I recommend you just ignore the negative post. Maybe the moderator will delete it.
The best way to find out the power draw of 12 volt appliances is to install a shunt type monitor. It requires a shunt be attached to the negative terminal of the battery and a read out mounted some where convenient.
Less expensive models have a telephone type cord between the shunt and the read out. These monitors usually compute battery state of charge and wattage as well. Some of the more expensive ones have blue tooth and cell phone apps.
I wish you good luck and happy trails ahead!