FoxESS Community - Owners & Installers Forum

I'm very new to IOG, and before that was with EON and charged my EV in their off-peak hours.
Now that I have a Solar+Battery installation, I have a question that is confusing me.
If I request my EV to be ready at 05:30, the charger turns on during the off-peak hours, and all is good. I pay 7.5p/kWh for the charging. This is also the time I do a battery charge.
If I request the EV to be ready during peak hours (I haven't done this yet), I assume IOG just charges during peak times (what else can it do?). If I have surplus solar and a charged battery, where does the charge for the EV come from, and how is the cost calculated?
I assume no grid import, IOG will see that my EV is charging, but surely the charge is derived from the solar or battery.

Where the power comes from is determined on how the EV Charger is wired up.

The normal process is that the EV Charger is wired up in your meter box via Henley blocks so that the energy is split from your solar. Then you will have CT Clamps from your solar system that measures the power AFTER the splt so that the power that goes to the EV is not even seen by your solar system, this stops the battery from draining.

Without knowing how your system is wired up, it makes it hard to answer your question fully.

Grumps wrote: ↑Wed Mar 04, 2026 12:32 pm If I have surplus solar and a charged battery, where does the charge for the EV come from, and how is the cost calculated?

I don't think it's wise to drain 1 battery to charge another, they do wear out.

What I've been doing is to force charge, even at just 1W, at the same time the hot water system pulls from the grid, so the battery won't try and supply to it.

Check Will's post here regarding the Henley block and wiring.
viewtopic.php?p=9631#p9631

So if yours is wired this way, it won't be draining you battery, the EV charging power is invisible to your solar system and you don't use PV or battery power to fill your car.

I agree about draining one battery (Fox) to charge another (EV).
My wiring is as follows - only a single CU:
So, as it stands, if the solar is generating 5kW (as it is now) and IF the EV was charging at 3kW (which it isn't), then there would be 2kW flowing through both CTs, the meter, and to the grid. What does Octopus think about this? Is it just a SEG of 2kW, or does it want something for the charging?

And if there were no solar generation and the EV was still taking 3kW, there would be an import of 3kW. Does Octopus charge this at 7.5p/kWh or what?

If I understand correctly, the better wiring would be (with an additional mini CU for the EV):

Hi Grumps,

So with your current setup, you are similar to me (wired different, but outcome the same) where your EV Charger is just seen as a load by your Inverter, so it supplies power to it, thus should drain your battery rapidly.

I have my Inverter wired up to a Home Assistant that makes the Inverter charge the battery when it sees Off-Peak rates being applied, so this tops up your battery if you get any random daytime slot, or charges it during the night.

You have two choices here, setup Home Assistant to automate this, or as you are seeing, option two is to split the power that comes out of the meter via Henley blocks and wire your EVCP off one split, and your house (and Inverter) off the 2nd split. Placement of the CT clamps makes the EVCP use totally invisible to your Inverter, so it does not drain the battery.

Grumps wrote: ↑Wed Mar 04, 2026 2:49 pm So, as it stands, if the solar is generating 5kW (as it is now) and IF the EV was charging at 3kW (which it isn't), then there would be 2kW flowing through both CTs, the meter, and to the grid. What does Octopus think about this? Is it just a SEG of 2kW, or does it want something for the charging?

And if there were no solar generation and the EV was still taking 3kW, there would be an import of 3kW. Does Octopus charge this at 7.5p/kWh or what?

So in your example, if the PV was making 5kW and the EVCP was using 3kW, then 2kW would flow out to the grid. So you would get your SEG payment for 2kWh if used for 1hr of charging. So Octopus wouldn't have a clue and you get paid for this.

If no solar, and the EVCP wanted 3kW then you get charge 7.5p per kWh or most likely 30-32p per kWh as peak pricing. The Intelligent part of IOG means it should charge when they instruct your car/charger (depends on how you paired up) and it will then be on the cheap rate of import.

There is a fair bit more to talk about with IOG, as there are changes coming at some point (they are currently delayed)