Generator safety tips

Portable, gasoline-driven generators can be used to bring electricity to construction sites, recreational areas and other remote locations. Small appliances, lights and pumps can be plugged directly into outlets on portable generators.

Avoid hazards

Wisconsin Department of Health Services portable generator hazards

Use extension cords safely

Use only UL-listed, three-prong extension cords with generators. Plug the appliance into the extension cord first and then plug the extension cord into the generator outlet.

Avoid generator overload

Use the following table as a guide, or check owner manuals. Generators must be sized to handle starting wattages*, which are greater than running wattages.


Running wattage

Refrigerator or freezer 1,000
Central air conditioner Check nameplate
Window air conditioner Check nameplate
Gas furnace fan Check motor info
Motor: 1/4 HP 600
Motor: 1/3 HP 800
Motor: 1/2 HP 1000
Motor: 3/4 HP 1400
TV 100 to 500, depending on size/type
Microwave 800

* For motorized equipment, multiply running wattages by 2.5 for most items, such as furnace fans, or by 7 for well pumps, air compressors and air conditioners.

Other electrically powered equipment such as emergency medical devices, computers and sophisticated electronic equipment may require special backup or power conditioning equipment. Check your manual or with the manufacturer directly for more information.

Install transfer switch

Circuit box illustration

Transfer switch illustration

Used improperly, electric generators — even small, portable models — can threaten your safety and the safety of everyone around you, including our employees working on the electrical system.

Portable generators are not designed to be connected to your house or building wiring. Doing so can feed power back to electric lines. This is life-threatening for utility crews working to restore an outage and curious children seeing a power line on the ground. Improper installations also can damage the generator and any connected equipment and appliances.

The only safe way to connect a generator to your existing wiring is to have a licensed electrician install a transfer switch. A transfer switch isolates your circuits and prevents dangerous back feed. The transfer switch creates a safe path from your generator to your home circuits. Transfer switches are convenient. They allow you to operate appliances you typically could not power with a portable generator, including furnaces and well pumps. And you don’t need extension cords.