Turn off the PC and unplug it from the wall
Open the computer case
Look for the metal box where the power cord plugs in
Check the back-top or back-bottom area of the case
Find the label on the power supply unit
Read the wattage and model information on the label
If needed, trace the power cable from the wall outlet to the PC
Use the motherboard and component power cables to identify the unit
Check the PC manual or manufacturer website for the power supply location
If the case is sealed or compact, inspect the rear panel for the power input area