How to Determine Wattage for a Home Generator

A home generator is a perfect solution for supplying electricity to your home during power outages.
With a home generator you will still have lights, heating or cooling as well as save food in a refrigerator and freezer. There are many different sizes and models of home generators. When you have decided on the type of home generator, such as stand-alone or wired to the electrical panel, it is time to decide on the right size to meet the electrical demand of the appliances you will run during a power outage.

Step 1

Write down all of the electrical appliances that may be running at the same time during a power outage. For example, include lamps, radios, hair dryers, hot water heater, heater, air conditioner, television, computers and any other appliances that you might use during a power outage.

Step 2

Locate the watts used for each appliance. The watts may be listed on a tag on the cord, a label on the appliance or in the owner’s manual for the appliance. If the only measurement is amps, multiply the amps times the volts to determine the wattage. A regular outlet is 110 volts, a large outlet for a dryer or electric stove is 220 volts. If you cannot find this information, use an ammeter to measure the watts for each appliance.

Step 3

Consider the surge, or starting wattage for each appliance. Every appliance has an initially higher electricity draw during start-up. The starting surge might be twice the running watts for that appliance. Add this to the calculation for each appliance that could start up at the same time. Add the starting watts required for each appliance and divide by two since you will not typically start up more than half of the appliances at the same time.

Step 4

The total wattage needed for a home generator is one half of the starting surge plus the total wattage required for all of the appliances you need to use during a power outage.

Things You Will Need

  • Ammeter
  • Pen or pencil
  • Paper


  • Consider the placement for a portable generator. Place in a location where there will be easy access for extension cords to be run to the generator while creating minimal trip hazards in the home.


  • Only a qualified electrician should wire a home generator into an electrical panel. The risk of electrocution is extremely high and certain precautions must be taken to prevent the risk of death.

About the Author

Emily Patterson has been creating content for websites since 1996. She specializes in home improvement, natural body care and natural cleaning articles. Patterson holds a computing certificate from Penn State University.