Octopus, did i imagine this?

[markc]

Just now, SteamyTea said:

That is the bit I have not found a good report on.

I don’t think there is much, if any good info. Even our suppliers give sketchy answers.

[Dreadnaught]

19 hours ago, JamesPa said:

I reckon that's unbeatable if you qualify, but also unsustainable for OVO

 

Interestingly Ovo is also offering a trial* of an add-on that incentives users to shift consumption away from the peak period (4pm to 7pm). It's a monthly refund for such usage shifting and can be taken along with the "heat pump add on".

 

I wonder if the "Heat Pump add on" might be eventually replaced by a new version that has the same low rate but excludes the peak period. A combination of the two. 

 

* called "Power Move" and it runs to at least December as an experiment.

[sharpener]

1 hour ago, SteamyTea said:

I still want to know about charging partly degraded batteries.

Say a 1 kWh battery has degraded to 0.8 kWh, I assume that it still takes just a bit more than 1 kWh to recharge it, say 1.05 kWh, but can only deliver 0.8 kWh.

Has anyone got any data on this, or willing to put an input and output meter on their system.

 

If I analyse the last 3 months of data which looks like this

 

 

and take account of various other reported data I get the result that 777 kWh went into the battery, 497 came out and 280 kWh is unaccounted for which is a gross efficiency of 64%.

 

If we assume the max usable capacity is 0.9 * 10.65 this is a actual output of 0.58 cycles per day. I would expect that to increase sharply now I am using all three charging periods though.

 

The figures assume the same state of charge at beginning and end of the period (max discrepancy 10kWh), and I can't tell from the data if this includes losses elsewhere in the system.

 

I did the same exercise a year ago over a 12 month period and IIRC the result was over 70% though I do not have the exact figure to hand. The old Victron forum has now been archived but I might be able to find it.

 

The battery reports a State of Health today of 95%; the last time I remember looking it was 98%. Two of the Pylontech 3.55kWh modules were installed May 2022 and the third that November.

 

Maybe this is circumstantial evidence that the efficiency is deteriorating along with the capacity but I would need more than the above to be convinced.

 

From lectures I have been to I am not sure that energy is wasted trying to change the state of sites in the matrix which are no longer receptive but I am not a battery chemist.

 

 

Edited October 24 by sharpener

[SteamyTea]

12 minutes ago, sharpener said:

280 kWh is unaccounted for

That is probably the invert/charge efficiency and some residual energy left in the battery.

 

Worth doing this eery month and see what the trend is.

I actually think that 70% (ish) is not too bad for a low entropy system.

[JamesPa]

Here is a crude attempt at tarrif comparison for some assumptions set out in rows 5-11.  The consumption figures are for me, but actually not atypical for UK houing

 

I have modelled tariffs stand alone, with a 9.5kWh battery and a 19kWh battery, for which local prices (fitted) are currently 5K and 7K respectively

 

The meat of it is to allocate the % consumption for each load type to the various timed tarrifs.  This is a bit of an informed guess in some instances so you should substitute your own numbers.  Where I am modelling with a 19kWh battery it is much less of a guess, as such a battery is large enough to cover a whole day (except car charging) for almost all of the year.  

 

My conclusion (which applies for me only)

• Dont bother with a battery, it doesn't pay, or doesnt pay by much (I might change my mind with the 'dont bother' bit if there is solid evidence of environmental benefit). 
• If I were to trust Ovo, the Ovo heat pump tarrif is the winner
• Otherwise get Agile or Intelligent Go or Cosy and just be faintly sensible about use during the peak charging periods, without busting a gut.
• Agile with a bit of intelligent manipulation of the heat pump to use the house as an energy score (as in what Homely, Havenwise, Adi and Passiv purport to do) looks like its well worth exploring and probably the best bet in the short to medium term

 

(There is also a plot of (UK) carbon intensity vs (Eastern England) Agile pricing, showing v poor correlation.  I need to do this again with East of England carbon intensity which might show better correlation, so at the the current time its a case absence of evidence for correlation carbon intensity<->pricing, which is evidence of absence.)

 

Criticism (preferably constructive) welcome.

