Wow, I’m super impressed with this - I admire the time and effort this must have taken you! What I’m really interested in doing when I get round to downloading my own copy is to take out the 3 hours of expensive heating on the Cosy tariff, and see how that changes the numbers. I think most people would simply avoid having the heating running for that peak time - if you’ve got a heat pump then the assumption would be that your house should be insulated well enough for the temperature not to drop significantly.
Thank you. Yes, you can do that by changing the number of peak heating hours in the green cell L16 to zero. That then doesn't use any heating during those three peak hours. It's fun to tinker with various settings to see what impact it has.
First of all, what a great spreadsheet, so involved. I want to look at the intelligent Octopus and do have a very high use of electricity. I have found with my Tesla Powerwall 13.5kWh and solar PV, summer is very cheap, but there is still a fair bit of use as it is not sunny all the time! As it reaches the winter, the bettery is filled overnight at cheap rate, around 3.3kWh per hour, so i find that I need a longer cheap rate, especially when adding in my EV charging. So, not to surprised at you result!
Yep, same here, Intelligent /Agile Octopus and high electric use. Problem is, Agile is 34p/kWh one minute and - 3.4p the next. Although I think it does work out that, the more wind there is, the cheaper it is, so can be factored in using the weather side of the graph too, maybe!
Tim, great work, taken a copy, a big TY for making it available. PV modelling would be the next logical progression for this, I seem to recall that the 20 year weather data had some form of Sun index in it?????? Apply a scaling factor to ones own installation, nudge nudge wink wink!! I know it's not where this started but... Also I know your limited on the number of panels you can fit but do they all have to fit on the roof?? Be great to play the whatif game with panels as you did with battery size 😁
Yup, that's absolutely the plan once I've got some solar generation data to compare to the solar energy index included in that data feed. It'd be good to have a complete system modelled, then this spreadsheet will be unstoppable.
Very helpful thanks! I’ve been meaning to do something similar myself but you have saved me the time. We have solar PV, Tesla Powerwall, Mixergy hot water tank, ASHP and EV. On the Go tariff at 7.5p/kWh off-peak our savings to date have been superior to other beta tariffs. With the imminent increase to 12p/kWh this isn’t so obvious, but your results mostly confirm my intuition. I suspect the Go tariff still represents best value for money in our case, though I can now check this by tweaking your spreadsheet.
Another thing that could be factored in to this amazing spreadsheet is, something like Ripple wind farm data, I am part of the Kirk Hill which is still being built, so it might be a little while before we get any data that can be added in, but again, weather related.
Yep, I had half a look on Ripple's first project, and it looks to be doing OK, especially now they have just re negotiated the price to 28p/KWh, so I have signed up to the second project, they now have share options open for the third project, so maybe get in there this time. I just put £500 in which gave me a tiny 250W!
@@SheepShearerMike nice. Yeah, I've just used my spreadsheets to calculate how much we're missing once we account for PV generation. Might need as much as £2k!
@@TimAndKatsGreenWalk Please do a video on Ripple Energy Tim!! My whole upgrade for Solar, PV, EV and heat pump is literally hanging on your word. The wife keeps asking me who this Tim person is as I keep talking about you more than my own mates!!
Impressive amount of work. I'll need to watch this video several times, but one quick observation: I think you said that 30 miles in an EV would require 3.6kWh per day. I think that may be incorrect. Assuming 3 miles per kWh, there would be a daily requirement of 10kWh, increased to 11kWh to cover inverter losses depending on the car?
30 miles three times a week, total 90 miles. Fiat 500e should get 4+ miles per kWh, so I've assumed 3.5, which then requires an average charge of about 3.6 kWh per night for seven nights.
@Tim & Kat's Green Walk OK, depending upon your solar size/output Cosy may be the way to go because Go exports are paid 4p/kWh, Cosy 15p/kWh. Also, some battery controllers may be incapable of programming two off-peak sessions per day, and in winter incapable of fully charging in a three hour period. My domestic Tesla prefers to charge at 3.5kW, which would be inadequate even when I keep a 20% reserve. Lots to consider, how will most people cope with this stuff?
@@CheshireRing yeah, it's very complicated. I didn't realise cosy export tariff was 15p though, that's interesting. I'll have to look into that. Once I've got enough solar data to build a decent model for that I'll get it added in to the spreadsheet and include export too for completeness. Should be interesting.
I would defer your decision on “Cosy” until after a solar/battery install. Choice depends on your Off Peak/ On Peak ratio….and with a well thought out battery capacity would change your ‘stats’ dramatically .
Well, exactly, that's the whole point of this spreadsheet. You can see how changing the battery capacity changes the results a lot. As it happens I've just added solar generation (or rather a proxy for it) to this spreadsheet and will be doing an update soon, hopefully. The short answer is that adding solar makes it even more clear that sticking with Go is the right choice for us.
This is all good info Tim, well done on all the hard work behind it. It is amazing what data you can get for free, such as 20yrs of weather data 🤯 And now, your spreadsheet! 😁 Thank you. Once you get the solar, it will be good to see how that changes things. All this data must be similar to how the Homely Smart Thermostat works.
