Hi, Watched your spreadsheet analysis with interest, it's useful as a yardstick, but imperfect for the following reasons. 1. Solar generation bounces around minute by minute, it is also affected by the angle and time radiation hits your panels. So any analysis can only be considered as absolutes. 2. When you allow for batteries you are limited to not so much the capacity of the ure batteries but your charge rate and time you can access a low tariff. Your givenergy charge rate is 2.5 kw so the max charge in the cosy octopus would be 7.5kw twice a day. 3. Therefore a logical pattern to follow is:- 4am-7am charge batteries use battery power as the sunrises and the position changes your solar production peaks at midday, unless clouds interrupt. Generally your inverter will decrease battery as solar increases and takes more re of the load. 4. Next period 1pm to 4pm with luck you may have some charge in your battery. Let's say 1kw you can then use your solar and charge your battery the inverter will switch between the two. After 4pm you will have 1kw from am and 7.5 kw from pm this provides the power to supply you for the next three hours with luck. 5. So you can access 15 is of off peak using give energy plus whatever your pump etc uses during those off peak periods. Essentially being able to charge your batteries at off peak immediately before the peak period is the major advantage of octopus cosy. That is something you can't factor for in, there are too many variables. Further, think about payback in this way:- ask yourself how much would you have to earn to put say the cash equivalent of say 1000 kwhours. Given a cost per kwhr of ,36p that's £350 if your tax rate is 20% that's equivalent to £410 before tax thats ignoring NI and higher rate tax. Keep up the good work
Yeah, I said it was not a perfect representation. I'm going to be making a better one that runs at hourly resolution in due course. That will also be an imperfect representation for other reasons. All models are wrong but some are useful.
Nice work and good to see I’am not the only one geeking out on spreadsheets. Solar production in spring is also higher in comparison to autum due to solar panels being more efficient at the lower temperatures in spring.
Ah, yes, that's a good point and not something I account for at all in this spreadsheet. It'll be interesting to see how my panels perform in different temperatures when I get them in a few weeks. There's another spreadsheet video in that for sure.
Thanks for putting in the leg-work, with the nice graph at the end. It seems like a programming-language based 1/2 hours-step simulation is definitely the next iteration; then the Octopus Flux will just fall out, plus other constraints (battery capacity and charge/discharge rates, charge strategies) will be easier to implement. 12 years of data is only 210k cycles of simulation, so should be quick to run. Good luck!
Yup, coding is my bread and butter so I'm very tempted to go down that route. I think half hourly is really the only way to do this properly, it's getting hold of the historical data for the calculation that's gonna be the issue. Since I don't yet have data of my own for the solar it'll still be an approximation but hopefully better than nothing.
Once we get our PV and battery I'll be using an eddi to heat the hot water by excess solar or overnight grid via an immersion heater in the cylinder (there's a cell to enter your much you'd use per day in the spreadsheet). I'm hoping in a few years to replace that with a heat pump hot water cylinder when the existing cylinder needs replacing.
Hi Tim & Kat do you know if all of the octopus tariffs are available for properties with 3 phase supply, or are they only for homes with single phase? Cheers and keep up the great work with the videos!
Hi Tim, Another interesting one. Your solar graph looks very much like my solar versus heat pump load graph only I use averages and you've got noise but very similar. Where the lines cross over determines your optimal battery size in your case around 10kWh by the look of it just from solar. You can always make use of more capacity if you add off peak grid charging of course. I've got more load so my optional is 15-20kWh but I went for 15kWh as 20kWh started another stack with BMS so wasn't so cost effective. By the way, rather than pay back time I favour looking at it as a percentage return on investment. Solar plus battery alone can easily give you a 20% return on investment per annum - yes that pays back in five years but rather appreciate it gives you a 20% return for life and where can you earn that these days from your savings? And yes combining solar + battery with a heat pump is the killer.
The daily variation makes a big difference so is worth considering. Those days where the heating demand spikes up really high can have a disproportionate effect on the cost. But any sort of calculation is better than none, for sure.
@@TimAndKatsGreenWalk Yes daily variations are significant on the day and I've seen some interesting ones. I used the PV provider and heat pump provider heat loss monthly average figures to calculate the average day for that month figures plotted for the year to simplify things. So far since November It's a reasonable match to the grid total, peak and off-peak - as you might expect from averages dominated by the heat pump load. I've yet to see how summer works out where the PV will dominate. I started the spread sheet to work out battery capacity ( where the lines cross over) which is April and October and 15kWh for me but since then the spreadsheet has expanded. I've based it on Go but I'm looking at including the Flux tariff now for comparison. It will be interesting to see how it compares with your analysis. All very interesting stuff.