 

 

 

Tarrif comparator.ods Tarrif comparator.xlsx

Edited October 24 by JamesPa

[sharpener]

1 hour ago, sharpener said:

I did the same exercise a year ago over a 12 month period and IIRC the result was over 70% though I do not have the exact figure to hand. The old Victron forum has now been archived but I might be able to find it.

 

It is here. Result for the whole of calendar 2023 was 69.5% so my recollection was wrong.

 

2 hours ago, SteamyTea said:

Worth doing this eery month and see what the trend is.

I actually think that 70% (ish) is not too bad for a low entropy system.

 

Doing the exercise for the past 12 months gives 66.3% which begins to look like a downward trend, but statistical variations can't be ruled out.

 

2 hours ago, SteamyTea said:

That is probably the invert/charge efficiency and some residual energy left in the battery.

 

Yes, in this analysis losses of all kinds are lumped together. But the inverter does get quite warm and the batteries show temps of up to 28C as well.

[PhilT]

4 hours ago, JamesPa said:

Here is a crude attempt at tarrif comparison for some assumptions set out in rows 5-11.  The consumption figures are for me, but actually not atypical for UK houing

 

I have modelled tariffs stand alone, with a 9.5kWh battery and a 19kWh battery, for which local prices (fitted) are currently 5K and 7K respectively

 

The meat of it is to allocate the % consumption for each load type to the various timed tarrifs.  This is a bit of an informed guess in some instances so you should substitute your own numbers.  Where I am modelling with a 19kWh battery it is much less of a guess, as such a battery is large enough to cover a whole day (except car charging) for almost all of the year.  

 

My conclusion (which applies for me only)

• Dont bother with a battery, it doesn't pay, or doesnt pay by much (I might change my mind with the 'dont bother' bit if there is solid evidence of environmental benefit). 
• If I were to trust Ovo, the Ovo heat pump tarrif is the winner
• Otherwise get Agile or Intelligent Go or Cosy and just be faintly sensible about use during the peak charging periods, without busting a gut.
• Agile with a bit of intelligent manipulation of the heat pump to use the house as an energy score (as in what Homely, Havenwise, Adi and Passiv purport to do) looks like its well worth exploring and probably the best bet in the short to medium term

 

(There is also a plot of (UK) carbon intensity vs (Eastern England) Agile pricing, showing v poor correlation.  I need to do this again with East of England carbon intensity which might show better correlation, so at the the current time its a case absence of evidence for correlation carbon intensity<->pricing, which is evidence of absence.)

 

Criticism (preferably constructive) welcome.

 

 

 

Tarrif comparator.ods 2.52 MB · 5 downloads Tarrif comparator.xlsx 2.73 MB · 7 downloads

Good effort. Cosy "normal" rate = 25.81

[JamesPa]

1 hour ago, PhilT said:

Good effort. Cosy "normal" rate = 25.81

Thanks, corrected.  With that change it works out almost identical to Intelligent Go and a bit cheaper than my model of Agile (which is deliberately a bit pessimistic).  Why do I suspect that all the variable price tariffs work out the very nearly the same for an average user unless you seriously 'game' them.  OvO heat pump still the cheapest by a fair margin, with the health warnings above.

[SteamyTea]

12 minutes ago, JamesPa said:

Why do I suspect that all the variable price tariffs work out the very nearly the same for an average user

Because they use the same data set.

 

https://bmrs.elexon.co.uk/market-index-prices

[sharpener]

21 minutes ago, JamesPa said:

With that change it works out almost identical to Intelligent Go and a bit cheaper than my model of Agile (which is deliberately a bit pessimistic).

 

Thanks @JamesPa, interesting conclusion. Haven't got access to Excel right now, could you perhaps (i) print the results to pdf or (ii) summarise why it is there is little difference between Intelligent Go and Cosy - there are many ppl on Vaillant FB who are adamant that IG is much better. In the SW I pay 24.71, presumably regional differences in rates don't affect the conclusion, I imagine it balances out as both reflect the costs of distribution.

 

At least that was the rationale in the OFGEM review a while back which said they are "fair", though personally I think they are a massive confusion for marginal benefit and ought to be levelled out.