That is a beast of a spreadsheet. Gradually working my way around it & I am really impressed. However, I think people should consider a few extra factors if they are using this to make quite a big investment decision: (1) The round trip efficiency of the battery should be considered (as you highlight in the video). Tesla Powerwall 2 specs suggest this is 90%. I guess it is probably similar for others. (2) Battery degradation needs to be considered. If you do continually discharge it fully every day I think there is likely to be a noticeable drop off after a few years. Tesla Powerwall 2 warranty is 70% at 10 years. (3) You should do some comparisons against historic electricity rates. I don't think we will get back to 2019 prices but I think things will come down a bit in a couple of years. This kind of sensitivity study will let you assess how at risk your return will be. (4) When comparing saving/pay back you should take a leaf out of the bullseye approach and "Let’s have a look at what you could have won". Probably best to just consider the return from a fixed rate savings account (3 to 4% per year) or mortgage rate (as instead of buying a battery most people could instead reduce their mortgage). (5) I think you should highlight that cost comparisons to no battery should be against the cheapest tariff with no battery rather than just assuming no battery is on the standard tariff. Personally, I am not convinced batteries really add up, they certainly don't on the couple of indicative quotes I have had (but perhaps you have got a much better deal). I will be very interested to see if an assessment of solar + batteries would change this. The only other aspect I am concerned about is the environmental impact of batteries which doesn't really get talked about much. Unless there is a strong financial argument or a need for secure supplies I am not sure typical homeowners should really be installing them. Once again, great work and I look forward to your next instalment...
Batteries help reduce the amount of grid import you use when combined with solar, so you are reducing your emissions by having one. If you get a LFP battery they are fully recyclable at end of life (unlike NMC batteries like the powerwall) which helps reduce their lifetime impact too, so overall a battery will have a net benefit on the environment. They definitely pay for themselves too, with or without solar, but if you have solar it's a no brainer getting a battery too, imo.
I’d like to see an up to date lifecycle analysis. As grid decarbonises the battery benefit reduces. I have not seen any good recent studies. I also hope that in the next few years I can use the battery in an EV to feed the home at peak times so no need for a separate battery. Would love to know who you are getting your system from though as you must be getting a better deal than I have seen. I’m a little north of Bristol so should be in range of your installer.
@@AndrewMacleod-nx6iz vehicle to load is all fine and well if you're parked at home all the time. They have their place for sure. But dedicated home batteries are more flexible. You should be able to get a 9.5 kWh GivEnergy battery for about £4-5k which should pay for itself well within the 10 year expected lifetime. Our installer is called B-line project services.
The batteries will have a useable life well beyond 10 years( the Guarantee length) . Maybe only 70% but still plenty. People must start considering the ROI on a new kitchen before they dismiss solar & batteries based on cost 👍
I've contacted GivEnergy to see what they say. Thanks for bringing that to my attention, if it turns out to be the case then there's no point me getting that 5.2 kWh battery. The question is then whether or not to get an extra 9.5 since I wouldn't be able to charge both up in 4 hrs.
Reply from GivEnergy: "Hi Tim, The charge and discharge speed is set by the inverter. The Gen 2 inverter can charge and discharge at a maximum of 3.6kWh. This 3.6kWh would be split over the two batteries so they could charge and discharge together." So it looks like because we'd have a 9.5 kWh battery as well it won't get throttled. Phew!
I've just had a look at a givenergy data sheet and it says the maximum charge/discharge is 50A at full voltage of 60V, that means it will only charge at 3kw, but then there's another data sheet that says maximum charge/discharge at 60A at 60V which is 3.6kw. They must know what they are doing lol Anyway the 2.6kwh is definitely a no no as that only charges at a max of 30A at 60V
P.S. all these are numbers are if the battery is at the maximum voltage of 60V, if the voltage is less for some reason then the Charge/discharge rate will drop unlike the 8.2 and 9.2 which the current is 80A thus will help if the voltage drops.
Oh, nice. What got me wondering was the requirement to have an MCS certificate ("We may ask you to provide the MCS certificate for your heat pump installation to confirm this"), which would be unusual for AC installers as most aren't MCS registered. Perhaps there could be other ways to prove it if it's A2A.
@@TimAndKatsGreenWalk just looked on the MCS site and air-to-water and air-to-air appear to be covered, bottom line i guess is technically an air-to-air system would need to be installed by an MCS registered installer to get the cert as it seems to be verifying the design (and install?)
@@garygoesgreen yes, exactly. At present most A2A installers haven't even heard of MCS certification though! So worth making sure they are in that case (something I hadn't considered when choosing ours, annoyingly).
Bear in mind your own daily peaks and troughs and how that plays in to how long your battery lasts each day: beleive me having another opportunity to top up your battery again part way through a low solar days before heading into the evening would be a god send on the winter side of the equinoxes.
Yeah, there are a lot of simplifications in this. It's not intended to be super accurate, just give an idea of what are the important factors to consider. I'd like to do a full half hourly model at some point but getting hold of that level of data is a big task and probably wouldn't change the results a huge amount.
Great video and a totally awesome and very useful spreadsheet, some thoughts, Battery size versus how much much can you actually fill it up as it may only be able to do so much with the cosy time slot. so if you have 20 kwh might only get 9kWh charge capacity so maybe have an input for how fast the inverter can charge the batteries per house (most setups might only be 3.5kWh per hour) .
Great stuff and very interesting but I suspect your car would use a higher number of KWhr than specified which I suspect of the top of my head would bias an even bigger saving to the go tariff.
