Twice in the last couple of weeks my Sense monitor has been showing nonsense solar power readings.
Normally, the power graph shows what you’d expect, with daily peaks in the orange solar power graph around noon every day.
Then, around 1am on 22nd May, the Sense monitor started reporting that in the middle of the night the solar panels were suddenly producing an amount of power exactly equal to what the house was consuming. In the morning, when the sun actually came up, the monitor reported negative solar power production. Around 8:45pm there’s a 15 minute gap in the graph, and then around 9pm the graph resumes showing sensible data again.
It happened again about five days later. Around 11pm on 26th May the same thing happened. The Sense monitor started reporting that in the middle of the night the solar panels were suddenly producing an amount of power exactly equal to what the house was consuming. In the morning, when the sun actually came up, the monitor reported negative solar power production. This continued until 8:54am on 28th May, where there’s another gap and then the graph resumes showing sensible data again.
While this was happening I took a screen shot of the “Monitor” screen.
Making sense of this is harder than it should be because what Sense displays as “Mains” is not the power coming in on the service feed. It is actually the sum of service feed + solar generation. It would better be labeled as “House consumption”. For example, if there’s 1kW coming in on the service feed and 2kW solar generation, the line labeled “Mains” shows 3kW, which is actually the total house consumption (combined total from both power sources) at that time.
On the left phase the two values are identical, and negative: -2916W. It is as if the Sense monitor is reading the current power on the service feed (which is in fact negative at that moment due to daytime solar surplus) and then using that reading for the solar. It’s reading zero for the left phase service feed, so 0 + -2916 = -2916 is what’s displayed for “Mains” (sum of service feed + solar generation) for the left phase.
On the right phase the Sense monitor is reporting 4768W consumption and 0W solar production, both of which are also obviously wrong. At that time of day 4768W is more plausible as the right phase solar production (this matches the data directly from the solar inverters, which also have Wi-Fi and a web UI). It seems the Sense monitor is reading zero for the right phase solar power, so it displays zero for that value. It’s correctly reading the actual current solar power as 4768W, but then using that value as the service feed power. What’s displayed for “Mains” (sum of service feed + solar generation) is therefore 4768 + 0 = 4768.
It looks like the Sense monitor keeps getting its current clamp inputs mixed up. I might assume I’d wired it wrong if the problem were consistent, but it happens occasionally and then fixes itself. I’m sure I’m not in the habit of rewiring my main panel around midnight.