How to getthe best out of Octopus Flux

Interested to see what you spit out of my spreadsheet @Ron-ski :)

I'm still interested in Flux but I will wait a bit more, generation figures still a little weak, and the next 7 days or so don't look great.

Main benefit of Flux is the lack of needing to babysit it, and is certainly one reason I'd really consider it a good competitor.

My calcs also show that based on my figures I can get comparative performance over winter from Eco-7 if I'm careful.
 
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I've had an email from Octopus, they just needed to know whether I wanted to move just FITS export, or FITS export and generation to them, hopefully I'll move over soon. On another forum it seems they've had so many applications there's quite a back log, which I guess why people haven't had emails yet who've registered their interest.

@HungryHippos I'll take a look at the spread sheet tonight.
 
HungryHippos said:
Interested to see what you spit out of my spreadsheet @Ron-ski :)
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I adjusted the prices, set the battery to 28kWh, and the charge / discharge rate to 7.5 and got the following. It makes no difference increasing battery size over 28kWh as I can't charge or discharge quick enough.

So if I'm reading that correctly that's an estimated cost of £1.43 a day, without taking into account excess solar that is exported/used. Changing the charge / discharge rate to 8kw means a cost of £1.14

I think there may be a slight bug in the spreadsheet, I come out of the three hour peak period having exported 3 * 7.5 = 22.5kWh, which leaves 5.5kWh, but it suddenly disappears, as there's no schedule it should decrease by 0.7 per hour until its gone, so should last through to the charging period.

Also got a negative value at I22 and K22, not sure if that is correct.

Flux-Spreadsheet.jpg
 
Ron-ski said:
I adjusted the prices, set the battery to 28kWh, and the charge / discharge rate to 7.5 and got the following. It makes no difference increasing battery size over 28kWh as I can't charge or discharge quick enough.

So if I'm reading that correctly that's an estimated cost of £1.43 a day, without taking into account excess solar that is exported/used. Changing the charge / discharge rate to 8kw means a cost of £1.14

I think there may be a slight bug in the spreadsheet, I come out of the three hour peak period having exported 3 * 7.5 = 22.5kWh, which leaves 5.5kWh, but it suddenly disappears, as there's no schedule it should decrease by 0.7 per hour until its gone, so should last through to the charging period.

Also got a negative value at I22 and K22, not sure if that is correct.
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Ah yeah I see the issue, it's because the cells from G22 to the end need to account for slippage against the hourly consumption instead of the battery limit.

Change both the $B$2 references in G22 to $B$3 then drag it to down to the end, battery should drain and it will fix the other issues you noted as well.

Export is based on max rate but also negates house consumption, which is why you can import at the max rate for grid powering home + charging the batteries, but dumping battery out the feed will likely go to house first so at top speed some will be skimmed off the outgoing for home consumption.

This is kind of taking bad scenarios into account again though, no solar, using from grid in the day etc. I think on most days all those middle 0.7's would either be negated, or would be less.

Could possibly skip the charge after 05:00 as well, just hold the min SOC % at around 80-85% and let solar top up the rest as needed, would cause the battery to flip flop up and down a bit though.

In the example with corrections, in 3 hours from 02:00 - 05:00 24.60 kWh is imported at a cost of £5.05.

Later in the day 20.40 kWh get exported, which generates £7.91 worth of export cash.
 
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So yesterday i exported 10.18kwhs @ 22.37p = £2.28
0.120kwhs @ 36.55= 4.3p

and i imported = 0.227kwhs @ 20.38p = 4.6p
= 0.320kwhs @ 47.55 = 15.2p
= 2.313kwhs @ 33.97 = 78.13p

So i made £2.323 - ( 4.6+15.2+78.13+47.52) = 88.97p


and yes i only used 2.9kwhs from the grid yesterday, super low importer, good exporter
 
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Well, seems my switchover to Flux has now completed for both import and export, annoyingly seemed to complete on midnight on Tuesday after Tuesday was my best export and generation day of the year so far, so would have been nice to catch that, but oh well.

One slight annoyance, I spent ages writing an app to control my battery, charge overnight based on the forecast etc. and now a lot of that seems largely pointless as seems like it is probably going to be best to just charge as much as possible overnight as the minimum daytime export rate is better than the overnight price.

I think the one exception might be on very good days where my generation could exceed my export limit (I believe I am limited as only have G99, but a 5.4KW array and 5KW inverter), so on days like that it would likely be worth diverting excess generation to the battery (so therefore not fully charging overnight), rather than it just being wasted, though TBH that's not going to be a huge amount of power after the house draw.

Will maybe just repurpose the app to help keep track of my daily expenditure and earnings, as doing that on a spreadsheet is getting increasingly complex!
 
Ron-ski said:
@Tavis75 you should be able to check in your documents if you have an export limit. Its also a limit on maximum export power, so kW, not kWh, so if the limit was 5kW you could export at 5kW all day long.
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Yes, I understand the limit is KW not KWh, but if I was in a period where I was generating 5KW, with a 3.68KW limit and say 400W house draw (which is about standard during the day) then that leaves about 1KW spare, which could be used to charge the battery or it would otherwise be wasted. So if it was going to be a really good day then there would be some value in not fully charging the battery overnight and instead letting it charge at a limited rate during the high generation periods, so in the example case above, setting a max charge rate on the battery of about 1KW.

Can't see anything specifically mentioning the limit in my documentation, but I see my DNO letter does say the inverter has to be installed to meet G98 requirements (accidentally said G99 before) which I guess means it's limited to 3.68.

Out of curiosity, does anyone know what happens to the excess energy when you hit the charge limit? I've never really understood how that part of the system works, does it not get generated in the first place or is it just lost as heat or something?
 
Ron-ski said:
Don't chuck it in the "bin", stick in the cupboard with the meter so it doesn't get lost, it may be needed at a later date. When I installed the Bright app I needed some numbers of the IHD.
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It was a figurative bin (i.e. the old tech box I have in the loft). The octopus app doesn't give you real time info on cost (HA does) which is strange...
 
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