I'm pretty confident about my value. It's a Fiat 500e so should do 4-5 miles per kWh. I've assumed 3.5 miles per kWh for my estimate to be on the safe side. Plenty of contingency.
@@TimAndKatsGreenWalk I did a Go/Intelligent comparison on my real time usage a few weeks ago prior to my Octopus contract changing and the intelligent worked out at 22p KWh average and the go worked out at 33p KWh average at the new pricing. Obviously it depend on the usage pattern but there are a few live spread sheets on Octopus threads that let you do this easily which download two days usage at a time. Love the air con vids as I'm in the process of getting an estimate for a 4* split Toshiba system. I suspect the "should do 4-5 miles per kWh" will probably be good for the summer but Its a total different ball game in the winter even with a heat pump car. My Tesla three with a heat pump is generally in the 3mile a kw range in the winter months and its noted as being one of the most efficient although your motoring costs will be minuscule compared to an ICE vehicle.
Hi Tim, Interesting. What's your battery charge rate in kW? Is it the GivEnergy 3kW? If so you can charge up to 12kWh on Go or 18kWh (2x9kWh) on Cozy which isn't double but I believe there's a Gen 2 version with double BMS 9.5kWh rated at 0.5C 1C charge and discharge so 4.25kW giving full 9.5kWh on Go and 19kWh (2x9.5kWh) on Cozy with one battery unit which is double - but it depends if it discharges to give room for the second Cozy period. You'll likely often find with solar that the second period can't be utilised, depending on how much solar of course. I have a Huawei hybrid which can charge the 15kWh battery at 5kW from solar and simultaneously give 6kW to AC but is limited at present to 3kW charge from AC and 5kW discharge. I'm trying to improve the AC charge rate. In your calculations did you account for house consumption at cheap rate during battery charge as well as no house grid consumption up to battery maximum output whilst running off battery fully? Tricky with the all that goes on and more so with solar added in.
Yeah, it's complicated and there are simplifications. The GivEnergy gen 2 hybrid inverters can charge and discharge at 3.6 kW so enough for us. The reason for setting up the half hourly profiles is so house consumption during off-peak rate is accounted for properly. We're also assuming you don't exceed the battery discharge rate at any time, which is good enough for the vast majority of the time. As I say, this isn't designed to give a precise answer, that would be impossible, it's designed to give an approximate but informative answer to aid decision making.
@@TimAndKatsGreenWalk Ah it's a Gen 2 hybrid you have. When I spoke to GivEnergy about their original 5kW (gen 1) hybrid they told me the 5kW power rating was shared between AC output and battery charging/discharging, so if the house load was 5kW there'd be no battery charging or if 2.5kW house load the battery could be charged at 2.5kW etc. I'd presumed this was a limitation of having a 50V battery so requiring high to low voltage conversion in the hybrid. That's why I opted for the Huawei 6kW hybrid plus 15kWh battery system which can give 6kW AC whilst also simultaneously charging at 5kW into their high voltage battery from PV. The charging is all at high voltage managed by the battery BMS not the hybrid. What let me down was their AC charge rate being limited to 3kW which wasn't clear on the data sheet which claimed a 5kW maximum battery charge rate but that's DC from PV only as it turned out. For AC charging the hybrid generates DC and for some reason is limited to 3kW in software (buried in the installation manual). I've asked them why and if it can be increased. It all shows you have to be careful about data sheet specs! Anyway it might be worth asking GivEnergy if the same shared power limitation exists for their Gen 2 hybrid as their Gen 1 as when you get solar it could make a significant difference. As I mentioned previously I'd read on another supplier's website that the Gen 2 GivEnergy 9.5kW battery had a dual BMS (quoting 0.5C charge rate) so possibly the 5kW hybrid Gen 2 power is no longer shared - however I can't see mention of this on the GivEnergy website so it might have been that supplier's special. The GivEnergy technical support is very good though and will I'm sure clarify.
@@johnh9449 yes, interpreting data sheets is a bit of a dark art, for sure. This is why having real world examples available for people to see is really important and partly why I started this channel. Once we have all the equipment installed (we don't have it just yet but it is incoming soon) I'll be sure to do lots of testing and show all that on the channel for others to learn from.
Nice work Tim, got to love a spreadsheet. In the situation where there is air to air heating cooling so you can use it to cool the home in the summer does that have an impact on it?🤔
I've not included that but yes, that will have an impact. I suspect it will be small though, as the AC will almost certainly be covered by excess solar generation, so that'll just reduce the amount of export. We don't yet know how much we'll be using the cooling in any case, so I'll revisit this question during the Summer, probably.
Quite possibly. The heating obviously dominates during winter and that's when solar production is at its lowest, maybe only a few kWh per day, so that only helps offset a small fraction of the total use. But yes, I will be adding that in just as soon as I have enough data to make a decent model for it.
@@TimAndKatsGreenWalk Winter production is terrible for me solar was 67kWh for December and so far in January its 62kWh ... I think due to the sun being so low in the sky during winter the level that the panels are at are perfect for summer but not so good in winter (if you could place them more upright then I guess I could get slightly more production). When you have your water daily rate of circa 5kWh I guess when you have solar you should be able to power that completely in the summer period with solar and if you get the ASHP solution then that would make it even more likely that you get free hot water.
You may have shown this but the videos are very detailed (serious work, well done!) but have you ever shared what the daily kwh use for the day looks like? Summer vs winter for example? I'm interested to know what I'd need to do with my battery system to run the heat pump off peak electricity (mainly during winter as little solar generated). I'd expect my system would be quite similar to yours.
