Predbat - I have questions (lots!)

So I have had Predbat running for a couple of days now, it is very cool! However, I have some questions that I am hoping someone with experience of using it can help with.

Is it possible to look back at previous days' graphs and compare them to todays? I would also like a chart that tracks the overall cost per year. This seems like something that shouldn’t be that hard but I don’t have the knowledge to make it work. I figure taking the cost so far today's number at 23:59 and adding it on to yesterdays to create a running total that is added to would give this. But then it needs to track the numbers so it can stop at 365 which is where I run out of knowledge. I also don’t know how you would store that running total, I guess you would create some kind of helper? Does anyone know how to do this? I feel like this could be a cool dial card in HA.

How accurate is the cost prediction? The profit it seems to be reporting seems really quite high, I have only had this running for 2 days but both of those (reasonably cloudy) days predbat has forecast that I will make around around a £3-4 profit. Even factoring in seasonal variations this seems to equate to at the very least free electricity and possibly even getting paid by Octopus! That seems too good to be true so what are peoples real world experiences? Do you actually make money from this setup?

This also raises certain ethical questions for me, while this is making me money, charging the battery from the grid when it is very cheap (as it has been recently, often below 1p / unit) and then selling back to the grid for 15p / unit is a fantastic deal for me. However this does seem rather wasteful of energy and somewhat against the nice warm snuggly feeling of using green energy. Is this something others have considered and what conclusions have you come to?

Reading up on factoring in the cost of the battery cycles - side note, I am yet to find that setting and clicking the expert more button didn’t seem to do anything to my card, how do I do that? Is there a way to set it to only cycle that battery within a range? I have an electric bike and did a lot of reading on battery life and cycles and I read that you can effectively cheat extra cycles out of a battery by only using the middle bit. I can’t remember the exact numbers off the top of my head but it’s something like going from 40% - 80% charged 4 times counts as a single full cycle not 160% of a cycle as you have actually used and therefore makes your battery last longer, definitely worth doing when they are around £4k a pop.

Sandy To track your daily/weekly/yearly costs, you can feed your cost sensor into a utility meter helper in HA. You can setup as many as you want, so you can have one for weekly cost, another for monthly, another for yearly etc. Just set the reset cycle of each one appropriately ... you can read about them here https:// www.home-assistant.io/integrations/utility_meter/

This also raises certain ethical questions for me, while this is making me money, charging the battery from the grid when it is very cheap (as it has been recently, often below 1p / unit) and then selling back to the grid for 15p / unit is a fantastic deal for me. However this does seem rather wasteful of energy and somewhat against the nice warm snuggly feeling of using green energy. Is this something others have considered and what conclusions have you come to?

So, you could argue, that you are being super green, you feeding back into the grid during the day is better for everyone?

paddyb Thank you, this sounds like exactly what I'm after :-)

shawry I agree but it doesn't do just that. Both last night and tonight it is planning to do a charge / discharge cycle overnight because the cost of importing is less than the cost of exporting and therefore will make me money. Obviously I like making money but I'm not sure how I feel about doing that by taking the cheap power, wasting some through the inefficiency in the battery and inverter and then pushing it back to the grid simply because there is a profit gain. The reason it is so cheap must be because there is an abundance of green energy being produced (it's windy / sunny) and therefore it would otherwise be wasted but taking it and selling it back when it's not needed feels like it is simply gaming the system. It really feels wasteful which is totally opposite to one of the primary reasons I got the system installed in the first place

I fell like surely Octopus would shut this down in time if enough people do it. They are still a profit based company.

There is also the consideration of the cost to the battery and the shorter life span that creates. Aside from the monetary cost of replacing the battery (which is significant) the resource cost of the replacement battery - which is now in need of recycling - is huge. Hence, in part, my question about charge cycles.

