Every week since I finally got my export tariff the value of my export has very comfortably exceeded the cost of the mains electricity I have used. I had my first export payment on 17th September which came to £130.58 for about five weeks. So that isn't bad. The mains power used includes routine car charging too. (I don't bother to count what I use from public charging, because it's still on a par with what I'd have used in petrol if I'd been doing the same trips in the Golf.)
I'm OK about the way the system works now. Sure, I'd prefer to run the house off the battery during the day and export all the solar, but what I'm doing is working. My only remaining issue is that I don't see a way to automate the export of the remaining battery content at the end of the day. I can work out a rough protocol, but the time varies from day to day depending on both how much solar there is in the early evening, and especially on how much electricity I use between the point where the solar can no longer support the house load and the point where I start to force the battery export. This means that I can't simply set it up and forget about it. I feel there should be a way to automate this, but as I've been away I haven't followed anything up.
While I was away it was possible to ignore it, because the house was just on its base load throughout the evening and the evenings weren't especially dull, so leaving the export start time at 9.30 worked fine. Once I got home I changed that back to 9.45, which gives enough leeway for a bit of cooking and for the central heating boiler to be running, as is now necessary.
This won't last though. Today is the worst day for solar I've had yet, by a mile, only 1.8 kWh. It's been overcast and raining all day and generation has struggled to support the base house load. The battery struggled up to 100% a couple of times, but then started to discharge again, and is already down to 86% at half past seven. This means, clearly, that the start of the export will have to be delayed quite a bit tonight in order not to finish before 11.30, as it will be starting from a much lower SoC.
I expect there will be plenty more days like this during the winter, and indeed days with even poorer generation. It's a royal pain to have to think about what time the export needs to start every single day. It's really the only fly in the ointment.
I note that almost every day during September I exported a bit more than I generated, by way of emptying the battery at the end of the day. The only two exceptions were the day when I tried out the "free hour" and lost an hour's export as a result, and a day when I started the battery discharge too late (Octopus had given me a start time for a charge of 10.30 and I forgot to change the start of the battery discharge to an hour earlier.) So I'm not losing out.
My main problem is a psychological one. When I was paying full whack for my electricity I didn't bother about what I switched on and when. I just paid the bill. My usage was genuinely excessive. But now I have this system I've swung to the other extreme and I'm being ridiculously parsimonious. Rightly or wrongly I feel that every kWh I use in the peak-tariff period is a kWh I could have been exporting for 15p. Why is this bothering me? I think because I paid out a fair whack of a capital sum for the system, and a little voice in my head is saying, you've got to recoup your outlay.
This is actually silly, because the point of the outlay was to allow me to go on using at about the same rate I was before (with the exception of the savings generated by switching to low-energy light bulbs, which I have decided I like after all), except much more cheaply. I expect I'll get over it and find a middle ground as I get used to using the system.