I do a stats video every month, so you can see some more detailed values in those. I've also done a couple of recent spreadsheet videos showing strategies for running your heat pump based on heat loss and tariff, so check those out to find out how you can run your heat pump with minimal peak power (they're a bit long and detailed too, I'm afraid!).
Helpful stuff, looking at getting a Daikin Multi+ Air-2-Air heat pump (it does your water too), a PV array of about 6.7KW and a 10KW battery setup. Does anyone else have the Daikin Multi+?
We've just had a Daikin multi system installed, but chose to use the capacity the water "loop" would have used for room cooling/heating instead. The numbers didn't add up over time with solar excess and an Eddi instead, seemed a wasted opportunity to not just have more usage from air:air.
Tom great videos it was your advice I took and went for Givenergy. I just got 15 panels on an east west elevation with 9.5 battery and 5kw inverter both Gen 2. We are currently on a good tariff just now with octopus which is due to end in June so looking forward to ur flux comparison. Can you advise how I can get access to ur spreadsheets to see what would be.
Take a look in the description and you should find a link where you can grab a copy. I'll be attempting to do the Flux version at some point before Summer, hopefully, but it's gonna be tricky. By the way there is an updated version of this spreadsheet that includes solar, so check out the follow-up video to this one for the link to that instead.
@@TimAndKatsGreenWalk thank you will have a wee look at it and see how I get on! It’s early days for me but please with what I’m getting out of it. Just going to wait gor Givenergy to launch the EV caharger
@@TimAndKatsGreenWalk yes, Ive read that on other YT vids, but read the government guidance this morning and it only says air/water/ground source input heat pumps & doesn’t seem to distinguish between air or water on the output side ( www.gov.uk/apply-boiler-upgrade-scheme/print ). I bought a new gas boiler last year, just before Putin messed up the energy market, with old rads sized for 80C flow. I’m wondering how to mitigate my losses & A2A HP sounds good.
@@jorkirasalas2726 the crucial part is that the system needs to supply hot water as well as space heating to qualify. Most A2A only does heating, although I hear there are one or two that can do hot water too, so those might qualify. Ours does not, however, which is a shame.
@@jorkirasalas2726 yeah, it's sneaky. And unfair, I think. But then when has anything government related been consistent? Also, most AC installers are not MCS certified, they tend to only be f-gas registered. I suspect that might start changing in the future as more A2A systems become capable of providing hot water too and so would qualify for the BUS. We shall see.
What a great effort , well done. Unfortunately my system has an "intelligent" heat pump controller (Homely) which optimises heat pump activity for different tariffs, so I guess it would be virtually impossible to make a prediction spreadsheet. I don't know how common such controllers are. Anyone know?
@@TimAndKatsGreenWalk Thanks Tim , as you probably gathered from my flurry of comments I have only just discovered your channel! In fact it was the GivEnergy installer for my solar panels who sent me the first link saying you can explain the app and portal better than he can :) . But your videos are a great mine of info well beyond the GivEnergy stuff. My understanding of controllers and heat pumps: as we know, to work most efficiently they need to run for longer periods with the smallest dT that they can while still giving you the the room temperature you want. This depends on the weather. So for non-smart controllers the installer programs uses knowledge of your house (insulation etc) and average weather conditions throughout the year to program the heat pumps behaviour. With a device like Homely it does a more dynamic control using weather forecasts, outdoor temp, temperature of the return (talking air2water there) etc in order to work out when to turn on and how much power to use to achieve your heating goal most efficiently. I like the idea, but it is not quite as smart yet as you might imagine, however Homely continuously develop it and are very receptive to suggestions from their existing users.
@@mikeavison5383 that's very interesting. It sounds like a great idea in principle. I'm sure it'll get to the point where it's really beneficial, these things always take a while to mature. I'm glad you're finding the channel useful. That was my main aim when starting it, really, to see if it would be useful to share my experiences with others. It seems that's mostly that case, so I'm glad about that!
Tim's getting the spreadsheets out. A man after my own heart.
Whooooh.....opening line "I have another needs video for you today" ....
Paused whilst I get my mega popcorn bucket and slippers!
Wow, I’m super impressed with this - I admire the time and effort this must have taken you! What I’m really interested in doing when I get round to downloading my own copy is to take out the 3 hours of expensive heating on the Cosy tariff, and see how that changes the numbers. I think most people would simply avoid having the heating running for that peak time - if you’ve got a heat pump then the assumption would be that your house should be insulated well enough for the temperature not to drop significantly.
Thank you. Yes, you can do that by changing the number of peak heating hours in the green cell L16 to zero. That then doesn't use any heating during those three peak hours. It's fun to tinker with various settings to see what impact it has.
Thank you very much I will be tinkering around with this for days 👍👍👍
You're welcome.
First of all, what a great spreadsheet, so involved. I want to look at the intelligent Octopus and do have a very high use of electricity.
I have found with my Tesla Powerwall 13.5kWh and solar PV, summer is very cheap, but there is still a fair bit of use as it is not sunny all the time! As it reaches the winter, the bettery is filled overnight at cheap rate, around 3.3kWh per hour, so i find that I need a longer cheap rate, especially when adding in my EV charging. So, not to surprised at you result!
