Think you have answered most of your own questions but just to confirm.

On IOG you will always get 11.30 to 5.30 cheap rate every day regardless of whether the car is plugged in or not.

When the car is plugged in a schedule will be made based on how much you need to charge the car that could include extra slots but they are based on whether you need them to fill the car to the specified level and when you need the car ready by plus the best slots in terms of the grid.

In those slots you can run your heating and charge the batteries but unless you use something like home assistant you are doing that manually.

You don't say what car or IOG integration you are using, if its an Ohme charger you need to unplug after every charge is complete, some people found out the hard way that if you don't unplug after a charge you get billed at peak rate as the data isn't sent to Octopus till you unplug.

@gary interesting - thanks.

I've got a zappi. I have not been unplugging... so far. Any idea if necessary with zappi?

Car is MG4

I'm using WonderWatt to help manage charging batteries. It picks up the adhoc daily slots as well as fixed overnight. So far I feel its worth the cost for the simplicity. But will see over coming weeks.

@tim441 Zappi has better integration with IOG so no need to unplug.  If wonder watt picks up the extra slots then thats a great solution for you.

The only extra thing I do, is use the heatpump app to change between fixed flow at 45C between 11.30-5.30 and then change it back to weather comp during the day.

Works well, to preheat the house saves anything from a few hours peak heating in the depths of winter to never having to come on during the day at all in the spring and autumn.

I managed 7.64p per Kwh import in 2024 and a negative bill if you count export.

@gary wow! That's really impressive. Good tips.

I was at 12p on Agile last year. But I think I can make IOG work for me even if I pay the day rate for a few hours.

My heat pump is LG. App and controls poor - especially for my 2020 installation. So I don't think I can automatically use fixed flow at night. But will check options. Main thing is I won't use any setbacks at night. 

Today is only 4deg outside and minimal solar. But batteries still at 50%. So hopeful I can use say 5kw at day rates out of 40kw imports

IOG offering a lot of cheap daytime slots today. Despite cold, grey day.

Car was unplugged and used this morning so maybe helped kick the additional slots into action.

I guess wind is blowing somewhere?! And grid balancing needs?

Anyway.. Nice... filling car.. filling battery... ashp warm house... 46kwh imports so far. Almost all at 7p

With battery I suspect I may pull close to 100kwh today. But average likely to be around 8p.

Conclusive evidence after 2 weeks on IOG.

Batteries plus extra daytime slots ensuring average is under 10p kwh/day

IOG 5th to 17th in pic - vast majority at 7p/kwh

1st to 5th Feb I was still on Agile 😱. Octoprice suggests my costs for 1st to 17th Feb if I'd stayed on Agile would be £276. Allowing for some changes in patterns of charging I suspect  it would be at least £240 anyway. If IOG for entire month I expect it would've been closer to £100

So is IOG better than Cosy?

@carpenterstation I don't think its possible to give an absolute yes/no... as every situation is different.

I am a moderately heavy user I think? Importing around 10k kwh/pa.

Having solar, batteries, ev

Batteries important to help minimise daytime rates.

6th to 18th Feb 931kwh £71 = ave 7.62p
Ex-vat
Ex-standing charge

so even during such cold period I was almost entirely cheap rates 

Posted by: @carpenterstation

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So is IOG better than Cosy?

That will depend on your usage and storage capacity. IOG has a super cheap rate overnight, so if you can charge your battery overnight and then use it to power your house all day then that will be cheapest, but that requires large batteries, especially if you have high usage with a heat pump (we can easily use 40kWh per day in winter so would realistically need maybe 30kWh of battery storage).

Cosy gives you 3 cheap slots spread across the day. They are not as cheap as the super cheap overnight rates on EV tariffs, but there are only 6h between each cheap slot so a smaller battery would enable you to stay within cheap rates - in my case, maybe a 10kWh battery instead of 30kWh of storage. We are on Cosy, and I'm currently in the process of adding a Telsa Powerwall 3 (13.5kWh) which should see me through the 6h slots between cheap rates bringing my effective import rate down to the current Cosy cheap rate of 12.8p. We would need 2-3 Powerwalls (and an EV) to make the IOG tariff work for us.

If you go the larger storage route, this opens up other strategies in summer to leverage any differences between import and export pricing, to fill the batteries at cheap rate and then export it for profit at a higher rate as you would have way more storage than needed. Conversely, a PW3 at 13.5kW is sized at around our daily usage in summer, so with solar topping it up each day, we are unlikely be importing anything in summer and exporting any excess.