One way to tell what you are pulling is a couple of these meters. When we purchased them a year or so ago, they were $65 each from
Datel
We are at a friend's house and we made a splitter box and are connected to two different 20amp breakers giving us not 40 amps, but 20 amps on each leg. With these meters, it is easy to tell what we can or cannot turn on (the picture was taken some time ago).