Yep, same here, Intelligent /Agile Octopus and high electric use. Problem is, Agile is 34p/kWh one minute and - 3.4p the next. Although I think it does work out that, the more wind there is, the cheaper it is, so can be factored in using the weather side of the graph too, maybe!
Tim, great work, taken a copy, a big TY for making it available. PV modelling would be the next logical progression for this, I seem to recall that the 20 year weather data had some form of Sun index in it?????? Apply a scaling factor to ones own installation, nudge nudge wink wink!! I know it's not where this started but... Also I know your limited on the number of panels you can fit but do they all have to fit on the roof?? Be great to play the whatif game with panels as you did with battery size 😁
Yup, that's absolutely the plan once I've got some solar generation data to compare to the solar energy index included in that data feed. It'd be good to have a complete system modelled, then this spreadsheet will be unstoppable.
Very helpful thanks! I’ve been meaning to do something similar myself but you have saved me the time. We have solar PV, Tesla Powerwall, Mixergy hot water tank, ASHP and EV. On the Go tariff at 7.5p/kWh off-peak our savings to date have been superior to other beta tariffs. With the imminent increase to 12p/kWh this isn’t so obvious, but your results mostly confirm my intuition. I suspect the Go tariff still represents best value for money in our case, though I can now check this by tweaking your spreadsheet.
If you've not spotted it I've done an update to this that includes solar, so check that out if you're interested.
Another thing that could be factored in to this amazing spreadsheet is, something like Ripple wind farm data, I am part of the Kirk Hill which is still being built, so it might be a little while before we get any data that can be added in, but again, weather related.
Yeah, that would be neat, although the wind data would need to be obtained for the turbine site for full effectiveness. Doable though.
Also, I really should investigate Ripple more. I took a brief look a couple of months ago but should give it some more attention.
Yep, I had half a look on Ripple's first project, and it looks to be doing OK, especially now they have just re negotiated the price to 28p/KWh, so I have signed up to the second project, they now have share options open for the third project, so maybe get in there this time. I just put £500 in which gave me a tiny 250W!
@@SheepShearerMike nice. Yeah, I've just used my spreadsheets to calculate how much we're missing once we account for PV generation. Might need as much as £2k!
@@TimAndKatsGreenWalk Please do a video on Ripple Energy Tim!! My whole upgrade for Solar, PV, EV and heat pump is literally hanging on your word. The wife keeps asking me who this Tim person is as I keep talking about you more than my own mates!!
Great man Tim
Impressive amount of work. I'll need to watch this video several times, but one quick observation: I think you said that 30 miles in an EV would require 3.6kWh per day. I think that may be incorrect. Assuming 3 miles per kWh, there would be a daily requirement of 10kWh, increased to 11kWh to cover inverter losses depending on the car?
30 miles three times a week, total 90 miles. Fiat 500e should get 4+ miles per kWh, so I've assumed 3.5, which then requires an average charge of about 3.6 kWh per night for seven nights.
@Tim & Kat's Green Walk OK, depending upon your solar size/output Cosy may be the way to go because Go exports are paid 4p/kWh, Cosy 15p/kWh. Also, some battery controllers may be incapable of programming two off-peak sessions per day, and in winter incapable of fully charging in a three hour period. My domestic Tesla prefers to charge at 3.5kW, which would be inadequate even when I keep a 20% reserve. Lots to consider, how will most people cope with this stuff?
@@CheshireRing yeah, it's very complicated. I didn't realise cosy export tariff was 15p though, that's interesting. I'll have to look into that. Once I've got enough solar data to build a decent model for that I'll get it added in to the spreadsheet and include export too for completeness. Should be interesting.
I would defer your decision on “Cosy” until after a solar/battery install. Choice depends on your Off Peak/ On Peak ratio….and with a well thought out battery capacity would change your ‘stats’ dramatically .
Well, exactly, that's the whole point of this spreadsheet. You can see how changing the battery capacity changes the results a lot. As it happens I've just added solar generation (or rather a proxy for it) to this spreadsheet and will be doing an update soon, hopefully. The short answer is that adding solar makes it even more clear that sticking with Go is the right choice for us.
Yessssssss game on 😊
super cool :)
A fellow sufferer of spreadsheetitis (I know, I don’t suffer from it, I enjoy it)
This is all good info Tim, well done on all the hard work behind it.
It is amazing what data you can get for free, such as 20yrs of weather data 🤯 And now, your spreadsheet! 😁 Thank you. Once you get the solar, it will be good to see how that changes things.
All this data must be similar to how the Homely Smart Thermostat works.
Yeah, I can't wait to get the solar data added to this. I suspect it may change things in unexpected ways.
That is a beast of a spreadsheet. Gradually working my way around it & I am really impressed. However, I think people should consider a few extra factors if they are using this to make quite a big investment decision:
(1) The round trip efficiency of the battery should be considered (as you highlight in the video). Tesla Powerwall 2 specs suggest this is 90%. I guess it is probably similar for others.
(2) Battery degradation needs to be considered. If you do continually discharge it fully every day I think there is likely to be a noticeable drop off after a few years. Tesla Powerwall 2 warranty is 70% at 10 years.
(3) You should do some comparisons against historic electricity rates. I don't think we will get back to 2019 prices but I think things will come down a bit in a couple of years. This kind of sensitivity study will let you assess how at risk your return will be.
