@toodles  Thank you for sharing that. I note you have a small amount of consumption at peak rate (7.1kWh). Were you expecting that, or is that Octopus doing funny things with your battery?

The reason I ask is I noted on a YouTube channel a reviewer observed that Octopus would never discharge their battery fully down to 20% during the peak, but would stop the discharge at ~24-25% and then they would end up importing a small amount at peak rate for the last 15mins or so (18:45-19:00), even though there was spare battery capacity. I wonder if you are seeing similar behaviour?

@old_scientist I have been imitating a hawk towards the point when the Powerwall remaining capacity nears 20%; on the first few days, there was some overshoot and ‘Constantine’ in his octopus wisdom started to recharge the battery during peak time.

During subsequent days, this has improved as the algorithms learn my system’s capacity and likely solar contribution. Today, I don’t think there was any overrun at all.

What happens is that when it reaches 20%, the discharge from battery ceases and it just takes any remaining available solar. If and when the solar no longer provides as much as the house demand requires, the system will just take enough from the grid to keep things ticking over until 19:00 when we return to the standard rate again. I find that Constantine usually starts to recharge at 23:00 and by the morning, I may have 50-60% (sometimes more) charge awaiting use. Solar then tops this up so that when we reach 16:00, we have 20+ kWh to export to the grid plus ‘real time’ solar on top. Long before this, the battery is usually full and excess solar is being exported at the standard rate (still higher than the Outgoing Fixed Export rate). At such times, the system is exporting to the grid at ~14kW for the first hour or so then tapers a little. I will report in greater detail (and confidence!) next month when I have a full month’s results to work with. Regards, Scrooge err… I mean Toodles.

@toodles thanks for the analysis. I'll be really interested to hear how well Octopus manage the charging and discharging of the battery once things settle down and you have a little more data. Trying to predict how much to discharge during the peak rate slot, and still leave you enough charge to run the house must be difficult, especially if some evenings one decides to turn the oven on at 6pm and on other evenings you're outside grilling on the BBQ with excess solar. Maybe in the height of summer it's less of an issue as solar will be stronger for longer, so house load at the end of the peak period is more likely to be covered by solar and less dependant on battery (although my electric oven still pulls 2.7kWh so we'd have a 3kW base load).

It would be nice if Octopus allowed export down to 20% and then house load only down to 10% to give a little in reserve to cover house load if required.

@old_scientist I have written to OE on the subject of discharging to grid down to 20% then allowing house load to use battery down to perhaps 10% - I don’t see the point of using the grid during peak demand time (and subsequent higher rate for consumption too during the last half hour or so of the ‘spensive block).

Rather than formulate my feelings on using IOF with just experience of one month, I’ll wait for a further month; there were some heat pump on days in April despite the sunny days. The heat pump is less likely to be used in May and may provide a more meaningful example to base my typical consumption and solar production on. I’ll report back in in early June if I may. Regards, Toodles the Scrooge.

Posted by: @toodles

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@old_scientist I have written to OE on the subject of discharging to grid down to 20% then allowing house load to use battery down to perhaps 10%

Thank you - I await your update  

Our average import rate on Agile for April was 15.4p. The first half of the month saw no heating, with a little heating in week 3, and the last few days again with no heating requirements as temperatures soured. We are still awaiting the outcome of our G99 application for a PW3 which has been over 2 months now. We may or may not get things sorted in time to switch to IOF this summer.

@old_scientist We are with SSEN and our G99 application took over 12 weeks then in 2022.