A Buyer's Guide To Heaters: 120V vs. 240V

By Shakir Williams on 08/09/2017

stelpro heaters

Winter is approaching, so it's time to start thinking about updating the electric heaters in your home or business. Whether you are updating one or two heaters in your home, or you are renovating a commercial space and installing new heat options, you will need to know how much voltage, amperage, and wattage the circuit can handle.

Where Can I Locate The Voltage Of My Existing Heater?

You can find the voltage of your heater on the product's label. If you are not able to locate the voltage from the product label, you can check the circuit breaker to figure out the voltage.


To determine what your space can handle, start by examining your electrical breaker panel. Electrical circuit breakers should have amperage marked on the toggle handle or on the top part of the module. Generally, a 240-volt circuit breaker will have a double pole due to the large supply of energy that is needed to power the heater. A 120-volt will normally have a single pole.


(Single Pole (left) vs. Double Pole (right) Circuit Breaker)

Volts AC Size of Breaker or Fuse Wire Size Max. Wattage Allowed
120V 20 AMP Single Pole 12/2 Ground 1920
240V 20 AMP Double Pole 12/2 Ground 3840
240V 30 AMP Double Pole 10/2 Ground 5760

What If My Breaker Doesn't Look Like The Pictures Above?

That's not a problem! Some circuit breakers will look a little different. In those cases, you will need to use a voltmeter to test the power coming to the heater. This will require caution, if doing it yourself, because you'll be testing live wires. It is suggested that you contact a licensed electrician when dealing with hazardous electrical wires.

You should never assume that you know the voltage amount without checking. Hooking up the wrong voltage heater can be dangerous! If you are unfamiliar or uncomfortable with electrical wiring, please contact a qualifie technician or licensed electrician.

120V or 240V Electric Heater?

If you are replacing your current heater with a new one, you want to make sure to match the power supply that you already have, If you are adding anew heater, 240 voltage heaters are recommended, because they have the capability to support more wattage.

However, hooking up the wrong voltage heater to the wrong circuit will cause you to only receive 25% of the wattage it was designed to deliver.

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