HWmonitor won't give you an actual power reading unless it supports your board's VRM monitoring IC/EPU, which is distinct from the rest of the sensors.
Without this support it will just list an estimated/rated TDP that may be completely off.
You will need to judge each board on a case by case basis when using HWmonitor. Not all boards have ICs cabable of measuring actual current draw, and many of those that do not have the IC connected to all power phases. You need to be familiar with the physical position of these components on your board and exactly what they connect to.
For example, my ASUS P6TD Deluxe has an "ASUS EPU" controller attached to half
of the power phases (8 out of 16), and only measures current draw from these phases. To get a good estimate of how much power my CPU is drawing, I need to double this number.