Are you planning to add the Flux tariff to your spreadsheet? I am expecting Solar in the next 2 months and am struggling with Flux now to decide which tariff is going to work out the best. Our system was to be 10.2 kW so that would throw out the Flux tariff unless I reduce the size back down below 9kW. We will have 17.6kW of battery so likely to have scope to export only during that 3 hour high demand period.
Flux is going to require a more complicated hourly spreadsheet, this daily one isn't going to cut it, I fear. I've got the historical hourly data, I just need to build the spreadsheet around that now. Easier said than done, mind. It is my plan to get to it at some point but I can't promise when, I'm afraid. Our install is happening right now so I'm going to be busy with that in the near term and there are many videos on my backlog.
Curious to know if you looked at E7? Like Cosy you can get 15p export, and you get a much longer off-peak period that now is not dissimilar to the Go costs (I believe, don’t have Go). I’m getting a 9.5 battery installed on top of my solar, no electric car, and part of house can be heated on A2A. Trying to figure out whether E7 or Flux will be better. Looks like the ideal will be Flux in sunny months for high export prices and then E7 in winter. I have to say I’m surprised the battery is enough to solely heat via A2A given the heating demand in winter, but I think your property may use quite a bit less than mine.
I've not looked into E7, to be honest, I probably should. I agree Flux could be good in the Summer but probably not ideal in Winter. The batteries won't cover all the heating by any means but for a good chunk of the Winter it'll cover a fair bit, with a couple of months needing some top up using peak rate power. I'm happy with that as a compromise. If battery prices come down I can easily add more, but then the issue will be actually charging it all up overnight given the charging rate limit. Everything is a compromise!
Very interesting - thanks! Have you done any comparisons with Octopus Tracker (Daily rates)? Rates since Jan1 this year have consistently averaged around 24% less than standard rates. Looks to me as if the ideal might be to be on Octopus Tracker during heating season (say Nov to May) & Flux Jun to Oct if you have PV solar, batteries & ASHP Currently they're only making Tracker available to 50 new customers per day and its on up to 6 months waiting list due to overwhelming demand. Hopefully will reopen properly soon.
No, I've not looked into Tracker. There are so many tariffs right now, it's hard to keep up! I think you're right about Flux for the Summer but something else for the Winter (Go for us probably).
@@TimAndKatsGreenWalk Tracker has averaged 24.3p inc vat since 1st Jan - saving 28.8% vs standard capped rates. Highest daily rate 31.05p. Lowest daily rate 17.42p. No wonder they've been inundated with requests to get on it! They don't highlight it as a tariff they offer!
I think that just goes to show more and more I need an EV! I have almost a years actual data from my solar system and five years from my friends so shall play around with this.
Ah, lovely data. Yeah, of course the other benefit of the EV is that you no longer need to spend money on petrol/diesel. We reckon we'll save about £50 a month on petrol by charging at home using overnight rate or solar.
Have you calculated the saving by charging the batteries from the grid in the off peak periods, and then using the stored energy in peak charge periods?
Yes, that's what I assume happens in this spreadsheet. It's not actually the optimum strategy for either of these tariffs however, since you'd be better off charging the battery with excess solar if you know the day to come is going to give you more solar than you can use, so this spreadsheet is a conservative estimate of the savings. This was the easiest way for me to calculate things on a daily basis, but to get a better value I'll need to break it down hourly and set up charging schedules for different times of the year etc. That's a work in progress.
@@TimAndKatsGreenWalk I have in the last week transferred to Octopus Intelligent, which gives me 6 hours of off peak electricity (23:30 to 05:30) and I have 3 x 8.2kWh GivEnergy batteries. The solar panels are set for 1) house use, 2) hot water, 3) battery, 4) vehicle charging, and finally 5) grid export. The batteries are set to accept solar generation, and then to download from the grid during the stated off peak period to 100%. So even in the depths of winter when the solar generation is minimal, I'm maximising the use of direct and stored off peak electricity.
Hi Tim I have done some similar calculations and also found that Go/Intelligent was the better option until the 15p on export that you definitely can get on Cosy into account compared to the 4.1p on Go/Intelligent.
Yup, I added the option for different export tariffs to the spreadsheet last night as I hadn't realised you could get a higher rate on Cosy. That actually made Cosy very slightly cheaper for the Summer, ironically.
Yes we have a big solar array and no battery and also found that cosy would be better in the summer and Go/intelligent in the winter. Do you know how easy it is to switch between the two?
@@Willy_Eckerslyke I hear that it's pretty straightforward to switch tariffs with Octopus so maybe it's worth doing. The downside is that if the tariffs go up you might find your existing one is better. Good to have a spreadsheet to work it out!