(4) When comparing saving/pay back you should take a leaf out of the bullseye approach and "Let’s have a look at what you could have won". Probably best to just consider the return from a fixed rate savings account (3 to 4% per year) or mortgage rate (as instead of buying a battery most people could instead reduce their mortgage).
(5) I think you should highlight that cost comparisons to no battery should be against the cheapest tariff with no battery rather than just assuming no battery is on the standard tariff.
Personally, I am not convinced batteries really add up, they certainly don't on the couple of indicative quotes I have had (but perhaps you have got a much better deal). I will be very interested to see if an assessment of solar + batteries would change this. The only other aspect I am concerned about is the environmental impact of batteries which doesn't really get talked about much. Unless there is a strong financial argument or a need for secure supplies I am not sure typical homeowners should really be installing them.
Once again, great work and I look forward to your next instalment...
Batteries help reduce the amount of grid import you use when combined with solar, so you are reducing your emissions by having one. If you get a LFP battery they are fully recyclable at end of life (unlike NMC batteries like the powerwall) which helps reduce their lifetime impact too, so overall a battery will have a net benefit on the environment. They definitely pay for themselves too, with or without solar, but if you have solar it's a no brainer getting a battery too, imo.
I’d like to see an up to date lifecycle analysis. As grid decarbonises the battery benefit reduces. I have not seen any good recent studies. I also hope that in the next few years I can use the battery in an EV to feed the home at peak times so no need for a separate battery. Would love to know who you are getting your system from though as you must be getting a better deal than I have seen. I’m a little north of Bristol so should be in range of your installer.
@@AndrewMacleod-nx6iz vehicle to load is all fine and well if you're parked at home all the time. They have their place for sure. But dedicated home batteries are more flexible. You should be able to get a 9.5 kWh GivEnergy battery for about £4-5k which should pay for itself well within the 10 year expected lifetime. Our installer is called B-line project services.
Ah, yes at that price it works!
The batteries will have a useable life well beyond 10 years( the Guarantee length) . Maybe only 70% but still plenty. People must start considering the ROI on a new kitchen before they dismiss solar & batteries based on cost 👍
My understanding is that the 5.2kwh battery only charges/discharges at 2.5kwh thus your gen2 inverter becomes a gen1 inverter
Yeah but what about the 9.5 kWh battery? Surely that'll charge at 3.6 kW?
I've contacted GivEnergy to see what they say. Thanks for bringing that to my attention, if it turns out to be the case then there's no point me getting that 5.2 kWh battery. The question is then whether or not to get an extra 9.5 since I wouldn't be able to charge both up in 4 hrs.
Reply from GivEnergy:
"Hi Tim,
The charge and discharge speed is set by the inverter. The Gen 2 inverter can charge and discharge at a maximum of 3.6kWh. This 3.6kWh would be split over the two batteries so they could charge and discharge together."
So it looks like because we'd have a 9.5 kWh battery as well it won't get throttled. Phew!
I've just had a look at a givenergy data sheet and it says the maximum charge/discharge is 50A at full voltage of 60V, that means it will only charge at 3kw, but then there's another data sheet that says maximum charge/discharge at 60A at 60V which is 3.6kw.
They must know what they are doing lol
Anyway the 2.6kwh is definitely a no no as that only charges at a max of 30A at 60V
P.S. all these are numbers are if the battery is at the maximum voltage of 60V, if the voltage is less for some reason then the Charge/discharge rate will drop unlike the 8.2 and 9.2 which the current is 80A thus will help if the voltage drops.
I emailed octopus cust services when cosy came out and they confirmed that air-to-air heat-pumps qualified…. Hopefully that was an informed response 🤞
Oh, nice. What got me wondering was the requirement to have an MCS certificate ("We may ask you to provide the MCS certificate for your heat pump installation to confirm this"), which would be unusual for AC installers as most aren't MCS registered. Perhaps there could be other ways to prove it if it's A2A.
@@TimAndKatsGreenWalk yeah they didn’t mention that, sounds like its needed then or a lottery to sneak in like the EV requirement was
@@garygoesgreen yeah, I switched to Go without them asking about the EV, so it seems they only ask a random sample who apply.
@@TimAndKatsGreenWalk just looked on the MCS site and air-to-water and air-to-air appear to be covered, bottom line i guess is technically an air-to-air system would need to be installed by an MCS registered installer to get the cert as it seems to be verifying the design (and install?)
@@garygoesgreen yes, exactly. At present most A2A installers haven't even heard of MCS certification though! So worth making sure they are in that case (something I hadn't considered when choosing ours, annoyingly).
Bear in mind your own daily peaks and troughs and how that plays in to how long your battery lasts each day: beleive me having another opportunity to top up your battery again part way through a low solar days before heading into the evening would be a god send on the winter side of the equinoxes.
Yeah, there are a lot of simplifications in this. It's not intended to be super accurate, just give an idea of what are the important factors to consider. I'd like to do a full half hourly model at some point but getting hold of that level of data is a big task and probably wouldn't change the results a huge amount.
Great video and a totally awesome and very useful spreadsheet, some thoughts, Battery size versus how much much can you actually fill it up as it may only be able to do so much with the cosy time slot. so if you have 20 kwh might only get 9kWh charge capacity so maybe have an input for how fast the inverter can charge the batteries per house (most setups might only be 3.5kWh per hour) .
