"Ghost" power output that should be zero


I have a weird issue with some amount of Wh being reported in homeassistant but I think the source of “faulty” data is iotawatt. I can’t quite pinpoint what the issue is. Iotawatt seems to accumulate some tiny amount of power continuously starting around 2am and that goes on until sun hits my solar panels and they are actually producing power.

Output config (compensating for erroneous solar CT readings at night/winter):

How it shows up in homeassistant. The false increase in Wh doesn’t start until 2am for some reason. Power output should be zero until 8 or 9am, or none at all (I live really far north and have snow on my panels for most of the winter).

When I group the graph by “all” I get an output total that matches the homeassistant data:

Continued below due to embedded image limit.

But when I group the data by “auto” I get zero output:

How can I resolve the false readings? In December, when my solar panels were completely covered in snow, this error added up to 4.3kWh. Same thing, reports as zero in IotaWatt when “auto” grouped, but the total matches homeassistant when grouped by “all”.


Let’s start out by redefining some of these observations:

What you are calling :ghost" power is probably the standby power that your inverter uses when the sun don’t shine. It is a legitimate load. If your inverter CT had “allow negative values” set, you would see it as a negative value at night.

What you are calling “false readings” is actually a discrepancy in the way you are using the data, and a manifestation of trying to “clean up” the legitimate standby power by subtracting 12 Watts from the inverter output.

The way outputs work is that they perform the calculation on each increment of any particular query. When you set the increment to “all”, there is one increment and you subtract 12 from the daily total - essentially resulting in no adjustment at all.

When you set the increment to “auto” the graph shows that the data is in 20 second increments, so 12 watts is subtracted from each increment and so each increment, to the extent it is 12 watts or less, will be zero. When you add them up, you get zero.

It’s hard to grasp how this works, and I’m not going to try to go further here. If you research back in the forum, you will find some more detailed information. The good news is that this problem can be remediated using an integrator.

I would suggest that you look at integrators in the docs, and set your inverter CTs to allow negative values. Then use the integrator .pos and .neg to distinguish between power produced by the inverter and power consumed by the inverter.