 

BTW depressing anti-smart-meter program on Ch 5 as I write, presenter talking about "kettle takes 3 kW per hour" etc etc and then has brass neck to say ppl find kWhs "confusing" - well they certainly are to her!

 

 

Edited October 24 by sharpener

[SteamyTea]

2 minutes ago, sharpener said:

Haven't got access to Excel

It is 40 years old now.

I have swapped it for a younger model.

[G and J]

2 hours ago, SteamyTea said:

It is 40 years old now.

I have swapped it for a younger model.

Hey! I started on SuperCalc which I believe was a forerunner of Excel. 
 

Boy, am I feeling old. 

[SteamyTea]

4 hours ago, G and J said:

SuperCalc

VisiCalc on a PET for me.

[PhilT]

4 hours ago, SteamyTea said:

VisiCalc on a PET for me.

Ah, VisiCalc, the first commercial spreadsheet. I used it on an Apple IIe. Cue jokes about 5" floppy drives.

[JamesPa]

12 hours ago, sharpener said:

Thanks @JamesPa, interesting conclusion. Haven't got access to Excel right now, could you perhaps (i) print the results to pdf or (ii) summarise why it is there is little difference between Intelligent Go and Cosy - there are many ppl on Vaillant FB who are adamant that IG is much better. In the SW I pay 24.71, presumably regional differences in rates don't affect the conclusion, I imagine it balances out as both reflect the costs of distribution.

Attached a print out

 

In response to your question, it really depends on the assumptions you make about when you operate the high-draw items (which is adjustable in the spreadsheet).  In all my modelling I assumed that no account is taken of the tarrif when deciding to operate equipment, with the exception of car charging where I make more generous assumptions.  I did this because it is the 'lazy' option which I fear many, including me, will default to, and also because it paints batteries in a 'good' light (my initial motivation for the exercise was to prove, or otherwise, that batteries don't make financial sense, so by painting them in a 'good' light any conclusion that they don't make financial sense is relatively robust).  Cosy also might have an un-modelled advantage in the shoulder season when perhaps your heat pump struggles not to cycle.  In this case operating the heat pump only during the cheap periods will likely reduce the electricity cost without materially compromising efficiency (because the heat pump was destined to cycle anyway).  Interestingly Cosy Mk2 (with the three low price periods) is now entering its first winter.

 

With any ToU tarrif, and a sufficiently capable heat pump controller, there is the opportunity to 'pre-load' the house, warming it up above the desired temperature before a high tarrif period kicks in.  Thats exactly what homely and the like do.  Cosy may be better suited to this than Go because the cheap periods are better distributed, but I didn't build this into my modelling.  TBH I think Agile is even better suited to this behaviour than cosy because there is much more low price time even better distributed still.  Although there is some uncertainty when the low price time will occur, in practice its pretty predictable.  Of course Homely and the like have the advantage of looking ahead a day so they know what the future price and temperature is, and thus can be more intelligent about this optimisation than any timed controller can.

 

The percentages of each load class assigned to the different prices within any one tarrif are adjustable, so if anyone wants to make radically different assumptions to see how it changes the picture they can.  Even if you dont intend to buy a battery its quite interesting to look at the 19kW battery column where I essentially assume all, or nearly all, the electricity is at the lowest price.  The trick would be to achieve this, or something close, without the upfront cost of a battery.  With Agile, intelligent control and a house with a reasonably high heat capacity I reckon that may be close to do-able for the heat pump which is the dominant load.  Homely, Havenwise, Adia, PassivUK (the four I know of, there may be more) are, I think, targeting more or less exactly that.  In time I imagine energy suppliers will offer remote heat pump control with some sort of guarantee on minimum and maximum house temperature, so they can load balance.  The technology that Havenwise is developing is particularly well suited to this case, as it doesn't require any hardware, just an internet connection.

Tarrif comparator.pdf

Edited October 25 by JamesPa

[PhilT]

8 minutes ago, JamesPa said:

Tarrif comparator.pdf 195.93 kB · 0 downloads

One other thing I just noticed is that Cosy cheap rate hours I think are 8, not 7?

