cold to a usable temperature. Does anyone know which the guidance is taking about?

That's really useful, I hadn't considered that 300lt might be an advertised size rather than volumetric, though I'd guessed the coils would take up some space. A quick back of the envelope suggests that my partner can use 135lt of 40 degree water in a single shower. Add in the two teenagers and we're going to need a bigger tank... 275lt useable minimum.

Remember the first eco thing to do is reduce. (fair play though I see in the video you've tried this). Before I got my SunAmp (no room for a big tank) I spent £300(!!!) on an Hansgrohe aerated, "ecosmart" low water shower head. (40% less water when showering). All other hot water use in my house is minimal. Yet to run out of water. MyVailant says my Heat Pump efficiency with 70C flow is 4.5 (summer 2024).

What country are you from?

Thanks very much for sharing - great content, and all in one take!

I have a Mira shower which measures water usage. My daughter uses 180 ltrs 🤦🏻‍♂️ My heat pump reheats, as I have a battery it’s not a big deal.

I set my Vaillant 250L HP to heat with a heavy bias to hysteresis, leaving it to do its own thing and only use the time control to prevent re-heating at the really undesirable times. Opening-up the times for heating the DHW can help and whilst I appreciate that exporting solar brings in revenue the value you get by using that for HP use at [value] kW x SCOP does soften the blow. Of course, it is amazing how quick the kids grow-up and disappear from the calculations. It's a bit of a shock when my daughter comes back for a visit though - I have settings worked out just for her!

The heatgeek cylinder (works in reverse, cylinder stores hot water as a battery and then DHW picks up heat from it via a coil of piping running through it) seems to be the solution for many showers a day whilst taking up a tiny footprint. Well worth looking at even if you don't plan on changing anything, just for content for your channel.

Thanks for the video, sorry to hear you run out of hot water from time to time. It is very good of you to share your concerns with us all. If I may make one small point though on your interpretation of the data from the MCS site about required cylinder size for beds/baths. From memory you have a 7kW Aerotherm ASHP. By going straight to the 3-6kW hot water command column on the MCS table you are perhaps assuming that you are only getting 7kW of water heating with the ASHP running at max. Of course, this is incorrect as the ASHP output is dependant on various factors, but is rarely just the rated output. The Aerotherm 7KW ASHP has an output of over 8.6kW at 40 degree flow temp, according to the Heatpunk website analysing my system. This might not be absolutely precise, but the general gist is you will get a lot more than 7kW for most of the year, especially when the cylinder is cold and flow temperatures are lower. For this reason, I believe you should probably split the columns of the MCS chart for analysis of your system. It still says you don't have a big enough cylinder, but it does reduce the discrepancy. Having gone through your stage of parenting, I would say that your boys will be teenagers in a few years, so their water consumption for washing will then plummet, removing your consumption issue! Small mercies of grubby teenagers.

You should have got a joule cyclone tall and slim

Achieving the perfect size of hot water storage cylinder is probably even more complicated than you have described. When I swapped my 160L tank for a 200L version with better insulation I failed to anticipate one of the negative consequences. My wife uses our airing cupboard to store bed linen and towels but the shelving is now about 350mm higher up so she has difficulty reaching the top shelf without standing on something. I am reminded of this inconvenience on a regular basis.

You might want to try a water waste heat recovery system in both your bathrooms. Some of them are silly prices new but there are sometimes bargains on ebay. Even new it would probably be cheaper than a new tank to install and will save you more in energy costs I think.

Strange that the Vaillant cylinder is by the volumetric capacity rather than the DHW capacity. This is in marked contrast to the heat pump power output rating which is on a worst case heat output. Good luck with chasing up British Gas.

I have a 290l Joule cylinder for a similar size house. I operate it on hysteresis, not on schedule and with a target temperature of 43 degC. It usually does 2 cycles per day and takes 30 minutes to recharge. It is debatable to claim installer negligence because he will argue that you can run your DHW at higher temperature. Depends on what scop was sold on the contract, but even tho, these are indicative, not contractual values.

After watching this I did a little Bit of digging myself, my Cylinder is 200l but there's only 3 of us at home. Would have got away with a 160l tank which is the smallest Samsung tank. I'm not about to pull it out and replace it though. lol

Goes to show the complexities of new home heating technologies. Whereas a gas boiler could easily accommodate everyone’s needs, the design & usage of a modern system is more critical even to get cost parity let alone save money. Great to see people innovating and trying out different solutions.

Octopus use 50L per bedroom +50 to calculate tank size Which works out to 250L. There is only 2 of us so we only heat tank on Wed/Fri to 47° and Sun to 55°.

Thanks for another great Video, it's great when people are happy to share missteps as well as successes. I had two thoughts out of this firstly there is also the issue of oversizing, for example in my case I am a single occupant in a 4 bed house so my own needs would be catered for with a 100 ltr cylinder and this would be most efficient from a draining the tank daily (ish) perspective. However in planning the system I need to consider if I ever sell my property it is much more likely a family of 4 would buy it and hence there requirement would be a 250ltr Cylinder so I would need to drastically oversize for that probability. I think there is a easy/neat solution to this. Market a cylinder type that has two chambers insider of say 2/3 and 1/3 capacity and have a physical lever mechanism on the outside of the tank that allows a flap to slide open in the division to allow use of the smaller top chamber when needed.