Yup, I mentioned that in the video a couple of times. That is definitely something to consider.
Great stuff and very interesting but I suspect your car would use a higher number of KWhr than specified which I suspect of the top of my head would bias an even bigger saving to the go tariff.
I'm pretty confident about my value. It's a Fiat 500e so should do 4-5 miles per kWh. I've assumed 3.5 miles per kWh for my estimate to be on the safe side. Plenty of contingency.
30 miles three times a week so 90 miles per week.
@@TimAndKatsGreenWalk I did a Go/Intelligent comparison on my real time usage a few weeks ago prior to my Octopus contract changing and the intelligent worked out at 22p KWh average and the go worked out at 33p KWh average at the new pricing. Obviously it depend on the usage pattern but there are a few live spread sheets on Octopus threads that let you do this easily which download two days usage at a time. Love the air con vids as I'm in the process of getting an estimate for a 4* split Toshiba system. I suspect the "should do 4-5 miles per kWh" will probably be good for the summer but Its a total different ball game in the winter even with a heat pump car. My Tesla three with a heat pump is generally in the 3mile a kw range in the winter months and its noted as being one of the most efficient although your motoring costs will be minuscule compared to an ICE vehicle.
@@TimAndKatsGreenWalk 3.5 m/kwh errs nicely on the side of caution from my experience of an MG4
Hi Tim,
Interesting. What's your battery charge rate in kW? Is it the GivEnergy 3kW? If so you can charge up to 12kWh on Go or 18kWh (2x9kWh) on Cozy which isn't double but I believe there's a Gen 2 version with double BMS 9.5kWh rated at 0.5C 1C charge and discharge so 4.25kW giving full 9.5kWh on Go and 19kWh (2x9.5kWh) on Cozy with one battery unit which is double - but it depends if it discharges to give room for the second Cozy period. You'll likely often find with solar that the second period can't be utilised, depending on how much solar of course.
I have a Huawei hybrid which can charge the 15kWh battery at 5kW from solar and simultaneously give 6kW to AC but is limited at present to 3kW charge from AC and 5kW discharge. I'm trying to improve the AC charge rate.
In your calculations did you account for house consumption at cheap rate during battery charge as well as no house grid consumption up to battery maximum output whilst running off battery fully? Tricky with the all that goes on and more so with solar added in.
Yeah, it's complicated and there are simplifications. The GivEnergy gen 2 hybrid inverters can charge and discharge at 3.6 kW so enough for us. The reason for setting up the half hourly profiles is so house consumption during off-peak rate is accounted for properly. We're also assuming you don't exceed the battery discharge rate at any time, which is good enough for the vast majority of the time. As I say, this isn't designed to give a precise answer, that would be impossible, it's designed to give an approximate but informative answer to aid decision making.
@@TimAndKatsGreenWalk Ah it's a Gen 2 hybrid you have. When I spoke to GivEnergy about their original 5kW (gen 1) hybrid they told me the 5kW power rating was shared between AC output and battery charging/discharging, so if the house load was 5kW there'd be no battery charging or if 2.5kW house load the battery could be charged at 2.5kW etc. I'd presumed this was a limitation of having a 50V battery so requiring high to low voltage conversion in the hybrid. That's why I opted for the Huawei 6kW hybrid plus 15kWh battery system which can give 6kW AC whilst also simultaneously charging at 5kW into their high voltage battery from PV. The charging is all at high voltage managed by the battery BMS not the hybrid. What let me down was their AC charge rate being limited to 3kW which wasn't clear on the data sheet which claimed a 5kW maximum battery charge rate but that's DC from PV only as it turned out. For AC charging the hybrid generates DC and for some reason is limited to 3kW in software (buried in the installation manual). I've asked them why and if it can be increased. It all shows you have to be careful about data sheet specs!
Anyway it might be worth asking GivEnergy if the same shared power limitation exists for their Gen 2 hybrid as their Gen 1 as when you get solar it could make a significant difference. As I mentioned previously I'd read on another supplier's website that the Gen 2 GivEnergy 9.5kW battery had a dual BMS (quoting 0.5C charge rate) so possibly the 5kW hybrid Gen 2 power is no longer shared - however I can't see mention of this on the GivEnergy website so it might have been that supplier's special. The GivEnergy technical support is very good though and will I'm sure clarify.
@@johnh9449 yes, interpreting data sheets is a bit of a dark art, for sure. This is why having real world examples available for people to see is really important and partly why I started this channel. Once we have all the equipment installed (we don't have it just yet but it is incoming soon) I'll be sure to do lots of testing and show all that on the channel for others to learn from.
Nice work Tim, got to love a spreadsheet. In the situation where there is air to air heating cooling so you can use it to cool the home in the summer does that have an impact on it?🤔
I've not included that but yes, that will have an impact. I suspect it will be small though, as the AC will almost certainly be covered by excess solar generation, so that'll just reduce the amount of export. We don't yet know how much we'll be using the cooling in any case, so I'll revisit this question during the Summer, probably.
The numbers are going to change so much when you have solar production added to the mix. Cosy for me as I dont have an EV
Quite possibly. The heating obviously dominates during winter and that's when solar production is at its lowest, maybe only a few kWh per day, so that only helps offset a small fraction of the total use. But yes, I will be adding that in just as soon as I have enough data to make a decent model for it.
