My Powerwall and gateway was installed last Friday and I’ve put in on time based control. I’m currently on Octopus Go at 7.5p off peak and 35p on peak.
When it was installed on Friday, it had 20% battery but we had very little solar that day so I hit reserve very soon and started to take peak power from the grid on Friday afternoon.
The Powerwall filled up to 100% overnight (Saturday morning) and we produced only a small amount of solar again on Saturday (4kwh) but the battery lasted the day, with no peak power taken from the grid.
The Powerwall charged back up to 100% overnight (Sunday morning) and Sunday was similar to Saturday in that the battery lasted the day (5kwh from solar and no peak power from the grid) and had about 25% left when I went to bed Sunday night.
On Monday morning, the Powerwall only charged to 58% overnight. Not sure why or what prompted this. There wasn’t a lot of solar on Monday (4.5kwh) and the battery managed to last the day (no peak power again
) but was only just above reserve when I went to bed ( I have reserve set at 15%). The decision to charge to 58% looked a sound one although I did think it had undercooked it when I first checked the app on Monday morning.
This morning the Powerwall charged back to 100% which I was not expecting it to do as solar generation looked more promising for today. As 10am, I have already generated 4kw from solar, the battery is full and am exporting to the grid which I was hoping not to do. I was only expecting the off peak charge to top up to around 50%, not 100%.
The cost differential is nothing really, 7.5p paid off peak use vs 4.1p credit to export to the grid but it would be nice to understand why it does what it does.
The only difference on Sunday night/Monday morning when the battery charged to 58% was that the car wasn’t on charge that night. It was on charge all the other nights when the battery also charged to 100%. I don’t know why this would make a difference and suspect it is just the gateway learning my usage habits.
My house is on single phase, 100 amp fuse and pulls 12.9kwh off peak – 7.5kwh for the car, 5kwh for the battery and a few hundred watts for the house. We use around 10,000kwh per year (4.5 for the car and 5.5 for the house).
Anyway, enjoying my purchase so far, if not a little too keen to be constantly checking on the app!