@@TimAndKatsGreenWalk I'm not 100% sure, but I think that GO/Intelligent/Cosy/Flux aren't fixed any more i.e. they are variable tariffs based on the current Octopus Flexible rates???
Really interesting Tim. I would be interested to know what payback difference it makes for the extra battery you added vs the original 9.5kW. I appreciate that the SS is making all sorts of assumptions but a comparison between the two battery sizes would be interesting. Like you I'm toying with adding more capacity to my original 9.5kW GivEnergy battery before it gets installed to take advantage of the 0% Vat.
£627 per year (on Go) with 13.5 kWh, £760 per year with 9 kWh (assuming 5% kept back from the 9.5 kWh battery). So the payback period becomes 13 years, rather than 12. The extra battery only saves about £130 per year, so arguably it's not worth getting if it costs more than about £1.5k. I think the cost of a 5.2 kWh battery is about £2k, so it's not likely to quite pay for itself, although adding that extra capacity might extend the life of the 9.5 kWh battery by a bit, so perhaps it's just about worthwhile? Also, Kat is happy about the fact that we can run the heating a bit more with the extra capacity, perhaps, so that's how I've sold her on the idea. Plus it gives you a bit more time with power in the event of a power-cut.
@@TimAndKatsGreenWalk Thanks Tim. Very interesting. For you I can see why the extra battery capacity is a good thing for your A2A heat pump heating (& cooling) multi split system which you can keep running for longer without any grid power. Free cooling in the summer as well! I still have gas CH for a while yet & no EV yet either so I think I'll wait until I add A2Air HP heating / hot water & add the extra battery at that point along with some more panels if I can. Once again thanks for the info.
It pays off, sure, but I still think the monthly money in your pocket is the real value, assuming you don't have to take out a loan to afford it - which is why there really ought to be a national programme at least for local storage, as well as heat pumps and ideally solar for anywhere that can take it. But just about everywhere could have a battery of some sort. The more local storage there is, the greener the grid because the more options there will be for flexible off/on peak peak periods. If the whole grid was like that the monthly pocket benefits would likely reduce a bit but lordy the emission reductions on the national scale would be enormous. Could probably grow to 75% renewables just from reliably storing excess, never mind what happens if you add a solar roofing programme to add passive self generation.
I'm sure all that will come in time. The value for me is knowing I'm generating and using my own power. It just feels nice. I don't need the money in my pocket (I realise I'm lucky in that way, of course). Having that insurance against potential price rises is very handy though.
Thank you once again for the great information, question are you adding in the export potential of your production in the days you dont consume all the power ? On SEG its 15 per kWh. I cant remember but which video should I watch to see how much your total A2A solution was in cost ? I have someone coming round for a site visit next Thursday and keen to have a real life comparison especially due to the fact that I am going for the same type as you (Toshiba Haori) Ive looked at the rooms i want to cover and there will be a need for 8 units for 8 rooms that i want to heat with two of those rooms being fairly large 7.3m x 4.7m in size so im thinking that I should probably have to condensers on each end of the house with one condenser feeding one large room and 3 smaller rooms each so its evenly spread ? I would rather overspec that underspec so will be interested to see what the price would be but I cant remember how many you had installed and what the total cost was so i have at least a ball park figure for the install
Yes, the SEG is in there, although I think at the moment it's 4p/kWh (maybe 15 is a previous tariff, or am I out of date?). There is a cell you can enter that in, then any solar excess beyond what you use gets added as a credit to the total. The video you're after is the tour of our A2A system, the first of the series. Take a look at the chapter markers on the description and you should be able to jump straight to it.
@@TimAndKatsGreenWalk Yes I get it due to being on COSY which im really finding good value compared to what i had previously. Dont have an EV so cant use the OCT GO tariffs. Getting the 15p for export would based on my last years export without getting paid anything due to no smart meter would be equal to £112 which is pretty good and at least pays for tthe standing charge and a little bit extra back. One more question after viewing the A2A video would you mind letting me know the size of your largest room the Kitchen/dining/snug room ? just trying to see if thats equal to one of my rooms so i can figure size of A2A to place in it. The pricing is really good and I'll need 2 large units 1 medium and 5 smaller units Im hoping it will all be under 15k
@@TimAndKatsGreenWalk I think you can still get the 15p rate with Cosy? Not sure how much difference that makes as your charge only seems to have one export value in M3. I have removed the car from your charge and adjusted solar to .9 (that matched my data). I get told GO cost is £565 a year. When I change export to 15p Cosy drops to £236 a year. It also shows me Cosy is cheaper in Dec & Jan two of the main months of wanting heating.
