You may want to find out the difference between kVA - kW. Well in basic electronics, you learn that in a Direct Current circuit:
Power (Watts) = Voltage (Volts) x Current (Amperes)
Nevertheless, 1W = 1V x 1A = 1VA is not always the case.
- It is true in a direct current (DC current) circuit.
- It is not true in an alternating current (AC current) circuit.
The power required by the computer is 65W. This charger will deliver 65W in DC current (Direct Current) to the computer. This is described in the red circle, and also in the bottom rectangle, which describes the output (the electricity going out of the charger and into the computer). The input (electricity coming from the plug) is a little bit more complicated, because it is in AC current (Alternating Current). This one is shown as being:
100-240V ~ 1.5A. In the US, plugs supply current at around 110V. Therefore the requirement for this power cable will be :
110V x 1.5A = 165 kVA.
One must apply a Power Factor to this AC result in order to obtain the average power in kilowatts. A power factor is a measure of the synchonisation of the phases of the Current (in Amperes) and the Voltage (in Volts). A perfect synchronisation give the Power Factor a value of 100%, and the lowest synchronation possible gives the Power Factor a value of 0%. In real life, the power factor is usually in between 30% and 90%.
165 kVA x 40% = 66 W.
This is an approximation, for a Power Factor of 40% is rather low for a computer charger, but it is a way for you to calculate your appliance's power in Watts from information in Amperes and Volts.