Generators’ power is rated in kilowatts (kW), which is a measure of 1,000 watts. In a generator’s specifications, you will often also see measurements of kWm and kWe. These are both measures of power. What differentiates them is the type of power being measured: mechanical and electrical, respectively.
A kWm is 1,000 watts of mechanical power. This type of power is generated from fuel by mechanical processes, such as the ones that occur in your genset’s engine or a turbine. Then, the mechanical power is sent to the alternator, where it is converted into an electrical form, measured in kWe.
A kWe is 1,000 watts of electrical power, which is generated by a genset’s alternator from the mechanical energy of the motor. It is this electrical energy that powers your home or business.
The conversion from kWm (input) to kWe (output) is not exact due to the power required by the genset’s components, as well as inefficiencies lost to heat. This lost power can be measured in thermal kilowatts. With this in mind, rated kWe of a genset will always be less than kWm. The exact ratio of kWm to kWe is determined by the efficiency of your specific generator.
Kilowatts to Horsepower
Another common measurement of generators’ power is horsepower, or hp. To determine one measurement using the other, rely on the formula kilowatts = mechanical horsepower × 0.7457.