hi Tim - your solar system spec seems similar to mine (battery at least) I've a givenergy 5.0 hybrid invertor generation 1 and a 9.5 battery, and a ready to be installed 5.2 battery. Make sure to ask for the gen 2 invertor for your installation as the throughput to the battery is 1kw higher that gen1 (you probably know already). My installer is coming back in a few weeks to swap out my Gen1 for Gen2 and wire up the 5.3 battery. Also my array is 4kwp south east, 3kwp north west. What orientation/size are your panels? We still have gas for heating. Have an EV with Zappi and Eddi.. all good so far. Our tarrifs are different (Dublin). Curious as well if you are including conversion from AC to DC DC to AC losses in your calcs? cheers Mick
Yeah, we're getting a Gen 2 inverter, I made sure about that. The array will be 7.1 kWp split equally between due East and West. I'm not accounting for conversation losses in this spreadsheet because it's only a few percent and would be present regardless of the tariff so when comparing between tariffs it doesn't make much difference and the calculation was already getting quite complicated!
Does this take into account battery degradation? 12 years is beyond the lifecycle expected from GivEnergy but still very impressive to get it all "cost neutral"
No, it doesn't account for battery degradation, I'm sort of using this to work out what tariff would be best for the next year or so, so decided adding degradation would be unnecessary extra complexity. So that would affect the payback calc a bit. Although the uncertainty in future price changes would be a significantly larger source of error!
@@TimAndKatsGreenWalk Solar panel degradation over 25 years standard I see used by all as 15% so if you ignored replacing battery & use same as solar panel then you would inbuild a base degradation. As every year solar production is different & every month or day .... just in build some base reduction
Not necessarily. They don't check everyone who applies for Go. We signed up last winter before we got an EV and it wasn't a problem. You might find you get lucky.
Car charging is in there already (I showed that in the previous video so skipped over it for this one). Flux is gonna take a lot of work but I'll see what I can do!
Great journey your on ... but as usual all about payback & cost on every channel I see which for base people mean little as suddenly it enters into our 2 Tesla cars use this & we have that & I am installing this new thing on trail. Not being negative just simple fact people choose there own energy provider & tariff that they can obtain & usually not linked to I have got every gadget under the sun simply to what they can afford. I have recently had solar installed & battery but also a voltage optimiser which converts mains from average 243V from mains to 220V as all appliances made have to work at 220V & this has made biggest saving everyday. Saving roughly 15% kWh coming in & also same coming from battery so double win.
Man, I can't win. I don't really care about the payback but if I don't mention it all I get are comments about "what's the payback?". It seems a lot of folks really care about that so I have to mention it, I'm afraid.
Nice; Payoff - around 11:14 - That ~2k / year direct into batteries The solar is a bonus in summer, but batteries appear to be a no-brainer to time shift Octopus go cheap rate to the day time. Well that was my gut feel anyway - to invest savings from the govt. electric subsidy + above thinking into 17kWh of battery storage. To my mind the only issue to mitigate is longevity/stability of the battery solution so perhaps a phased purchase from different batches/vendors to even that out. Personally I'm sticking with go anyway because: 1. EV - only at home overnight so needs those 4 off peak hours 2. Solar is west facing so only starting to see the sun now until Sept - and even then only from lunchtime => potentially means simple setup year round: Fill the batteries overnight, they're approx @ 60% after breakfast/electric showers etc, ready for solar to top them up again in the afternoon. If its a sunny day - the next overnight will need less topup - so sort of run the batteries full rather than leave space for potential sun tomorrow.
Hi,
Watched your spreadsheet analysis with interest, it's useful as a yardstick, but imperfect for the following reasons.
1. Solar generation bounces around minute by minute, it is also affected by the angle and time radiation hits your panels. So any analysis can only be considered as absolutes.
2. When you allow for batteries you are limited to not so much the capacity of the ure batteries but your charge rate and time you can access a low tariff. Your givenergy charge rate is 2.5 kw so the max charge in the cosy octopus would be 7.5kw twice a day.
3. Therefore a logical pattern to follow is:- 4am-7am charge batteries use battery power as the sunrises and the position changes your solar production peaks at midday, unless clouds interrupt. Generally your inverter will decrease battery as solar increases and takes more re of the load.
4. Next period 1pm to 4pm with luck you may have some charge in your battery. Let's say 1kw you can then use your solar and charge your battery the inverter will switch between the two. After 4pm you will have 1kw from am and 7.5 kw from pm this provides the power to supply you for the next three hours with luck.
5. So you can access 15 is of off peak using give energy plus whatever your pump etc uses during those off peak periods. Essentially being able to charge your batteries at off peak immediately before the peak period is the major advantage of octopus cosy. That is something you can't factor for in, there are too many variables.
