Hi Margaret,
Welcome to OEM.
OEM is a whole-house monitoring system. Although it can be expanded / adapted to multi-circuit monitoring, there’s a newly developed device called IoTaWatt that would be well suited to your application. IoTaWatt is not yet available, but the OEM Shop hopes to have a small quantity of pre-production units in the next few months. See this post.
Just above, and to the right of the upper circle, is what appears to be 4 AWG. I can’t tell for sure because the photo is blurry. The number to the left of the letters AWG is the wire size. If the printing on the wire is 4/0 then the answer to your question is yes. If so, you’ll need one of the alternative CTs, as the SCT-013 sold in the OEM shop won’t fit wires of that size.
Yes
All of the breakers in your load center are rated at 20 Amps, so you’ll want a 25 or 30 Amp CT for each of the branch circuits you want to monitor.
When choosing CTs, keep in mind you don’t want CTs that produce an ouput of 0.333 Volts.
What you do want is a CT that produces either A) an output of 1 Volt, or B) a current output, sometimes referred to as a milliamp, type CT. Another name for that type of CT is unburdened.