Current rating ability of the energy meter. The actual loading arrangement will waste a 10t of power. The phantom loading consumes very less power as compared to real loading, because of this reason it is used for testing of meter. In phantom loading, the presser coil and current coil are separately excited by supply source. The pressure coil is energised from the small supply voltage and the current energises the current coil at very small voltage. So if the wattmeter reading is 60w, the actual power consume is much less then 60w.