Further, think about payback in this way:- ask yourself how much would you have to earn to put say the cash equivalent of say 1000 kwhours. Given a cost per kwhr of ,36p that's £350 if your tax rate is 20% that's equivalent to £410 before tax thats ignoring NI and higher rate tax.
Keep up the good work
Yeah, I said it was not a perfect representation. I'm going to be making a better one that runs at hourly resolution in due course. That will also be an imperfect representation for other reasons. All models are wrong but some are useful.
Thank you most interesting as I'm considering the same options
Nice work and good to see I’am not the only one geeking out on spreadsheets. Solar production in spring is also higher in comparison to autum due to solar panels being more efficient at the lower temperatures in spring.
Ah, yes, that's a good point and not something I account for at all in this spreadsheet. It'll be interesting to see how my panels perform in different temperatures when I get them in a few weeks. There's another spreadsheet video in that for sure.
Great, detailed analysis. Really enjoying your videos since air conditioning. Subscribed
Thanks for putting in the leg-work, with the nice graph at the end. It seems like a programming-language based 1/2 hours-step simulation is definitely the next iteration; then the Octopus Flux will just fall out, plus other constraints (battery capacity and charge/discharge rates, charge strategies) will be easier to implement. 12 years of data is only 210k cycles of simulation, so should be quick to run. Good luck!
Yup, coding is my bread and butter so I'm very tempted to go down that route. I think half hourly is really the only way to do this properly, it's getting hold of the historical data for the calculation that's gonna be the issue. Since I don't yet have data of my own for the solar it'll still be an approximation but hopefully better than nothing.
That low rate for go is just so powerful.
Yup.
Well done Tim another great video. Glad to see someone doing what I want to do. How are you heating your water?
Once we get our PV and battery I'll be using an eddi to heat the hot water by excess solar or overnight grid via an immersion heater in the cylinder (there's a cell to enter your much you'd use per day in the spreadsheet). I'm hoping in a few years to replace that with a heat pump hot water cylinder when the existing cylinder needs replacing.
@@TimAndKatsGreenWalk I plan on getting the dimplex ASHP water tank with my A2A install so I'll be sure to let you know
@@bobbazley5376 I will be super interested to hear how you get on with that.
Hi Tim & Kat do you know if all of the octopus tariffs are available for properties with 3 phase supply, or are they only for homes with single phase? Cheers and keep up the great work with the videos!
I assume they're all available for three phase too. Best check with them though to be sure.
Hi Tim,
Another interesting one. Your solar graph looks very much like my solar versus heat pump load graph only I use averages and you've got noise but very similar. Where the lines cross over determines your optimal battery size in your case around 10kWh by the look of it just from solar. You can always make use of more capacity if you add off peak grid charging of course. I've got more load so my optional is 15-20kWh but I went for 15kWh as 20kWh started another stack with BMS so wasn't so cost effective.
By the way, rather than pay back time I favour looking at it as a percentage return on investment. Solar plus battery alone can easily give you a 20% return on investment per annum - yes that pays back in five years but rather appreciate it gives you a 20% return for life and where can you earn that these days from your savings? And yes combining solar + battery with a heat pump is the killer.
The daily variation makes a big difference so is worth considering. Those days where the heating demand spikes up really high can have a disproportionate effect on the cost. But any sort of calculation is better than none, for sure.
@@TimAndKatsGreenWalk Yes daily variations are significant on the day and I've seen some interesting ones. I used the PV provider and heat pump provider heat loss monthly average figures to calculate the average day for that month figures plotted for the year to simplify things. So far since November It's a reasonable match to the grid total, peak and off-peak - as you might expect from averages dominated by the heat pump load. I've yet to see how summer works out where the PV will dominate. I started the spread sheet to work out battery capacity ( where the lines cross over) which is April and October and 15kWh for me but since then the spreadsheet has expanded. I've based it on Go but I'm looking at including the Flux tariff now for comparison. It will be interesting to see how it compares with your analysis. All very interesting stuff.
@@johnh9449 yes, always worth an independent check, for sure.
Are you planning to add the Flux tariff to your spreadsheet?
I am expecting Solar in the next 2 months and am struggling with Flux now to decide which tariff is going to work out the best. Our system was to be 10.2 kW so that would throw out the Flux tariff unless I reduce the size back down below 9kW. We will have 17.6kW of battery so likely to have scope to export only during that 3 hour high demand period.
Flux is going to require a more complicated hourly spreadsheet, this daily one isn't going to cut it, I fear. I've got the historical hourly data, I just need to build the spreadsheet around that now. Easier said than done, mind. It is my plan to get to it at some point but I can't promise when, I'm afraid. Our install is happening right now so I'm going to be busy with that in the near term and there are many videos on my backlog.
