Lets firstly understand the symbols and what they represent.

  • KVA is Apparent Power available.
  • kW is Actual Power available.
  • PF is the ratio of working power, measured in kilowatts (kW), to apparent power, measured in kilovolt amperes (kVA)
    • Electrical Efficiency.
      • PF @ Unity is 1kVA = 1kW, this is perfection with no losses
      • PF @ 0.8 as universally agreed as a standard is 1kVA = 0.8kW

kW is the unit of real power and kVA is a unit of apparent power (or real power plus re-active power)

To expand on it a bit more, the kW rating is essentially the resulting power output a generator can supply based on the horsepower of an engine.

kW is figured by the horsepower rating of the engine times . 745.

The engine output is the limiting force in all generators

A generator in theory will keep delivering power until it stalls, or over reached its kW limit.

When sizing a genset you really need to know the load in kW, kW is the actual power not kVA.

In Australia many sellers of generators talk in kVA at a Power factor rating of 0.8 (See below), this allows them to kind of overstate the size of the genset

We call this industry standard. Are they wrong? No, Are they correct? No,

it’s all based on math’s and an assumption of a 0.8pf.

This in itself can lead to potential clients purchasing a generator that will not deliver on the clients needs – this is important

Understand how much power you need in Watts or kW as this is the true state of required power.


The kW to kVA Formula:

Ok here we go.



The formula for converting kW into kVA, this is important please understand.


  • Actual power (kW) / power factor (pf) = apparent power (kVA)


So if I have a 10kW alternator driven by an engine rated for the purpose @ 0.8pf

10kW alternator

Divided by PF 0.8


Therefore the generator would be classed as either 10kW or 12.5kVA

Using pf of 0.8 the above is called a 12.5kVA generator

Using pf unity the above would be a 10kVA generator

kVA and pf are the varying factors, but the actual power stays the same at 10kW.

Even though kVA is stated I believe kW should also be quoted.


Share this post: