Simple Battery-Monitoring-Script in Python for Linux relying on the Power Supply Class /sys/class/power_supply/
Just run python battmeter.py
The output will look like this and will simply update every second:
Spannung: 11.594V
Strom: 1.693A
Verbrauch: 19.629W
Temperatur:37.2°C
If your charge the laptop the power draw actually will be the charging power.