Posted by: @sheriff-fatman

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Posted by: @jamespa

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Posted by: @sheriff-fatman

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Are you restricting your choice to specific high-cost batteries in your calculations, or is there some specific non-obvious constraining factor being reflected, as it's the only way that I can think that you'd conclude that the payback wouldn't work?

I dont know TBH.  Quotes for installed batteries seem very similar, a bit more than: 2.5K=5kWh, 5k=10kWh, 8-9K=20kWh.  I am including cost of capital.  I am assuming 4% interest but also accounting for tax on the interest (which is favour of the investment).

If I stretch things I can just about get payback = 8 years, mostly its 10 years.  This is based on EON Next Drive (2025 edition) which has a large differential between cheap rate and nighttime rate (6.7p vs 25.4p)  Roughly speaking I do 50% of my import at night rate and 50% at day rate.   

Does that answer your question.  Im trying to make it work, I'm not trying to find reasons not to do it!

So, assuming any technical issues could be overcome, if you factored in a 16kWh battery cost at £2,000 or a 32kWh battery at £3,400 and added on a cost to install (they've been described as 'plug and play', but this is generally referring to swapping out Sunsynk batteries for these, so that might be an oversimplification), does that price level make a big enough difference in your overall calculations?

I'm an accountant, so am very familiar with opportunity cost type calculations, and DCF analysis, which I assume yours are if you're figuring in interest lost and tax on interest saved, but the underlying price of the batteries appears to be the big constraint in your calculation.  The Fogstar ones seem to be generally acknowledged as being the best value cost/kWh of reliable storage options currently available so if the calculation doesn't work at those prices, then I guess it won't work at all.

Not necessarily. Some more expensive batteries (e.g, GivEnergy, Tesla) also give access to more lucrative tariffs (Intelligent Octopus Flux), so one could base a strategy around the purchase of the cheapest battery that would give access to those more lucrative tariffs (see my post above) which may change the economics (or not).

I think it also depends on how you treat at the purchase. Considering a purchase of a "solar + battery system" is very different from considering adding a battery to an existing solar system where the initial gains (low hanging fruit) of solar are already baked in and the expensive battery then offers a diminishing return.

@old_scientist Interesting point, but I suspect that's not a typical usage case for most people.

I'm using Intelligent Octopus Go.  I've looked previously at the Flux options and, on each occasion, have concluded that they're not as cost effective as the EV rate in my case, particularly when I factor in the car charging requirements for 2 vehicles.

Based on the difference in pure battery cost I doubt that tariff savings on the more lucrative rates would offset the capital cost difference over a reasonable payback period, unless the solar/export capability was on a much bigger scale than a typical system.  I don't think my 6.3kWp system with 5kW inverter would have sufficient capacity to 'trade' a saving on that sort of scale with our typical usage patterns.

Posted by: @old_scientist

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I think it also depends on how you treat at the purchase. Considering a purchase of a "solar + battery system" is very different from considering adding a battery to an existing solar system where the initial gains (low hanging fruit) of solar are already baked in and the expensive battery then offers a diminishing return.

I think that's the essence of my problem.  I bought into solar in 2011 so the battery (with an additional inverter) needs a standalone business case (because I cant see it has a strong environmental case given the poor correlation of electricity price with greenness so far as I have established to date).  Furthermore the battery inverter and installation thereof has to be justified against the battery alone, rather than being split between the two.  

When my solar inverter fails it may be a different calculation.  Oddly enough a battery installer told me the other day that the one I have is proving to be one of the mist long lasting models, so that may not be for some time!

@jamespa I’ve noticed a common factor in many of these posts and that is ‘the case for a battery doesn’t add up’ often relates to the TOU (EV) tariff; by this I mean if one is on a ~7 pence per kWh rate, then the case is very different to those who are paying ~ 14 pence per kWh or more. It suggests to me that having that EV battery facility - though it may not be used for powering anything other than the vehicle is a passport to a totally different scenario. Regards, Toodles.

Posted by: @toodles

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@jamespa I’ve noticed a common factor in many of these posts and that is ‘the case for a battery doesn’t add up’ often relates to the TOU (EV) tariff; by this I mean if one is on a ~7 pence per kWh rate, then the case is very different to those who are paying ~ 14 pence per kWh or more. It suggests to me that having that EV battery facility - though it may not be used for powering anything other than the vehicle is a passport to a totally different scenario. Regards, Toodles.

You are absolutely right. 

I think another common factor may be whether the battery is installed at the same time as solar or is an add on to existing solar.  The inverter plus its installation accounts for perhaps £1.75K out of the total cost and most inverters these days can accommodate both battery and solar inputs.  So if you only have to do it once, because you are doing solar and battery simultaneously then thats a lot off the cost.  If you are adding it to existing solar then you still need to spend the full 1.75K but it all has to be 'justified' against the battery.

Posted by: @papahuhu

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@batpred Fair enough, if the usage of these materials is solely coupled to financial gain then that is at least honest. I designate myself to the camp of absence of empathy and callousness to the harm to others I’m causing, hard to define it as anything other than textbook psychopathy.

