|Slightly misleading as battery is charging!|
Part of it was making a power cut. This was interesting.
So a few facts that are useful to know.
- A real power cut means a couple of seconds of no power. It is not seamless.
- A deliberate "off grid" (done on the app) does not, so if it is a planned power cut then you can seamlessly go off grid if needed. Good.
- Going back on grid is seamless, a few seconds while it sorts phase match and back on. Good.
- It will take solar during a power cut, and charge the battery if needed. Good.
- If the solar exceeds its 5kW charging capacity it will shut down the solar (done using frequency change, apparently).
The last point is a pain as the solar can do 10kW. More importantly the solar can control what it makes by de-optimising the panels, so it if knew it was a problem it could reduce power. There seems no way to link these intelligently, sadly. But once I have a second battery we will be fine at it will match the battery, at least until the battery is full. What I don't know is if there is any way it tries to turn the solar back on in such cases, maybe trying it for a few seconds every now and then? Must find out.
And as for the first point, a power cut causing a blip - I need a very small UPS for my comms rack to last a few seconds, that is the easy part.
One battery can handle 5kW in/out, and charge to 14kWh. This is fine for most cases for balancing the solar and usage and reducing export. It is also perfect for getting on the Octopus tariff for this where they manage the battery and I pay for net usage.
However, one battery does limit my options. It does not have capability to run the house for 24 hours, meaning that I cannot make use of "cheap charge at night and run of battery for the day". If I could, I would save even more, but without that I could be using more expensive electricity later in the day, especially in winter when less sun.
One battery is also likely to have the same issue if I went on an agile tariff, in that trying to match charge at low price and usage when high would be hard if I do not have a whole day's capacity.
So for these various reasons, a second battery is on order. For now, I am trying to sort the Octopus tariff, which is fun.
The other work still planned is an additional small consumer unit that has a few circuits which will not be on backup. The Tesla can only do 5kW, so if I have the tumble drier on, or the car charger, it won't work. There are about 4 circuits to move to that. All good fun.