This is an incomplete thought at present and I'm working though my reasoning. I'm blown away by how cool this thing is, it's an incredibly good tool but this bit makes me feel mildly uncomfortable right now so I am keen to hear other peoples opinions on this.

paddyb It seems the cost today value is not a unique entity so can't just be plugged into a utility meter. There is probably a way to create a sensor that does output that number but I don't currently know what that is. Thanks for the point though, this is helpful

paddyb Sandy To track your daily/weekly/yearly costs, you can feed your cost sensor into a utility meter helper in HA. You can setup as many as you want, so you can have one for weekly cost, another for monthly, another for yearly etc. Just set the reset cycle of each one appropriately ... you can read about them here https:// www.home-assistant.io/integrations/utility_meter/

You can do it with utility meters but I’d argue the better solution is to feed the information in to the energy dashboad in HA that will do it all for you. Have a look at Speak to the Geek video on energy dashboard and givtcp

You can then track solar, house load, generation and individual devices over time.

The question of whether you want to take advantage of the import/export rate disparity at the moment is a personal one. Remember Octopus are in the money making business and if they weren’t making money off you they wouldn’t be offering the tariffs they do and even highlighting the use of your battery to discharge previously stored electricity.
Its not often we get rates as low as this on agile so its not like its an every day risk for them.

If you have decent enough solar production then yes you should be in profit in the summer. I’m in profit so far every day in April, but with a heat pump I use loads in the winter, so overall will end up at about zero for the year.

Sandy s there a way to set it to only cycle that battery within a range?
The givenergy batteries already do this. The 9.5kW battery for example is actually 13,5kW internally but we only get to access the middle bit of it.

All bar the very old batteries have unlimited cycle warranties on them, so use it, you’ve paid for it.

If you want to reduce the use of your battery, set a metric_cycle_cost (cost of charging/discharging the batttery), and/ or a min_soc_keep (amount of soc to keep in the battery). But basically you’ve paid for it, might as well use it than not use it!

geoffreycoan Thank you, I have only posted a couple of threads on this forum but each time you have come back with helpful, knowledgeable and insightful comments.

You can do it with utility meters but I’d argue the better solution is to feed the information in to the energy dashboad in HA that will do it all for you. Have a look at Speak to the Geek video on energy dashboard and givtcp

I actually set this up the other day using the GivTCP sensors following the exact video I think you are referring to but I hadn't realised it was already tracking total cost over time for me. I already have exactly what I was looking for!

The question of whether you want to take advantage of the import/export rate disparity at the moment is a personal one. Remember Octopus are in the money making business and if they weren’t making money off you they wouldn’t be offering the tariffs they do and even highlighting the use of your battery to discharge previously stored electricity.
Its not often we get rates as low as this on agile so its not like its an every day risk for them.

Good points. I haven't had my system long enough to get a decent idea of cost over time and have only just started paying close attention to the agile pricing.

I’m in profit so far every day in April, but with a heat pump I use loads in the winter, so overall will end up at about zero for the year.

Net zero cost for all energy in your home is fantastic. I don't have a heat pump (yet) so that hopefully means I should work out slightly in profit for the year.

All bar the very old batteries have unlimited cycle warranties on them, so use it, you’ve paid for it.

This is excellent news

Sandy
A (exceedingly rare) chance to clarify something that Geoffrey said: you may want to check out a recent summary of the Givenergy warranty. There are limits if you indulge in behaviour that could be considered non-vanilla (top of page 3). Note also that they warrant 70% (point 3).

https://givenergy.co.uk/wp-content/uploads/Product-Warranty-13.02.2024.pdf

Sandy geoffreycoan Thank you, I have only posted a couple of threads on this forum but each time you have come back with helpful, knowledgeable and insightful comments.

thanks for the kind comments. That was a rather quick reply bashed in before I went to bed, so lucky it still made sense !

You should end up with something like this in the energy dashboard. If you are on agile there are some special “tricks” to configure the dashboard to get it to appear properly, follow the instructions on the bottlecap dave integration
I have multiple arrays, batteries and inverters, plus there is some multi-tariff legacy stuff from when I was on Flux that makes it look more complex, but shows my results so far today