Curious to know if you looked at E7? Like Cosy you can get 15p export, and you get a much longer off-peak period that now is not dissimilar to the Go costs (I believe, don’t have Go). I’m getting a 9.5 battery installed on top of my solar, no electric car, and part of house can be heated on A2A. Trying to figure out whether E7 or Flux will be better. Looks like the ideal will be Flux in sunny months for high export prices and then E7 in winter. I have to say I’m surprised the battery is enough to solely heat via A2A given the heating demand in winter, but I think your property may use quite a bit less than mine.
I've not looked into E7, to be honest, I probably should. I agree Flux could be good in the Summer but probably not ideal in Winter. The batteries won't cover all the heating by any means but for a good chunk of the Winter it'll cover a fair bit, with a couple of months needing some top up using peak rate power. I'm happy with that as a compromise. If battery prices come down I can easily add more, but then the issue will be actually charging it all up overnight given the charging rate limit. Everything is a compromise!
@@TimAndKatsGreenWalk with you on all these things! Exactly the same challenges I’ve been weighing up.
Very interesting - thanks! Have you done any comparisons with Octopus Tracker (Daily rates)? Rates since Jan1 this year have consistently averaged around 24% less than standard rates.
Looks to me as if the ideal might be to be on Octopus Tracker during heating season (say Nov to May) & Flux Jun to Oct if you have PV solar, batteries & ASHP
Currently they're only making Tracker available to 50 new customers per day and its on up to 6 months waiting list due to overwhelming demand. Hopefully will reopen properly soon.
No, I've not looked into Tracker. There are so many tariffs right now, it's hard to keep up! I think you're right about Flux for the Summer but something else for the Winter (Go for us probably).
@@TimAndKatsGreenWalk Tracker has averaged 24.3p inc vat since 1st Jan - saving 28.8% vs standard capped rates. Highest daily rate 31.05p. Lowest daily rate 17.42p. No wonder they've been inundated with requests to get on it! They don't highlight it as a tariff they offer!
I think that just goes to show more and more I need an EV! I have almost a years actual data from my solar system and five years from my friends so shall play around with this.
Ah, lovely data. Yeah, of course the other benefit of the EV is that you no longer need to spend money on petrol/diesel. We reckon we'll save about £50 a month on petrol by charging at home using overnight rate or solar.
Have you calculated the saving by charging the batteries from the grid in the off peak periods, and then using the stored energy in peak charge periods?
Yes, that's what I assume happens in this spreadsheet. It's not actually the optimum strategy for either of these tariffs however, since you'd be better off charging the battery with excess solar if you know the day to come is going to give you more solar than you can use, so this spreadsheet is a conservative estimate of the savings. This was the easiest way for me to calculate things on a daily basis, but to get a better value I'll need to break it down hourly and set up charging schedules for different times of the year etc. That's a work in progress.
@@TimAndKatsGreenWalk I have in the last week transferred to Octopus Intelligent, which gives me 6 hours of off peak electricity (23:30 to 05:30) and I have 3 x 8.2kWh GivEnergy batteries. The solar panels are set for 1) house use, 2) hot water, 3) battery, 4) vehicle charging, and finally 5) grid export. The batteries are set to accept solar generation, and then to download from the grid during the stated off peak period to 100%. So even in the depths of winter when the solar generation is minimal, I'm maximising the use of direct and stored off peak electricity.
@@johngriffin9720 good stuff.
Hi Tim
I have done some similar calculations and also found that Go/Intelligent was the better option until the 15p on export that you definitely can get on Cosy into account compared to the 4.1p on Go/Intelligent.
Yup, I added the option for different export tariffs to the spreadsheet last night as I hadn't realised you could get a higher rate on Cosy. That actually made Cosy very slightly cheaper for the Summer, ironically.
Yes we have a big solar array and no battery and also found that cosy would be better in the summer and Go/intelligent in the winter. Do you know how easy it is to switch between the two?
@@Willy_Eckerslyke I hear that it's pretty straightforward to switch tariffs with Octopus so maybe it's worth doing. The downside is that if the tariffs go up you might find your existing one is better. Good to have a spreadsheet to work it out!
@@TimAndKatsGreenWalk I'm not 100% sure, but I think that GO/Intelligent/Cosy/Flux aren't fixed any more i.e. they are variable tariffs based on the current Octopus Flexible rates???
@@Willy_Eckerslyke hmm, my Go rate is fixed for a year but perhaps the new one is variable. I'll investigate!
Really interesting Tim. I would be interested to know what payback difference it makes for the extra battery you added vs the original 9.5kW. I appreciate that the SS is making all sorts of assumptions but a comparison between the two battery sizes would be interesting. Like you I'm toying with adding more capacity to my original 9.5kW GivEnergy battery before it gets installed to take advantage of the 0% Vat.
