How to getthe best out of Octopus Flux

[Ron-ski]

It's Flux import only for now I think? I'm sticking on Go for now to keep costs down, even if the export rates are poor, I'm not really exporting anything at the moment.



Just go into the portal online and then into My Inverter => Settings. You can set a timed charge of the battery here.

I'm not 100% on this, but if I was on Flux I wonder if the best strategy is to:

Set charge to 100% from 02:00 - 16:00
Set discharge from 16:00 - 19:00

By doing this you will hold the battery at 100% all day, no matter the weather (excess generated solar will go to export to grid on a good day). Then export for the maximum payment you can get down from 100% to whatever it can export into that 3 hour window.

This seems sensible because you lower the battery cycles, it would be one complete cycle per day. Thoughts?

I guess it's a balance between export rate and import rate and usage. If the weather is good then the batteries will fill and there's no need to top up. I'll need to have a think about it.. problem is 4-7pm is prime cooking time so it's going to have to be a balance between grid usage and discharge.

In my suggested method above it limits the cycles, if you alternatively charge to 100% between 02:00 - 05:00 and then allow solar top it up before exporting, there is ultimately more wear on the batteries for potential small gains in the daylight hours.

Also depends if you want to attempt to export as much as possible for the maximum payment you can get.

If you can use most of your generation efficiently with Go I think that will still win in the long term, though it's a bit more annoying to min/max it.

I can't be on Go

I like your method I just need to work it out based on our usage.

The way to approach flux is going to be highly dependent on your own personal set up and consumption habits. To min max it you’d need to be looking at it daily which is going to be quite a hassle.

For me, I’d want to be holding onto about 5kwh of battery to see me though the evening peak and then just letting the solar and battery do it’s thing for the rest of the time. I’d be Charging the battery off peak in winter and not in summer.

I'm all signed up now too.......

In my mind I'd be charging to 100 in the 2am to 5am window then exporting everything else during the day and forcing a discharge between 4 and 7pm. With my gen1 inverter I could maximally charge and discharge 7.8 in this period so something like £2 every day profit on top of whatever you export which cojld be 20 or 30kwh in the height of summer and that's if you have to fully charge your batteries.

 

[Ron-ski]

It's Flux import only for now I think?

I've had an email saying that Flux import is live, but I wonder how long before export is live? My account still shows they are setting something up.

I'll need to think about strategy, but yours sound along the lines of what I was thinking. I can set the Victron a target to charge to, say 100% with a charge window of 02:00 - 16:00, it will not discharge the battery during that window. It will easily charge to 100% by 5am, so all solar will then go to running the house and the excess is exported at 25.53p per kWh. Catch is if there is low solar production we'll be pulling units at 35.31p, but our usage prior to 16:00 is usually low around baseline of 500w, so it would only be peaks that come from the grid (kettle etc) if the solar is bad, even a bad day there is enough usually to cover base load.

We'd enter the 16:00 to 19:00 with a full 100% charge, and could discharge plenty in that time once I figure out how, just keep enough back to cover us through to 2AM

To min max it you’d need to be looking at it daily which is going to be quite a hassle.

I don't think so, as long as you don't want to squeeze every last penny out of it, there is no need to micro manage it.

 

[Ron-ski]

Currently my rates are as follows

Import

Flux rate 21.19p
Day rate 35.31p
Peak rate 49.44p

Export once live

Day rate 25.53p
Peak rate 40.36p

So if my battery is fully charged at the Flux rate, it costs 21.19p per unit, lets say its empty and I charge with 14.5 units, it costs £3 to charge it.
I then discharge 13 units (allowing for some efficiency losses) at peak rate, I get £5.24, a net gain of £2.24.
We then have an empty battery, so between 19:00 and 2am we import, which will be circa 7kWh at a cost of 35.31p per kW, so an actual cost of £2.47

But any excess solar is also exported during the day, which means net gains, and I think once I have the second battery, making a total theoretical capacity of 29kWh I'll easily be able to keep some back for the 19:00 to 02:00 period.

Working it out makes my head hurt, especially as you really need to take account of efficiency losses, also DOD discharge will mean we never charge a full 14.5kWh anyway.

I'm not too fussed about cycling the battery, my EVE cells should last for 6000 cycles, which at one cycle a day is circa 16 years.

One thing to remember with Flux is the prices are variable, and not fixed.

 

[Ron-ski]

@Freefaller and @Welshman Are you also on Flux export? Only showing import on my account, although I think you both may have been exporting with Octopus already.

 

[Ron-ski]

Seems that way.

 

[Ron-ski]

https://octopus.energy/smart/flux/ and there should be a sign up link on that page.

 

[Ron-ski]

Interestingly I set up my GE to charge last night but it didn't (via the GE app not HA) - so not sure exactly why that didn't work.

Set my Victron system to charge to 60% and it did just that, thought it was going to be a bad day, but now at 100% and exporting at 4kw

 

[Ron-ski]

@HungryHippos are you able to share your spreadsheet please?

 

[Ron-ski]

Octopus Flux export is now live........

Did you do anything, mines still not updated?

 

[Ron-ski]

Octopus just told me via Twitter that it can take 6-8 weeks to complete export registration .

I wasn't registered with them for export, so I guess it could take longer than someone who already was.

 

[Ron-ski]

Slacker!

It's not me, it's them, will probably turn into another 20 week fiasco like getting the smart meters fixed.

 

[Ron-ski]

when i put my export documents to them in october it took around 10 days to get sorted and i was on smetz1 meter then too, but still half hour readings

Hopefully mine will be that quick, but with my luck probably longer.

 

[Ron-ski]

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.

 

[Ron-ski]

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

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.

 

[Ron-ski]

@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.

 

[Ron-ski]

What you're saying makes sense, as you are restricted to 3.68 on a G98.

The inverter will just throttle back generation once the export limit is reached and the house/battery isn't making use of it.

 

[Ron-ski]

Or should I just chuck it in the "bin"?

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.

 

[Ron-ski]

It was a figurative bin (i.e. the old tech box I have in the loft)

I know hence I also used "bin" as well, but if anything like mine it's almost impossible to find stuff again.

Hildebrand (Bright App) do a IHD that is live, it costs £70 though, but can be linked to Home Assistant, I may get one, one day.

 

[Ron-ski]

guess it really comes down to whether the slightly better export price outweighs the extra inefficiency of charging\discharging, and obviously it is quite a nice feeling to be basically self sufficient for electricity

It comes down to that and wear and tear on the battery, but at one cycle a day that's an awful long time.

It's certainly a lot easier than micro managing it, unless you can set up an automated system that's reliable.

The only other problem with Flux is that you now have to be careful with electric use, as each unit wasted now costs you 25p export even if you generated it.

 

[Ron-ski]

It does, but some people were being paid nothing for export, or very little, so from a financial point of view if you used all electric you generated, it made no difference, now there is a meaningful export rate it does.

In my case I was thinking of adding air conditioning, the electric would be free in the summer, but now it won't be, as it will cost 25p or even 40p in lost export per unit.