^^voltage in home is RMS(220/240v) so no need to convert it to absolute/peak values & assuming sine wave(should be true for govt power) even cheap/typical multimeter show correct rms voltage value only for ac voltage.bill is determined by energy consumed & this in turn is decided by V(rms)*I(rms)*time.since psu in pc convert ac to dc with efficiency ranging from 50-90%(depending on psu & load) there shouldn't be much difference between I & I(rms) so above calculation should give close approximation of power consumed.
this clamp meter method is used to install MCB's in houses or any other place in distribution boards because it gives accurate value
for example i have installed a new 10A C-Curve MCB ( will trip if load exceeds 10A, continously, not for milli seconds )
and my lightning load with fans and pc was 11.5A, and it tripped, so i canged it to 16A C curve MCB
this method gives really a very close approximate of the current running through the wire....
clamp meter costs 350 rupees here in local shop, no name brand