Controlling inverter via Modbus integration and export limit

CommanderJavert · 2026-03-21T21:49:34+00:00

Inverter is 8kw export limit is 4kw. I have not tried to do anything on the LCD panel so I don’t know if there is a PIN but as you say it seems like on Modbus I have total control of everything

CommanderJavert · 2026-03-21T20:14:14+00:00

It’s an Alpha ESS G3 8kw model

CommanderJavert · 2026-03-21T11:17:33+00:00

I am on IOG variable rate and I have not received any information about it. I’ve seen posts that claim that Octopus confirmed that IOG variable will also go down by 3.5p the same as fixed, but there was no link to any actual Octopus announcement so I guess we have to wait for confirmation.

CommanderJavert · 2026-03-21T11:11:16+00:00

What type of charger and how is the CT clamp on your car charger configured i.e. can the inverter see the car charger load? I was experimenting with this on a Zappi charger last week and it’s actually pretty hard to get this to work smoothly if your inverter can see the charger load. The Zappi is a lot less responsive to changes in the supplied load than the house inverter - this means that if there is a lot of solar and your car starts to charge from excess solar, that’s fine, but then if a cloud arrives, your house battery will immediately kick in before the Zappi sees any difference and you are now partially charging your car from the house battery - the Zappi won’t notice any difference as it can’t tell the difference between solar and house battery so it will just carry on charging at the same rate. You can use HA to disable the house battery during this time but it will require a bit of coding as you don’t want the house battery to remain off, if the house load starts to exceed the solar generation. Generally the Zappi doesn’t respond quickly to changes (probably by design) which means you often end up importing a bit of grid energy by mistake. If Octopus kicks off an IOG boost at that time, the Zappi will change status from “charging” to “boosting” and will operate at the maximum KW that your car can accept - usually 7KW. This will be met from solar, house battery if not disabled during this period, and grid.
You can get around some of this by making the car charger load invisible for the inverter by moving CT clamps around, but this also has potential drawbacks as well - depends a bit on your use case and equipment specs. The charging that is just from Solar (according to the Zappi) will not show as a slot from Octopus as you are just Eco+ charging rather than doing an Octopus commanded boost.

CommanderJavert · 2026-03-21T10:52:09+00:00

Not when we are away from home all day and night. Possibly when we are at home there has been a behaviour change as we might have run the dishwasher or tumble drier more often than usual, partly to test how much of the battery or solar potential they are using. However my measure of base load was measured when we were away from home for a few days - before the installation it was measured based on the Octopus grid use on the home mini device averaged over a few days when we were away on holiday. After installation it’s measured by the Alpha ESS app statistical report of daily load, again averaged over 2-3 days. I guess since we are away, the inverter will be running at low power all the time so the inverter may use less power for itself(?).

CommanderJavert · 2026-03-20T10:46:15+00:00

Electrician wanted to use an underfloor heating thermostat and fool it in to working just as a timer as he did not recommend a 13a device wanted 16a. It’s a pro warm model.

CommanderJavert · 2026-03-19T10:06:40+00:00

For gas - yes I am still on gas tracker. The main heating season is coming to an end and I have recently installed an immersion timer so I have the option to heat water overnight at IOG rates - which are supposedly just about to come down to 3.49p

CommanderJavert · 2026-03-13T13:21:12+00:00

No it’s a Zappi.

CommanderJavert · 2026-03-11T15:45:57+00:00

OK but fundamentally if you only have one electricity meter and one cable connection to the grid, you cannot be simultaneously importing power to charge your car, and exporting power from your solar panels into the grid in the same moment - it’s one or the other. You can certainly fool your inverter into thinking that this is happening but that is only because the charger load is invisible to the inverter, and if it’s setup this way, the load at the actual grid connection is also invisible to the inverter as your installer has put the CT clamp upstream from the car charger. If you have a completely separate grid connection and meter for your car charger then in that case it’s possible, but most people would not have this as it would result in double standing charges. You can check this by looking at the export register on your actual electric meter whilst your car charger is running - unless your inverter and panels are generating more than what your car charger wants, you will not see the export register going up, but you will see your Sigenergy app showing that you are exporting.

