I’ve been waiting for a couple of days of consecutive sunny weather and finally they arrived. The news was as good as i hoped it would be. There are several ways to show this, so lets start with Graph 1, the full 24 hours for Saturday.
The graph shows mains draw in white, Solar generation in yellow and battery charge and discharge below and above the line. It was a beautiful clear and cold day, the Solar generation is almost a perfect curve. Mains draw fell to zero as the Solar took over, and stayed there except for some tiny blips throughout the day.
Once the sun set the Powerwall took over, and ran and ran. There was still around 12% charge on Sunday morning, another clear day. Graph 2 shows the next day and does include mains draw, but there is virtually none. Graph 3 shows mains on its own, and it is tiny, only 0.2 kW from midnight to 4pm.
The Sunday charge ran through until Monday morning. By the then the weather had changed, and it’s now cloudy, cold, and snowing. Before that happened we were effectively off-grid for 48 hours.
That’s not all. Part of the installation was an additional switch to divert current to the hot water tank immersion when there was sufficient charge. We’re having our bathroom refitted, that fat spike in Graph two around 8:30 – to 9am is the immersion heater kicking in after a long hot bath, the first we’ve had for a few days. No gas was used to heat that water, just sunshine.
There are a couple of things I don’t understand: why there is that mini draw from the mains when the Powerwall is charged, and what the rules are for the immersion discharge. I’ll talk to the installers and report back. I’m not concerned, these two days have really proved the functionality of the system.
Can’t wait for the summer now!