VA to KW Calculator
The SI unit of power is Watt (W), and the power of 1W means that 1 Joule (J) of energy is consumed or generated every second. In other words,
W=J/s.
Electrical power is the rate at which the energy is consumed or generated in an electrical circuit, in other words, it is the charge (the unit is Coulomb, C) that passes through an electric potential (the unit is Volt, V) in the unit of time. That means that:
W=(C*V)/s=V*A.
But if W=VA, why are W and VA not the same?
The thing is, the upper statement about electrical power is only true when energy flow always goes in the same direction and Volts and Amps are in phase.
But alternating current (AC) circuits usually have energy storage elements (capacitance or inductance) that cause not only periodical changes of energy flow, but also Amps and Volts to change out of phase.
Due to that, power cannot simply be calculated as Volts times Amps because they constantly change, but a more complex formula is needed to describe these relations.
Real power is the power that is being used in the circuit, it is the mean voltage over time times mean amperage over time.
The unit that is used for real power is Watt.
Energy storage elements in alternating circuits don’t dissipate power, but because they cause drops in voltage and amperage they create an impression that they do, and the amount of power by which they seem to change the power of the circuit is called reactive power.
The overall effective power of the circuit is a combination of real and reactive power and it is called apparent power.
To distinguish real power from apparent power, the unit of measurement used here is the Volt-Amp.
The ratio of real power to apparent power is called the power factor, and it can be anywhere from 0 to 1.
The higher the power factor is, the more effectively electrical power is being used.
What is the formula to calculate kW from VA?
The formula to convert VA to kW is:
kW=(VA*pf)/1000,
where VA is the apparent power in Volt-Amps, and pf is the power factor.
The part of the equation in the bracket, VA time power factor, converts power to Watts, but because 1kW=1000W, this needs to be divided by 1000 to get the power in kW.
Many online calculators can do this math for you.
When do you use kW?
Paying for electricity means paying for kilowatt-hours consumed, in other words for power used over some time.
Therefore, if you want to know how much electricity is used by a device, or how much you’ll have to pay for it, you will use kW.
If you want to know the total energy consumed by multiple devices, you just add up their consumption in kilowatts.
When do you use VA?
When you are buying and replacing wires, loads and fuses for your equipment, you need to specify them in VA.
This is because, unlike real power, apparent power (that is measured in VA) takes into account peak voltage and peak amperage, no matter if they’re in phase or not, and you want to make sure that your equipment will be well supplied.
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