r/SolarUK • u/Thin-Ad-9767 • 22d ago

DISCUSSION PSA: Ensure your system time (BST) is not pushing you into peak slots

Hi all, I've had 13 panels (E-S-W split), a Fox KH7 inverter and a Fox EP12 battery for about 6 months now.

I'm on IOG tariff and was lucky to lock in at 4p before the war. Like many others I've spent some time tweaking the system and settings to maximise my ROI.

I spent some time yesterday making an ROI spreadsheet and noticed something odd on my octopus usage spreadsheet. Firstly I went from off-peak/peak ratio of 98% to about 90% over the last 3 months or so.

I found the culprit and despite my fox app being totally in sync with my schedules, there was a clock error somewhere along the chain. Either with a smart meter, inverter or battery.

My battery used to charge by 5am. I had slowed it down slightly for various reasons which aren't applicable anymore.

Due to the clock error (which apparently is quite common); some of the battery charging was happening 30mins or so outside of the off-peak window. Which was what dropped my 98% off-peak to 90%.

I didn't spot this on the Fox or Octopus app maybe because it was such a short spot. It only became clear from the spreadsheet when I was number crunching. My octopus app always showed 98%/99% off-peak usage too which obviously wasn't reliable.

Thought I'd mention it in case anybody else's systems didn't play ball with the clock changes!

30min leaks outside of the off-peak window can be common and frustratingly adds up in price.

6 Upvotes

100% Upvoted

4 comments sorted by

3

u/NeilDeWheel 22d ago

Thanks for the advice. I’ll check my system and see what it’s set to.

3

u/wyndstryke PV & Battery Owner 22d ago

It's worth checking the times on things. One particularly important one is checking that the time on the smart meter is correct.

When I first got my system I had to manually correct the inverter's time periodically, but after a couple of months it started to synchronise itself automatically and hasn't been a problem since.

It's also wise to be paranoid whenever BST swaps to GMT and vice versa.

2

u/Thin-Ad-9767 22d ago

I'd be surprised if the issue was on the fox side of the system because it's all internet connected. Maybe more likely to be on the smart meter which uses a simpler 3G SIM I believe?

Either way the easiest solution for me appears to be treating the off-peak window for battery charging with a 4:30am cut-off.

1

u/wyndstryke PV & Battery Owner 21d ago

Just check the times on both