Determining an emergency generator’s required size involves totalling the wattage needed for each appliance to run in the event of an outage. The more appliances running during an outage, the higher the generator size required.
Finding the total wattage involves listing all appliances that require powering during an outage, including refrigerators, furnaces, and ejector, lift, sump or well pumps. The wattage on appliance nameplates and documentation is available in units of volt-amps, kilowatts or watts. The power requirement of an appliance is the multiplication of voltage by amperes for appliances that do not list this information.
Manufacturers are in a position to offer information on the starting power requirements for appliances with motors that do not have the information listed on their nameplates. The running power requirements for appliances without differing starting and running loads should also be taken into consideration.
Homeowners should choose generators that offer the option of running 240 or 120 volts. The standby generators should accommodate voltage and total power requirements for running all appliances selected.
For applications in which computers are required, it is advisable to select generators that offer 30 percent more power than required. This helps avoid signal distortions associated with some appliances as they run off generators.