What is the Difference Between 120V and 240V?

What is the Difference Between 120V and 240V?

            Electricity in general can be a confusing and intimidating subject. One very common point of confusion is the difference between 120V and 240V, and how to determine what voltage type to use for various situations. In this article we’ll cover these basic differences, and the appropriate situations to use these common voltage types.

What is my Homes Voltage?

            The voltage coming into a US home breaker box from the power company is a 240V (3) wire connection, and the 3 wires consist of (2) 120V hot lines and a neutral line. The homes breaker box will then separate the circuits between the 240V connection into the appropriate 120V only (single 120V hot line) circuits and the appropriate 240V only (two 120V hot lines) circuits. Most of the standard outlets in an average US home will be 3 prong 120V outlets like a standard wall outlet, and some appliances in an average US home might be 240V, common examples include most water heaters, central AC units, electric stoves, and electric washers and dryers. In most cases a 3-prong outlet is 120V and a 4-prong outlet is 240V, but there are some exceptions where certain configurations of 240V might have a 3-prong outlet as well; and because of this you should always verify that you’re using the correct voltage by checking the markings on the outlet and the labeled electrical requirements of the product getting plugged in.

To help verify your devices voltage requirements we recommend looking into the manual or on the device itself for power input requirements. The power input requirements will let you know the voltage needed to power your items safely. The common United States voltages you can expect for devices requiring 120V will have a label showing a voltage between 110V and 125V; and the voltages you can expect for devices requiring 240V will have a label between 220V and 250V; please note that the reason for the varying number sets are due to the National Electrical Manufacturers Association (NEMA) allows a voltage variance of plus or minus 10% or less.

Other Voltage Types

There are many other variations of voltages that you might encounter and aren’t common to households. For example, industrial buildings will commonly use 3-phase power and can have voltages between 120V and 480V, but a 120V 3-phase power line would be much different than the standard single-phase 120V power line you’ll find in your home; so, you wouldn’t be able to run 120V 3-phase industrial equipment in your home without causing damage to the equipment or home circuits. Another example of voltage variation you might encounter is most international versions of 220V-240V depending on the country, which is also a different form of power compared to the standard US 240V output; this would be due to the US 240V power being built with (2) 120V hot wires with a neutral, rather than the common international 240V power having a single 220V-240V hot wire, and neutral, and you’d need to obtain a power converter to use standard US electrical products overseas.


While there’s still a lot to learn about electricity, hopefully this article helped shed some light on the differences between voltage types. We here at DuroMax pride ourselves on offering quality generators that are capable of outputting both standard 120V and 240V single-phase power to help accommodate all your household voltage needs. If you have any further questions about electricity or would like to hear more about the generators we offer, please feel free to contact us at 844-DUROMAX.