I've actually got two meters I had to track - one for solar production, and the main one which tracks power from the grid and power out to the grid. So I can figure out production from the solar meter, how much I've sent to the grid from the main, and usage by adding power in from grid and (production - sent to grid).
So after dark, the only power is from the grid - and that's spot on. During the day things are thrown off by Sense's determination of production. The main cts are accurately measuring in-and-out, though because production is measuring low, measured use is low (often zero or negative).
I knew very quickly after our solar panel install that the inverter was over reporting by 3% or so, it's one of the reasons I bought sense - for more accurate readings (and to ditch the zigbee connection). Sadly, Sense is also plagued with errors
I spend way too much time looking at this data I was a little apprehensive about whether we'd recover our solar investment. We'd be OK if Aps would lay off the metering changes...