How to Use the 240/120 Volt Receptacle on a Generator

Portable generators with 120/240V capability typically include a four-prong electrical receptacle for powering 240V appliances, as well as multiple 3-prong receptacles that supply 120V power.
Using the 120/240V receptacle requires changing a control switch from 120V-Only power to 120/240V power. When 240V power is not needed, the switch should remain in the 120V-Only position and the 120/240V receptacle should not be used.

Step 1

Turn off the generator if it is running. Unplug all appliance cords from the generator's receptacles, or make sure all plugged-in appliances are turned off. Starting the generator with appliances plugged in and switched on (applying electrical loads) can damage the generator.

Step 2

Set the generator's voltage selector switch to the 120/240V position to use the 120/240V receptacle.

Step 3

Start the generator. Confirm that all indicator lights report normal operation.

Step 4

Plug your appliance's 4-prong cord into the 120/240V receptacle to supply power to the appliance. Turn on the appliance, as applicable.

Step 5

When the 120/240V receptacle is not needed, turn off the generator and turn off all appliances plugged into the generator, or unplug the appliances. Always remove the plug from the 120/240V receptacle if the appliance is not in use. Switch the voltage selector switch to the 120V-Only position. Do not use the 120/240V receptacle when the switch is in the 120V-Only position.


  • You can use the 120V receptacles at the same time you're using the 120/240V receptacle, but it's important to balance the loads to prevent overloading a circuit. Generators with 120/240V capability have two circuits. In 120V-Only mode, the two circuits share the load of all 120V receptacles. But in the 120/240V mode, the two circuits are split among the receptacles and are more susceptible to overloading. If you're using multiple receptacles while in the 120/240V mode, balance the load by choosing receptacles on different circuits. For help, consult your owners manual or contact the manufacturer.

About the Author

Jonathan Stewart began writing with an op-ed in the "Jackson Sun" in 2006. He writes for multiple websites and is a frequent contributor to regional newspapers. He is currently a student at Northeast Mississippi Community College, Booneville.