£627 per year (on Go) with 13.5 kWh, £760 per year with 9 kWh (assuming 5% kept back from the 9.5 kWh battery). So the payback period becomes 13 years, rather than 12. The extra battery only saves about £130 per year, so arguably it's not worth getting if it costs more than about £1.5k. I think the cost of a 5.2 kWh battery is about £2k, so it's not likely to quite pay for itself, although adding that extra capacity might extend the life of the 9.5 kWh battery by a bit, so perhaps it's just about worthwhile? Also, Kat is happy about the fact that we can run the heating a bit more with the extra capacity, perhaps, so that's how I've sold her on the idea. Plus it gives you a bit more time with power in the event of a power-cut.
@@TimAndKatsGreenWalk Thanks Tim. Very interesting.
For you I can see why the extra battery capacity is a good thing for your A2A heat pump heating (& cooling) multi split system which you can keep running for longer without any grid power. Free cooling in the summer as well!
I still have gas CH for a while yet & no EV yet either so I think I'll wait until I add A2Air HP heating / hot water & add the extra battery at that point along with some more panels if I can. Once again thanks for the info.
@@colingoode3702 no problem, happy to help!
It pays off, sure, but I still think the monthly money in your pocket is the real value, assuming you don't have to take out a loan to afford it - which is why there really ought to be a national programme at least for local storage, as well as heat pumps and ideally solar for anywhere that can take it. But just about everywhere could have a battery of some sort.
The more local storage there is, the greener the grid because the more options there will be for flexible off/on peak peak periods.
If the whole grid was like that the monthly pocket benefits would likely reduce a bit but lordy the emission reductions on the national scale would be enormous. Could probably grow to 75% renewables just from reliably storing excess, never mind what happens if you add a solar roofing programme to add passive self generation.
I'm sure all that will come in time. The value for me is knowing I'm generating and using my own power. It just feels nice. I don't need the money in my pocket (I realise I'm lucky in that way, of course). Having that insurance against potential price rises is very handy though.
Fantastic, does the original link to the spready now contain the latest version?
No there's a new link in the description so check there for this version.
@@TimAndKatsGreenWalk Sorry, the description was minimised, should have realised. Thanks again.
@@oldgitflying no problem. I forgot to mention it in the video.
Thank you once again for the great information, question are you adding in the export potential of your production in the days you dont consume all the power ? On SEG its 15 per kWh. I cant remember but which video should I watch to see how much your total A2A solution was in cost ? I have someone coming round for a site visit next Thursday and keen to have a real life comparison especially due to the fact that I am going for the same type as you (Toshiba Haori) Ive looked at the rooms i want to cover and there will be a need for 8 units for 8 rooms that i want to heat with two of those rooms being fairly large 7.3m x 4.7m in size so im thinking that I should probably have to condensers on each end of the house with one condenser feeding one large room and 3 smaller rooms each so its evenly spread ? I would rather overspec that underspec so will be interested to see what the price would be but I cant remember how many you had installed and what the total cost was so i have at least a ball park figure for the install
Yes, the SEG is in there, although I think at the moment it's 4p/kWh (maybe 15 is a previous tariff, or am I out of date?). There is a cell you can enter that in, then any solar excess beyond what you use gets added as a credit to the total.
The video you're after is the tour of our A2A system, the first of the series. Take a look at the chapter markers on the description and you should be able to jump straight to it.
Ah, Octopus Outgoing is the 15p export rate but you can't have that with Go. With Go the export rate is 4.1p.
@@TimAndKatsGreenWalk Yes I get it due to being on COSY which im really finding good value compared to what i had previously. Dont have an EV so cant use the OCT GO tariffs. Getting the 15p for export would based on my last years export without getting paid anything due to no smart meter would be equal to £112 which is pretty good and at least pays for tthe standing charge and a little bit extra back. One more question after viewing the A2A video would you mind letting me know the size of your largest room the Kitchen/dining/snug room ? just trying to see if thats equal to one of my rooms so i can figure size of A2A to place in it. The pricing is really good and I'll need 2 large units 1 medium and 5 smaller units Im hoping it will all be under 15k
@@bobbazley5376 the big room is roughly 10m x 4m and has a 4.5 kW (cooling power) unit.