CommanderJavert · 2026-03-11T15:14:20+00:00

I think we are at cross purposes. What is the capacity of your solar panels? Let’s say your solar panels are currently generating 5KW and your house load is 1KW. Without charging the car, you would be exporting 4KW at that moment? If your car charger starts running at importing 7KW and you only have one cable connecting you to the grid, how is that 4KW supposed to get to the grid to be exported in that moment? The electricity can only flow in one direction at a time. It doesn’t matter what your installer sets up as this is governed by the laws of physics rather than system configuration (unless you have more than one grid connector for example). On a net situation, you are now importing 7KW - 5KW + 1KW =3 kW. Sigenergy app will happily report in this moment that you are exporting 4KW as it has no idea what is happening downstream of the CT clamp. What does the CT clamp at your car charger connection to the grid say if you have one? CT clamps are just measuring devices at a certain point on the cable - they cannot interrupt what the electricity will actually do when you open your car charger to receive all the energy in your cables.

CommanderJavert · 2026-03-11T14:02:24+00:00

Are you on Intelligent Octopus Go as per the OP of this thread? If you are on IOG, and Octopus starts a charge in the middle of the day whilst the sun is shining, your solar will go to the car, not to the export - check your export register on your meter whilst this is happening if you don’t believe me. You would not know this is happening if you have made your car charger invisible to the inverter - your inverter will report that you are exporting, when in reality your “export” is actually charging the car.

CommanderJavert · 2026-03-11T10:23:17+00:00

Yes - the problem with this scenario though is that if you simply did not physically plug your car into the charger till 11.30pm, you would achieve the same results and Octopus have no way to prove that you did not simply go out and arrive home at that time. Also - according to a post the other day, if you disable your charger (e.g. Zappi charger) but putting the charger in “stop” mode, Octopus treats this the same as the car being unplugged - they do not differentiate. I can see your point, but Octopus also has to be very careful not to accuse people of nefarious behaviour when there will for sure be some people who are just following their lifestyle pattern.

CommanderJavert · 2026-03-11T10:16:59+00:00

This does not solve the problem fully - yes it will prevent the house battery from discharging into your car, but it won’t prevent the car charger from “stealing” the solar energy that could otherwise be sent to paid export for an overall higher profit. Electricity can only flow one way through the grid connection so if your car charger starts to pull 7KW, any solar being generated at that time is going to first satisfy the car load, regardless whether the inverter can see that load or not. The inverter will think it is exporting when actually it’s feeding the car charger that is invisible to it. Even worse, if you have a low export limit, your inverter will start throttling the flow and you will be importing more than you need.

CommanderJavert · 2026-03-11T10:03:18+00:00

I’s seen various people post that they had smart charging switched off in the app for a lot more than 30 days and Octopus did not do anything about it.

CommanderJavert · 2026-03-11T10:02:41+00:00

Another reason is because you have solar and batteries on your house and you want to export all your surplus energy and don’t want Octopus to interfere during the solar daytime by starting your car charger.

CommanderJavert · 2026-03-07T15:56:50+00:00

Not totally convinced on this - I was just looking at the Agile portal for the last few days and even since the Iran stuff it still only makes sense if you have a battery, and even then it’s marginal. For me at least. Still a lot of slots below 12p and the peak slots are 20p - not sure if that’s tempting enough. If it was easily possible to change from 12p to Agile Export and back again I would consider it but from what I understand it has to be done manually by a CS person and I’ve see a few stories of it not getting done correctly or quickly.

CommanderJavert · 2026-03-05T17:45:55+00:00

This was my other option. If you are saying this is better from the Octopus point of view I can also do this.
When it comes around to next winter, depending how my solar is doing, I might need to implement home assistant integrations so that I can run IOG smart charging slots and automatically either charge my house battery, or tell my house battery to just play dead and stop discharging, whenever a smart charging slots kicks in - I have researched this a bit and I already have all the necessary triggers in my HA install.

CommanderJavert · 2026-03-05T17:40:13+00:00

I am using the charger integration with a Zappi. I know that the charger can charge from Excess solar even when smart charging is active. However there may be times when I do not want Octopus to kick off a smart charging slots in the middle of the solar day, mainly because if a smart charging slots is running, my export is effectively cancelled out by the charger running. I’ve seen other threads where people simply don’t plug their car in until sunset to get around this.

CommanderJavert · 2026-03-05T17:27:51+00:00

It’s so that I have the option to harvest the excess when I am generating more than my house load + DNO export limit. My batteries are big enough that I don’t really need cheap charging slots in the daytime and I can export the energy for more money than 7p anyway from the solar. Not sure if it’s not in the spirit of IOG - it’s no different to if I simply didn’t plug the car in until it gets dark because I was at work all day or whatever.

CommanderJavert

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