How to Choose a Generator

  1. Determine which devices need to be powered simultaneously and record the Running Watt and Starting Watt requirements of the devices in the table below.

    Most electrical devices have a data tag attached that list volts, amps, phase, cycles and hp.

  2. Total the Running Watts column in the table below and record that number in box A. (Amps x Volts = Watts)

  3. Identify the device with the highest Starting Watt requirement and record that number in box B

    Toasters, lamps, and coffee makers are resistive; their total load can be calculated at Amps x Volts = Watts needed.

  4. Add the total Running Watts (A) and the highest Starting Watt value (B) to determine the total Starting Watts needed (C)

    Saws, compressors and drills are reactive; their starting load should be calculated at 3 x (Amps x Volts) = Watts needed.

Electrical Device Running Watts Starting Watts
Total of Running Watts Column
Highest Starting Watt Value
Total Starting Watts Needed

Running Watts

The power required to run an electrical device once it has been started. Also referred toa s "Continuous" or "Rated" watts.

Starting Watts

The power required to start an electrical device, often three times the running watts. ALso referred to as "Peak" or "Surge" watts.

Resistive Loads

An Electrical load in which voltage and current are converted to energy in the form of heat.

Reactive Loads

An electrical load that contains inductance or capacitance, either with or without resistance.

Volts (V)

The volt is the basic unit for electric potential. The higher the voltage, the greater the amount of electrical energy that can be transferred through a circuit.

Amps (A)

Amps are the amount of electricity or current flowing through a wire, similar to the flow of water through a pipe.

Phase (PH)

A single-phase alternating current system has a single voltage in which reversals occure at the same time and are of the same alternating polarity through the system.

Horespower (HP)

A common measurement of engine power. One horsepower is basically the power needed to lift 550 pounds one foot off the ground in exactly one second.

Cycles (Hz)

An international measure of frequency or vibration equal to 1 cycle per second. The alternative current frequency used in North America is 60 hertz.