@@TimAndKatsGreenWalk Winter production is terrible for me solar was 67kWh for December and so far in January its 62kWh ... I think due to the sun being so low in the sky during winter the level that the panels are at are perfect for summer but not so good in winter (if you could place them more upright then I guess I could get slightly more production). When you have your water daily rate of circa 5kWh I guess when you have solar you should be able to power that completely in the summer period with solar and if you get the ASHP solution then that would make it even more likely that you get free hot water.
You may have shown this but the videos are very detailed (serious work, well done!) but have you ever shared what the daily kwh use for the day looks like? Summer vs winter for example? I'm interested to know what I'd need to do with my battery system to run the heat pump off peak electricity (mainly during winter as little solar generated). I'd expect my system would be quite similar to yours.
I do a stats video every month, so you can see some more detailed values in those. I've also done a couple of recent spreadsheet videos showing strategies for running your heat pump based on heat loss and tariff, so check those out to find out how you can run your heat pump with minimal peak power (they're a bit long and detailed too, I'm afraid!).
@@TimAndKatsGreenWalk found that. Thanks! Look forward to your video on whether a bigger battery is worthwhile.
@@niallbenn yes, that's proving to be an interesting analysis. I'm keen to get the full set of data so I can finally answer that question!
Helpful stuff, looking at getting a Daikin Multi+ Air-2-Air heat pump (it does your water too), a PV array of about 6.7KW and a 10KW battery setup. Does anyone else have the Daikin Multi+?
That's interesting. I'd heard there were some A2A that did hot water too but hadn't looked into it much.
We've just had a Daikin multi system installed, but chose to use the capacity the water "loop" would have used for room cooling/heating instead. The numbers didn't add up over time with solar excess and an Eddi instead, seemed a wasted opportunity to not just have more usage from air:air.
Tom great videos it was your advice I took and went for Givenergy. I just got 15 panels on an east west elevation with 9.5 battery and 5kw inverter both Gen 2. We are currently on a good tariff just now with octopus which is due to end in June so looking forward to ur flux comparison. Can you advise how I can get access to ur spreadsheets to see what would be.
Take a look in the description and you should find a link where you can grab a copy. I'll be attempting to do the Flux version at some point before Summer, hopefully, but it's gonna be tricky. By the way there is an updated version of this spreadsheet that includes solar, so check out the follow-up video to this one for the link to that instead.
@@TimAndKatsGreenWalk thank you will have a wee look at it and see how I get on! It’s early days for me but please with what I’m getting out of it. Just going to wait gor Givenergy to launch the EV caharger
@@Jmbo65 yup, I'm waiting for that too. They're going to let me know when it's available.
Tim, did you get the UK government £5k payment when you changed over to your air to air heat pump?
The 5k grant only applies to air-to-water heat pump systems, unfortunately.
@@TimAndKatsGreenWalk yes, Ive read that on other YT vids, but read the government guidance this morning and it only says air/water/ground source input heat pumps & doesn’t seem to distinguish between air or water on the output side ( www.gov.uk/apply-boiler-upgrade-scheme/print ). I bought a new gas boiler last year, just before Putin messed up the energy market, with old rads sized for 80C flow. I’m wondering how to mitigate my losses & A2A HP sounds good.
@@jorkirasalas2726 the crucial part is that the system needs to supply hot water as well as space heating to qualify. Most A2A only does heating, although I hear there are one or two that can do hot water too, so those might qualify. Ours does not, however, which is a shame.
@@TimAndKatsGreenWalk thanks Tim! Hadn’t spotted that bit!
@@jorkirasalas2726 yeah, it's sneaky. And unfair, I think. But then when has anything government related been consistent? Also, most AC installers are not MCS certified, they tend to only be f-gas registered. I suspect that might start changing in the future as more A2A systems become capable of providing hot water too and so would qualify for the BUS. We shall see.
What a great effort , well done. Unfortunately my system has an "intelligent" heat pump controller (Homely) which optimises heat pump activity for different tariffs, so I guess it would be virtually impossible to make a prediction spreadsheet. I don't know how common such controllers are. Anyone know?
Good question, I've never heard of such a controller myself. By the way, I've got some more recent tariff videos that might interest you.
@@TimAndKatsGreenWalk Thanks Tim , as you probably gathered from my flurry of comments I have only just discovered your channel! In fact it was the GivEnergy installer for my solar panels who sent me the first link saying you can explain the app and portal better than he can :) . But your videos are a great mine of info well beyond the GivEnergy stuff. My understanding of controllers and heat pumps: as we know, to work most efficiently they need to run for longer periods with the smallest dT that they can while still giving you the the room temperature you want. This depends on the weather. So for non-smart controllers the installer programs uses knowledge of your house (insulation etc) and average weather conditions throughout the year to program the heat pumps behaviour. With a device like Homely it does a more dynamic control using weather forecasts, outdoor temp, temperature of the return (talking air2water there) etc in order to work out when to turn on and how much power to use to achieve your heating goal most efficiently. I like the idea, but it is not quite as smart yet as you might imagine, however Homely continuously develop it and are very receptive to suggestions from their existing users.
@@mikeavison5383 that's very interesting. It sounds like a great idea in principle. I'm sure it'll get to the point where it's really beneficial, these things always take a while to mature. I'm glad you're finding the channel useful. That was my main aim when starting it, really, to see if it would be useful to share my experiences with others. It seems that's mostly that case, so I'm glad about that!