The key to all of this is the differential between Octopus Intelligent Go and SEG payments from Octopus, (or any other provider). 7p inbound against 15p export with Octopus. You need to ensure that you export all of your Solar at 15p and have enough battery capacity to store electricity at 7p. Overnight you have to charge the EV and topup the batteries as well as heating your hot water with the immersion heater during to Off Peak time slot, which is very generous 11.30 - 5.30 all at 7p. During the day, and up to the 11.30 off peak period, the batteries will cover your background usage, fridge, computers, etc. All of your Solar is then exported at 15p. The Intelligent Octopus with the Ohme charger can sometimes charge outside of the Peak period but is always just costing you the 7p rate regardless of the time. The secret is having enough battery storage to cover your daytime usage and to ensure that you don't use any peak kW.
Winding this back to the beginning, this is now relevant to my interests and I wish to learn more.
When my system was installed in May I had no export tariff, so the priority was using as much of the solar as possible and minimising grid imports at any time. The way the system was set up this worked pretty well, with most weeks being less than 20p in grid import, mostly transient chatter among the components of the system. The battery would support the house overnight, then the solar would take over at sunrise. When excess started to appear the first priority was recharging the battery, then heating the water with the Eddi, then after that I would usually grab everything for the car unless it was already full. If I used more electricity above the house base load, this would come first from the solar excess, then from the battery. If the battery contributed at any time, it would recharge on the solar before anything else got a look in. The result was that the battery was always at 100% at dusk, and ran the house from then until sunrise, when it began to recharge on the solar, rinse and repeat.
This was all fine other than the fact that with the best will in the world, and despite the poor summer for solar, and running the car exclusively on solar all that time, I still chucked an insane amount back into the grid for no payback.
Now I have the export tariff I'm having to learn how to turn it all round and try to live as much as possible on the 7p overnight tariff so that I can export as much of the solar as possible. I don't think I'm doing it right. I can see the above method is the way to go, but I'm not there yet.
I set the battery to charge 11.30 to 5.30, fine, but that means at this time of year that the battery never gets below about 95% because it is charging on both the off-peak electricity at night and the solar during the day. It only has to support the house for about an hour in the early morning and about three hours in the evening. I got round that by exporting what was left in the battery at 11.30 then recharging it from 2am, but there seems to be some dispute as to how permissible this is?
What I really want to do is what Chris is doing. I have a 9.5 kwh battery and as far as I can see that's enough to support the house from 5.30 to 11.30, at least most days (I don't have experience with winter consumption yet). But I don't know how to stop the battery, then the Eddi, then the Zappi, from grabbing the excess solar. I can turn the Eddi off when I wake up and turn it on again in the evening, but that's a question of remembering. Every bloody day. I can leave the car unplugged until after dusk, but that means going back out again in the evening to plug it in, which is a bit of a pain.
But even if I do all that, I don't know how to stop the battery recharging on the solar. I don't know how to stop the house using the solar first for any load it needs. And even if the load is such that it does use some of the battery, the battery obligingly recharges off the solar as soon as the load has ended!
I have a standard GivEnergy setup with a 9.5 kwh battery and a 5 kw inverter. The water heater is a MyEnergi Eddi and the car charger is a Zappi. What am I missing here, please?
