Getting back to the performance of my own system, I have refined it so that I can easily harvest anything that would have been clipped by the 5 kw export cap, as I was describing earlier. The settings, once set up, are easy to control.
The battery charges at the cheap rate overnight, having exported whatever is left just before 11.30. it stays on charge till 5.30 so that the house uses mains electricity until the end of the cheap rate. I then have an export setting from 6.30 till 8.30, which is long enough to get the battery right back down to about 20% if desired. This is late enough that the house will be running on solar by the time the export has finished, so there's no risk of importing peak-rate power. I take a minute in the evening to set the export limit depending on the weather forecast. If it's wall to wall sunshine, particularly if it's not that warm, I could go down to 20% - it's possible to pick up 80% on a really favourable day, usually in April or May. I usually go for somewhere between 30% and 50%. The idea is to leave enough room in the battery for the possible extra generation, but at the same time to have enough there to run the house and cook in the evening if the solar doesn't live up to expectations. If the forecast is terrible I just turn off the export setting for that day.
After 8.30 the export limit is changed to 100%, to keep the battery from charging from the solar during the peak generation time
unless the 5 kw export limit is exceeded. If it's a sunny day I don't need to worry about anything, but if it's cloudy at the time I want to boil the kettle I have to remember to switch the export off temporarily or it will draw a bit of mains power. If it's really dark with rain clouds and I have the central heating and the hi-fi on so the house base load is high, it's possible for it to draw mains power at that time too, but frankly if the weather is that bad it's best just to switch off the export and forget the entire thing.
I have the export set to finish at 7.30 which is about when the solar stops supporting the house, but I often switch it off earlier if I'm wanting to cook. All that happens is that the solar goes into the battery to be exported later, so I suppose a 10% loss which ain't much on a small amount anyway.
The next place I need to do something is mid evening, decide when to set the export to start so it finishes as soon as possible after 11.30. I've got quite good at this. I tend to set that and decide where I want to export to the following day at the same time, so not much fiddling.
Is it worth it? I reckon I made about £15 in May this way, on top of £100 regular export - it was a very good month for solar. Less in other months. If it wasn't worth it I don't have to do it, it's just so damn
satisfying to grab that extra bit of generation that would otherwise be capped by the G99 export limit.
I always said I didn't want to be fiddling with it, just set and forget. I'm still fiddling a year later. But "set and forget" exists and I could do that if I didn't want to fiddle. Just lose a small percentage of my returns.
Here is a day where I only exported to 50%, expecting poor weather, and I got the battery right up to 100% before the clipping stopped. (The left hand side of that graph is what happens when I forget to set the evening export until way too late - export went on till about 12.30 am. The right hand side shows it finishing at 11.30 pm because I remembered.)
Here is a day when I expected it to be good so exported to 30%, but due to a fairly extensive cover of high light cloud the generation didn't often exceed 5 kw. It was still a nice day, but this game needs at least periods of clear blue sky.
I'm noticing a much more marked effect of temperature than I had imagined, and I might even start a separate thread on that.