Source: http://pioneerec.com/images/VampireElectronics_000...
Study shows that many homes have been visited by vampires for at least once a day. This is not a vampire that sucks blood but these are devices that draws power even when switched off or in standby mode. Others call it phantom loads, leaked electricity, vampire draw and phantom power. If not properly monitored and eliminated it will result into increase of our monthly electrical bill.

The Transformer and the nature of vampire load

We are plugging into voltages such as 220 volts AC or 110 volts AC outlet however inside our appliances the majority used only a maximum of 48 volts DC. The change of voltage level becomes possible by the use of transformer. Therefore we can say that most of the appliances if not all have it's own transformer inside.
Technically speaking a transformer is an electrical device magnetically coupled to transfer energy from one level to another without changing in frequency. The term magnetically coupled means that the wires on the outlet (primary winding) have no physical contact to the appliances (secondary winding) and they are working by the principle of electromagnetic induction. Like magnets that can move things without physical contact.

 Schematic diagram of a transformer
Vampire loads happen simply because while the switch is off at the load side, the supply side of the transformer is still working and continue to draw current perpetually until the supply of the power itself is terminated.

To make it clear vampire loads happen when we switched off the appliances without plugging out the supply. Thus if we switched off a certain appliances and at the same time we will pull the plug in the outlet then vampire load does not exist.

Vampire loads happen simply because while the switch is off at the load side, the supply side of the transformer is still working and continue to draw current perpetually until the supply of the power itself is terminated. As mentioned above the wires at the supply side of the transformer is not physically connected to the load side but they are just working by the principle of electromagnetic induction.

Other form of vampire loads are not caused by negligence but they are also intentionally designed for convenience on the part the user. Examples of these are the "sleep mode" of the computer, photocopiers and majority of the equipments that contain remote control.

How much it costs

There are no definite record how much energy does vampire loads add to our monthly electrical bill but study shows in the some developed countries that vampire loads ranges from 10%-15% of the rated load of the appliances. That is if we are paying 110 dollars every month in our electric bill, 10 dollars of that came from the vampire loads.