I used a couple current clamps to monitor the energy for a while in my apparent and it's surprising what you can learn just from monitoring the total power used. I'm in the US where we have two 120 volt legs to ground. Small loads are connected between 120v and ground (more correctly called neutral) and larger loads like the stove, water heater and electric space heaters are connected between the 120v legs to operate on 240v.
Looking at the traces of current vs time, you can see:
1. Regular repeating load on one 120v line ā the refrigerator cycling on and off
2. Somewhat regular cycling loads on both 120v lines ā electric space heaters cycling on and off
3. Simultaneous increase on both 120v lines immediately after starting a shower and continuing for a period of time after the shower is completed ā electric water heater
I was truly surprised by how much could be reasonably determined from two measurements. While you can't isolate a particular circuit, by noting where a spike occurs and the activity going on or even just knowing the time, you can make some good guesses as to the cause.