@@TimAndKatsGreenWalk I think you can still get the 15p rate with Cosy? Not sure how much difference that makes as your charge only seems to have one export value in M3. I have removed the car from your charge and adjusted solar to .9 (that matched my data). I get told GO cost is £565 a year. When I change export to 15p Cosy drops to £236 a year. It also shows me Cosy is cheaper in Dec & Jan two of the main months of wanting heating.
hi Tim - your solar system spec seems similar to mine (battery at least) I've a givenergy 5.0 hybrid invertor generation 1 and a 9.5 battery, and a ready to be installed 5.2 battery. Make sure to ask for the gen 2 invertor for your installation as the throughput to the battery is 1kw higher that gen1 (you probably know already). My installer is coming back in a few weeks to swap out my Gen1 for Gen2 and wire up the 5.3 battery. Also my array is 4kwp south east, 3kwp north west. What orientation/size are your panels? We still have gas for heating. Have an EV with Zappi and Eddi.. all good so far. Our tarrifs are different (Dublin). Curious as well if you are including conversion from AC to DC DC to AC losses in your calcs? cheers Mick
Yeah, we're getting a Gen 2 inverter, I made sure about that. The array will be 7.1 kWp split equally between due East and West. I'm not accounting for conversation losses in this spreadsheet because it's only a few percent and would be present regardless of the tariff so when comparing between tariffs it doesn't make much difference and the calculation was already getting quite complicated!
@@TimAndKatsGreenWalk people have told me the losses can be as high as 20 percent.. 10 percent each way
@@michaelmcgoldrick78 that sounds way too high to me. The specs suggest round trip efficiency closer to 95%.
@@michaelmcgoldrick78 I just looked it up. It sounds like the 20% losses figure is for lead acid batteries, while li-ion losses are closer to 5-8%.
@@michaelmcgoldrick78 www.cleanenergyreviews.info/blog/home-solar-battery-cost-guide#:~:text=Round%20Trip%20Efficiency,-5.&text=Generally%2C%20charge%2Fdischarge%20losses%20from,the%205%2D8%25%20range.
Does this take into account battery degradation? 12 years is beyond the lifecycle expected from GivEnergy but still very impressive to get it all "cost neutral"
No, it doesn't account for battery degradation, I'm sort of using this to work out what tariff would be best for the next year or so, so decided adding degradation would be unnecessary extra complexity. So that would affect the payback calc a bit. Although the uncertainty in future price changes would be a significantly larger source of error!
@@TimAndKatsGreenWalk Solar panel degradation over 25 years standard I see used by all as 15% so if you ignored replacing battery & use same as solar panel then you would inbuild a base degradation. As every year solar production is different & every month or day .... just in build some base reduction
the problem is you need a E V don't you to get on GO so the only option is Cosy or Flux
Not necessarily. They don't check everyone who applies for Go. We signed up last winter before we got an EV and it wasn't a problem. You might find you get lucky.
Does this allow for export prices?
Yes, there are cells to define the export prices for each tariff.
What can I say outstanding unless I am trying to sell you cosy can not wait for you to add flux and maybe x amount of kw for car charging 👍👍👍
Car charging is in there already (I showed that in the previous video so skipped over it for this one). Flux is gonna take a lot of work but I'll see what I can do!
@@TimAndKatsGreenWalk If flux turns out the same as cosy perhaps octopus will give you some hush hush £££
@@glyn1782 haha! We shall see.
@@glyn1782 haha! We shall see.
Great journey your on ... but as usual all about payback & cost on every channel I see which for base people mean little as suddenly it enters into our 2 Tesla cars use this & we have that & I am installing this new thing on trail. Not being negative just simple fact people choose there own energy provider & tariff that they can obtain & usually not linked to I have got every gadget under the sun simply to what they can afford. I have recently had solar installed & battery but also a voltage optimiser which converts mains from average 243V from mains to 220V as all appliances made have to work at 220V & this has made biggest saving everyday. Saving roughly 15% kWh coming in & also same coming from battery so double win.
Man, I can't win. I don't really care about the payback but if I don't mention it all I get are comments about "what's the payback?". It seems a lot of folks really care about that so I have to mention it, I'm afraid.
Nice;
Payoff - around 11:14 - That ~2k / year direct into batteries
The solar is a bonus in summer, but batteries appear to be a no-brainer to time shift Octopus go cheap rate to the day time. Well that was my gut feel anyway - to invest savings from the govt. electric subsidy + above thinking into 17kWh of battery storage.
To my mind the only issue to mitigate is longevity/stability of the battery solution so perhaps a phased purchase from different batches/vendors to even that out.
Personally I'm sticking with go anyway because:
1. EV - only at home overnight so needs those 4 off peak hours
2. Solar is west facing so only starting to see the sun now until Sept - and even then only from lunchtime
=> potentially means simple setup year round:
Fill the batteries overnight, they're approx @ 60% after breakfast/electric showers etc, ready for solar to top them up again in the afternoon.
If its a sunny day - the next overnight will need less topup - so sort of run the batteries full rather than leave space for potential sun tomorrow.
Yup, the batteries really are the key to getting the most out of both the solar and heating.