😆

I never saw it as simple as that.  Just stick to "gas and the proceeds of selling it being used to fight a war"... 

Otherwise, how is a common human supposed to decide?  

My decision on the inverter and battery was complicated enough by considering where to install the thing, what software I was planning to use, the regs and scams that could become a minefield, etc...  

Now that the system is ready, letting it rest would be a waste, I think. I do not have a masochist trait, so will not start evaluating what is the time that would really contribute to less emissions.

My HA system has been down for a few days due to running out of space and I never managed to get the module that would supposedly calculate the greenest time to export working. 😑  

Solis AI has a tick box that works on price...  😉   

Posted by: @toodles

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... though it may not be used for powering anything other than the vehicle is a passport ...

How is a human supposed to understand the integrations that octopus came up with to make sure it only charges the car? To get them working you may need a few specialists... 😉 didn't work so far with me.   

And I really enjoy that passport concept.. Once your company paid you for the passport for business travel, no point to get another for leisure, right? 🍾 🥂 

Posted by: @batpred

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How is a human supposed to understand the integrations that octopus came up with to make sure it only charges the car? To get them working you may need a few specialists... didn't work so far with me.

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The cynical answer is that perhaps they don't want us mere mortals understanding.

The more charitable answer is that Octopus are constantly experimenting with tariffs and so they'll work on the ease of understanding once the proof of concept is shown.

My natural mistrust of corporate morality would normally have me leaning to the first answer, but the way I've seen Octopus do business thus far has me more inclined to accept the latter - or at least believe it could be true.

@majordennisbloodnok 

My experience of them for the last 6 years has been overwhelmingly positive, perhaps even moving towards relative altruism to their customers. They have to make a profit to survive, however that profit has never been excessive nor have leadership salaries been excessive in comparison to their peers. The relatively small profits appear to be invested back in the business but pension funds own a small part of the business so they must be providing a return.
I seem to remember Greg Jackson taking minimum wage for the years of the energy crisis and no silly bonuses, but being a private business there isn’t full transparency. On the face of it a good egg, probably next week we will find he was best mates with Epstein and my faith in humanity misplaced once again. 

Posted by: @majordennisbloodnok

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Posted by: @batpred

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How is a human supposed to understand the integrations that octopus came up with to make sure it only charges the car? To get them working you may need a few specialists... didn't work so far with me.

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The cynical answer is that perhaps they don't want us mere mortals understanding.

My gut feeling is similar, I think Octopus means well. 🙂 

So I can see someone dreamt a way to technically make sure the tariff is only being used for EV charging. But as soon as they hit the dreaded EV charger (that is yet to respond to my latest problems), they admitted that they only need to interface with the vehicle! 😆

This implies the current goal is more about monitoring charging... eventually they could bring a new tariff (with software that would do the same that the BMW app can do but also drive a dumb socket). Surely not this "smart" EV charger. I think they already sell EV chargers. They are not ones that would waste cycles trying to get around security of ISO designed APIs... 

They seem to have a good reference model of what renewable equipment could be in a typical home and want to map it. But with DNOs not mapping it as well, etc it is a data quality challenge. Octopus are also flexible to accommodate home grown solutions and they also reward "innovators".  😉 

Posted by: @papahuhu

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My experience of them for the last 6 years has been overwhelmingly positive, perhaps even moving towards relative altruism to their customers. 

Same here.

The pace of change of their apps is absolutely mind boggling.. And very rarely have I seen any glitch. Their support understands niggles quickly and more importantly owns up to fixing them. 

Posted by: @batpred

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Posted by: @majordennisbloodnok

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Posted by: @batpred

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How is a human supposed to understand the integrations that octopus came up with to make sure it only charges the car? To get them working you may need a few specialists... didn't work so far with me.

...

The cynical answer is that perhaps they don't want us mere mortals understanding.

My gut feeling is similar, I think Octopus means well. 🙂 

So I can see someone dreamt a way to technically make sure the tariff is only being used for EV charging. But as soon as they hit the dreaded EV charger (that is yet to respond to my latest problems), they admitted that they only need to interface with the vehicle! 😆

This implies the current goal is more about monitoring charging... eventually they could bring a new tariff (with software that would do the same that the BMW app can do but also drive a dumb socket). Surely not this "smart" EV charger. I think they already sell EV chargers. They are not ones that would waste cycles trying to get around security of ISO designed APIs... 

They seem to have a good reference model of what renewable equipment could be in a typical home and want to map it. But with DNOs not mapping it as well, etc it is a data quality challenge. Octopus are also flexible to accommodate home grown solutions and they also reward "innovators".  😉 

 

It might be unintentional, @batpred, but that's a significant misquoting of my previous post.

I gave two possible interpretations - one cynical and one charitable - and concluded I'm more inclined to the charitable one. However, in your quoting you've only included the interpretation that I discounted.

For clarity, if we were talking about pretty much any other supplier I'd be inclined to think the worst of them. However, so far Octopus have appeared to consistently conduct themselves well enough that my instinct is to assume they're trying to do the right thing.