120V Only or 120/240V: Outlets on a Generator

What the two voltage labels say on a listing

The voltage label is one of the first feature words on a generator listing. '120V only' means every outlet on the generator supplies 120 volts, the voltage of a standard US household receptacle. '120/240V' means the generator also has a dedicated 240 volt outlet for appliances that run on both hot legs of a 240V circuit.

The label appears in the listing title and in the bullet list. A title that names '120/240V' states both voltage sides: the 120V receptacles for standard plugs and the 240V receptacle for a larger plug shape. A title that names only '120V' tells you the generator is single-voltage.

Read the voltage label together with the outlet types guide, which explains the receptacle names that accompany each voltage. The 120V versus 240V article covers the electrical difference between the two sides.

Why 240V outlets matter for home appliances

Some home appliances are wired for 240V only. Electric dryers, electric ranges, water heaters, and some well pumps and central air conditioners use a plug that does not fit a 120V receptacle. If that equipment is part of your outage plan, a 120V only generator cannot feed those plugs directly.

A 120/240V generator provides the receptacle those plugs fit. Whether the generator also has enough output for the appliance is a separate question, answered by the starting and running watt figures on the listing and by the maker, not by the voltage label alone.

Matching a generator to a home's appliances is a question for the maker and a licensed electrician. The running watts versus starting watts article explains the two figures a listing names, and the home backup sizing article describes the questions to ask.

RVs, travel trailers and the 120V question

RV power inlets and campground pedestals are 120V. A travel trailer with a 30 amp inlet uses a TT-30 plug; a motorhome with a 50 amp inlet uses a larger plug. Both are 120V receptacles, so the 120V side of any generator is the side that feeds an RV.

A 120V only generator with an RV ready outlet can power the rig's 120V loads. A 120/240V generator can also power a 120V RV, through its standard receptacles or with a cord that matches the rig's inlet. The RV manufacturer's spec sheet states which inlet your rig has and what its loads need.

The RV requirements article and the 30 amp versus 50 amp outlet article cover the plug shapes an RV uses. The 120V versus 240V for RV article addresses the same question from the RV side.

Reading the outlet set on a listing

Listings name the outlet set in the bullet list and sometimes in the title. Common words include '120V only,' '120/240V,' '30 amp RV outlet,' '50 amp outlet,' 'L14-30' and 'TT-30.' These names identify plug shapes, not output, and each name corresponds to a voltage.

The maker's page lists every receptacle and the voltage it supplies. Compare that list to the plugs on your appliances and the power cord on your RV before you buy.

The outlet names on a listing are a shorthand for a receptacle standard. If a name is unfamiliar, look it up in the outlet types guide rather than guessing from the watt figures.

Voltage, wattage and generator type

The watt figures on a listing, starting watts and running watts, describe the generator's output. The voltage label describes the receptacle shapes where that output appears. A 120/240V generator feeds both its 120V outlets and its 240V outlet from the same output; the listing's watt figures apply across the outlet set.

Inverter generators and open-frame portable generators both come in 120V only and 120/240V forms. The type word on a listing does not decide the voltage; read both labels.

The inverter versus open frame article separates the type question from the outlet question, and the portable versus inverter article compares the two categories in listing terms.

When a listing does not name a voltage

Some listings omit the voltage label or name only the outlet count. A missing voltage is not a detail the catalogue fills in; it is a question to raise with the maker.

The maker's page and manual state the voltage of each outlet. If the listing and the maker's page disagree, trust the maker's page and ask before buying.

Questions to ask before buying

Before comparing listings, ask what voltage each appliance needs. The plug shape on the appliance or the RV inlet answers this; the appliance maker's spec sheet confirms it.

Ask the generator maker directly if the listing does not state the outlet set. The maker's manual and spec page are the authority on what each outlet supplies.

Generators burn fuel and produce carbon monoxide; read the CPSC's generator safety guidance and follow the maker's manual before you run any generator.

What to pick for your situation

Questions

Is a 120V only generator enough for a travel trailer?

Most travel trailer loads are 120V. The rig's inlet decides the plug shape, and the RV manufacturer's spec sheet states what the trailer needs. A 120V only generator with the matching outlet will feed those 120V loads.

Can a 120/240V generator power a 120V RV outlet?

Yes, through the standard 120V receptacles or with a cord that matches the rig's inlet. The 240V outlet is an additional receptacle; the 120V side still supplies standard household voltage.

What home appliances use 240V plugs?

Electric dryers, ranges, water heaters and some well pumps and central air conditioners are common 240V loads. Check the plug on each appliance and its spec sheet to confirm the voltage it needs.

Do inverter generators come in 120/240V forms?

Yes. The inverter label describes the generator's output method, not its voltage. Read the voltage label and the outlet list on the listing and the maker's page.

What does the second figure in 120/240V mean?

It names the higher voltage side of the outlet set. The generator supplies 120V at the household receptacles and 240V at a dedicated receptacle with a matching plug shape.