 

Definitely useful as a directional steer, obviously you can debate the assumptions till the cows come home but that's where the "modelling" bit comes in based on your own particular circumstances.

 

O

[JamesPa]

2 minutes ago, PhilT said:

One other thing I just noticed is that Cosy cheap rate hours I think are 8, not 7?

 

Thanks, model corrected and attached in various formats.

 

4 minutes ago, PhilT said:

Definitely useful as a directional steer, obviously you can debate the assumptions till the cows come home but that's where the "modelling" bit comes in based on your own particular circumstances.

Precisely.  As I say above I made somewhat lazy assumptions about how ToU tarrifs would, in practice, be used but others may be more aggressive. 

 

The interesting thing, for me, it to 'play around' with the assumptions to do a bit of sensitivity testing.  Just doing this can give a very good indication what choice to make and whether the choice really matters given the uncertainties.  For example its clear to me from this analysis and with my assumptions that I would be mad to stay on a fixed tarrif, but the choice between Agile, Cosy and Go is 'in the noise' of the precise assumptions, so unless I tie those down and follow through on them in practice its not worth sweating over which.  This allows me to rule out Go because, although I do have an EV, I don't need a car charger, which is mandatory for Go.  Likewise the battery case simply isn't made for me, so I can set that aside until battery prices fall by 30% or energy prices rise similarly.  Models, and their assumptions, only have to be good enough to allow informed decisions to be made which often does not require anything particularly precise.

Tarrif comparator.ods Tarrif comparator.pdf Tarrif comparator.xlsx

[PhilT]

2 hours ago, JamesPa said:

 

Cosy 2 is a no brainer for me, at least for the room heating months anyway. I used Cosy 1 when it was launched but that extra 22:00-00:00 low rate makes a useful difference. Re the spreadsheet I reckon I will still export around 50% of my solar, without the battery, at 15p/kWh, but obviously most of that will be in the summer months.

[JamesPa]

2 minutes ago, PhilT said:

Re the spreadsheet I reckon I will still export around 50% of my solar, without the battery, at 15p/kWh, but obviously most of that will be in the summer months.

Yes me too (although it should be getting less with the EV and a bit of automation I have set up.  The spreadsheet assumes 50% export in all scenarios, thats the allocation to sub-tarrif D.   I dont think this particular assumption makes that much difference (for a 4kWp system) because most of the tariffs have a low rate around 15p or below.  If the low rate is below you would ideally export excess solar anyway.  If you have a much larger system then it could make quite a difference indeed.

[JoeBano]

With octopus agile you can use the automation app IFTTT. I was using this system last year, it would find the cheap periods with octopus agile and tell my hestmiser stats to turn up heating up. Once I knew the rough average cheap times I told my heat pump (grant aerona3) to go into low tariff mode and boost my flow temperatures for that period resulting into a slightly hotter house for the 4-7pm expensive period. My heat pump never really came back on till the 10pm. 

[sharpener]

4 hours ago, JamesPa said:

Thanks, model corrected and attached in various formats.

 

Thanks for the narrative explanation and the pdf @JamesPa.

 

I see it still has Cosy cheap rate for 8 hrs in places and 7 hrs in at least one.

You are obviously aware of "Cosy 2" intr. earlier this year but you don't seem to have modelled it (I am paying this in the SW).

 

 

As you say, the assumption that the high energy items' consumption is spread evenly is quite pessimistic, but doesn't affect the inter-tariff comparison much, as the opportunities to timeshift say a dishwasher are adequate on all of them.

 

BTW I have done some more analysis of my battery losses and will link to a writeup on the Victron site in due course. It re-inforces my notion that their Dynamic ESS is not doing a very good job bc it now seems to be costing me 18p gross/unit to charge the battery at night to achieve 15/unit extra PV export during the day.

 

4 hours ago, JamesPa said:

This allows me to rule out Go because, although I do have an EV, I don't need a car charger, which is mandatory for Go. 

 

IIRC not if you have an accredited car (see checker on Octopus website), maybe you don't?

 

Havenwise looks interesting, particularly as Homely didn't have integration with Vaillant when I last looked. But as debated on RHH if it just emulates a good ToU and WC setup it may not help us much.

