UK Monitoring Off Peak power costs for Octopus IOG and Ohme EV charger

Energy
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I have Octopus IOG smart tariff and Ohme charger. I’m trying to identify off peak and peak power for use in Home Assistant specifically for the additional scheduled time outside of the off peak 11:30 to 5:30 period. The octopus rate (from the integrations) doesn’t change with the frequent Ohme EV charger smart charging, though when this happens my rate will be charged at the reduced off peak value.
I use Ohme charging state to indicate an off-peak period, which works to some degree but misses periods of off peak billing and adds periods that are actually at peak cost.

At the end of the month I get the detailed bill so I can correlate my approximation with actual bills but only after the fact. So I can robustly test my algorithm which is how I worked out my current logic is not quite in line with the bill.

I believe this is a specific consequence of the Ohme charger, other chargers lead to the octopus rate data being correct real time.
Is there any reliably determine off-peak costs?

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I use this HACS add on and it updates my rates whenever Octopus decide to charge my car GitHub - BottlecapDave/HomeAssistant-OctopusEnergy: Unofficial Home Assistant integration for interacting with Octopus Energy

Here is my current plan using Dave’s other contribution of a well presented rate card

Screenshot 2025-12-24 at 21.39.42
Screenshot 2025-12-24 at 21.39.42369×419 34 KB

3

Thanks. Unfortunately Ohme does the deciding itself and informs Octopus at some point later (I believe), so the Octopus integration doesn’t help for this setup - or at least how mine is currently set up.

I used to be able to do this when I first had just a 3pin plug charger, but when the Ohme was installed then the rates now only change during the fixed overnight period and not at points during the day.

I believe to is to do with ‘who’ is making the decision on when to charge. For most chargers Octopus is doing that, but for Ohme they have their own algorithm.