Why am I measuring the mains into my house? Why not just measure all the branch circuits? All else can be derived. (My case is a USA based 120/240 single phase, 3 wire system.) It’s not a huge difference, but it could free up two more CTs to refine my measurement elsewhere.
I can see how one starts this way. One might start with only a few inputs, so it’s obvious that one has to include the mains. And with some other systems, there might only be 4 or six inputs available. My pre-iotawatt system had only 4-ish inputs, so I did the mains, my solar and my car charger. And so when I bought the iotawatt, I set it up the same way, even though I started out with a full load of CTs. That is, I set it up basically as the previous system, but with more refinement. Of course, 14 CTs is not quite enough to do every single breaker in my house, but if I double up on few, I can measure every single circuit.
I have created a “checksum” output of all the loads added together vs the two mains, and the difference is usually about 6 watts or less. So the derived amounts are pretty accurate.