 

[JamesPa]

31 minutes ago, sharpener said:

I see it still has Cosy cheap rate for 8 hrs in places and 7 hrs in at least one.

 

 

True, I corrected the hours in the base model but not the cosy + battery models.  It makes no difference and none of the calculations other than in the base model rely on this.

 

31 minutes ago, sharpener said:

You are obviously aware of "Cosy 2" intr. earlier this year but you don't seem to have modelled it (I am paying this in the SW).

 

 

I think I have,, I have three rates 25.81, 12.65 and 37.42 (which are the three cosy rates in Eastern England.  One of the 'Battery' titles is wrong, it should say Go not Cosy.

 

31 minutes ago, sharpener said:

As you say, the assumption that the high energy items' consumption is spread evenly is quite pessimistic, but doesn't affect the inter-tariff comparison much, as the opportunities to timeshift say a dishwasher are adequate on all of them.

I thought about this a bit.  You can move the dishwasher but are unlikely to change when you cook or make tea (not that making tea is a significant consumer).  So I reckoned you inevitably use some of the high energy load during peak hours

 

31 minutes ago, sharpener said:

IIRC not if you have an accredited car (see checker on Octopus website), maybe you don't?

 

My car (e-niro) is suitable but as I don't have any charger (I just use a 13A socket) the combo is not.  I had thought Octopus relied on the charger to do the on/off bit but checking back I see that I am wrong there are cars that will work without an accredited charger; I therefore presume that either the car or the charger must be accredited.

 

31 minutes ago, sharpener said:

Havenwise looks interesting, particularly as Homely didn't have integration with Vaillant when I last looked. But as debated on RHH if it just emulates a good ToU and WC setup it may not help us much

I spoke with the Havenwise people yesterday.  They integrate with Vaillant, Samsung, Mitsubishi and Daikin.  Currently they charge £50pa for the service which targets cost optimisation with a ToU tarrif at the 'expense' of allowing the house to get up to 2C warmer than the target (which they regard as a minimum). 

 

I'm thinking that this is pretty cheap (I was expecting £10 per month which seems to be a standard 'service' charge) but this will be their first 'commercial' winter so I guess it has to be.  I'm seriously tempted (but need to get the heat pump in first!).  I do wonder whether their long term goal is to be bought out by Octopus and integrated into Kraken.  

Edited October 25 by JamesPa

[sharpener]

11 minutes ago, JamesPa said:

I think I have,, I have three rates 25.81, 12.65 and 37.42 (which are the three cosy rates in Eastern England.  One of the 'Battery' titles is wrong, it should say Go not Cosy.

 

Yes but the times are 13hrs, 8 and 3

 

13 minutes ago, JamesPa said:

My car (e-niro) is suitable but as I don't have any charger (I just use a 13A socket) the combo is not.  I had thought Octopus relied on the charger to do the on/off bit but checking back I see that I am wrong there are cars that will work without an accredited charger; I therefore presume that either the car or the charger must be accredited.

 

Correct. But your e-niro is not accredited so it would need an accredited charger not the 13A socket. OTOH with an accredited charger I think (nearly) all EVs are suitable.

 

15 minutes ago, JamesPa said:

I do wonder whether their long term goal is to be bought out by Octopus and integrated into Kraken.  

 

Forlorn hope I would guess. Since Octopus bought out RED 2 yrs ago and are already producing their own (hideous) 6kW unit (having binned most of RED's innovative ideas) I would guess they are a long way down this integration path. But it does happen, a Cambridge startup I knew was bought out and became BG's home automation offering.

 

When I have a spare moment I will contact them out of interest to see what I can glean.

[JamesPa]

2 minutes ago, sharpener said:

Yes but the times are 13hrs, 8 and 3

er Im now confused, isnt that what I have (in the first model, which is the only one that uses these numbers) or am I going mad?

 

[JamesPa]

6 minutes ago, sharpener said:

When I have a spare moment I will contact them out of interest to see what I can glean.

I expect you will be offered a half hour slot with Henri, which is where I got my info from.  They are taking customers now.

Edited October 25 by JamesPa