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Can You Use an Extension Cord With a Space Heater? – Answered

Written by Edwin Jones / Fact checked by Andrew Wright

can you use an extension cord with a space heater

Space heaters help us get through winter by providing comfortably warm air at the click of a button. They plug directly into an outlet and use electricity without any additional components or issues. However, space heaters are not always used throughout the year, so some people prefer plugging them into extension cords for portability.

But can you use an extension cord with a space heater? We do not recommend this setup due to possible fires, especially if you do not know the wire rating of the extension cord. But if you really need to, use at least 14-gauge or thicker extension cords until you have installed a permanent outlet for the space heater.

Why Shouldn’t You Use an Extension Cord With a Space Heater?


Space heaters use a lot of current. Normally, they go beyond the maximum amount a 12-amp circuit can supply – 1500 watts. This is true for most heaters, even with portable heaters rated for small rooms.

Sadly, common extension cords are not suitable for high continuous loads. Cheap extension cables use 16-gauge wires that often have a lower rating, and these extension cords get hot when used with a space heater.

If you plug a space heater into an extension cord, the insulation of the latter can melt and ignite. If the setup is near flammable items like rugs, carpets, or curtains, it can cause a fire. Some apartment fires can even be traced to cases when a space heater melted extension cord and ignited the mattress.

What’s worse is that some people plug multiple appliances into their power strips and not just have a small space heater go into an extension cord. This is very dangerous since the wire runs a risk of overloading and further increases the risk of fire.

What Happens if I Use an Extension Cord With a Space Heater?


Current flowing through any conducting wire may generate heat due to the wire’s resistance. The more current flows through a wire and the greater the resistance of the wire, the greater the heat generated.

Electric wires are rated based on the maximum capacity they can deliver. Usually, a 16-gauge wire is rated for 13 amps; 14-gauge wire for 15 amps; and 12-gauge wire for 20 amps. However, continuous loads (like a space heater) must only use up to 80% of the circuit’s capacity to serve as an allowance for electric hazards.

The maximum power rating for 16-gauge wire is 1625 watts, which means it can only safely handle 1300 watts (80% of 1625 watts). This is lower than the 1500-watt requirement of the space heater, and the wire starts getting pretty hot when it’s close to its 1625-watt limit.

If the space heater remains plugged for a long time, it can cause the extension wire to ignite.

 Read more: Ideal Extension Cord Gauge for a Space Heater.

Do’s and Don’ts of Space Heaters

1. Plug the space heater directly into an outlet when you can.


Because space heaters will use lots of energy, it’s best to plug them directly into an outlet. Fires have been reported on the use of space heaters plugged into extension cords. Try to install an outlet close to your high-load appliances when you can.

2. Do not plug a space heater into an extension cord if you do not know the extension cord’s rating.

If you are unsure if the type of extension cord you have can handle your 1500-watt space heater, don’t use it. Just plug the space heater into an outlet.

3. Do keep the extension cord and electronics away from moisture. Install fire alarms and fire extinguishers as well.


4. Do not use heaters with broken plugs or wires. Do pick models that turn themselves off when there’s excess heat.

Safety Tips for Using an Extension Cord With a Space Heater


If you really need an extension cord for space heater, make sure that you consider the following points. Remember, the wrong extension cord can cause a fire and cost you a fortune:

1. Use at least 14-gauge wires.

We previously talked about 16-gauge wires and how they are not suitable for space heaters. If you are looking for a 1500-watt space heater extension cord, consider 14-gauge or thicker. 14-gauge is the wire size used for 15-amp circuits at home and can safely handle up to 1500 watts of continuous loads.

You can go thicker if you want and choose a 12-gauge extension cord, which is suitable for 20-amp circuits. You surely will not have a problem if you go for a 10 gauge extension cord for space heater, but it may be more expensive.

2. Use UL-certified extension cords.

Extension cords can be deceiving. Even a heavy-duty extension cord that is made with cheap materials can be dangerous to use with space heaters. Make sure that you use cables certified by Underwriter Laboratories (UL) to ensure that they meet safety standards.

3. The space heater should be the only appliance on the extension cord.


Space heaters can draw a lot of electricity, so using one space heater is already a lot for one extension cord to handle. If you plug more appliances into the extension strip and run them simultaneously, the extension cord might overheat and cause a fire.

4. Do not place extension cords near flammable materials.

Do not run extension cords under carpets nor place them near curtains or other flammable materials. The fire might get out of hand when the extension cord starts igniting nearby items.

5. Use portable cords with built-in safety features.

If you use an extension cord for 1500 watt heater, use the one with built-in safety features like circuit breakers or fuses. These are additional safety measures to prevent overloading your extension cord. They are also becoming quite common these days.

6. Use only the length you need.


Do not use an extension cord that is too long. A lot of us coil up the wire if it is too extensive. This causes the center of the coiled-up wire to be hotter due to the lack of air flow and makes it easier for the extension cord to combust.

Frequently Asked Questions


Can I plug a space heater into a power strip?

Though we strongly advise that you do not plug a space heater into any portable cord, you can plug a space heater into a power strip. Just make sure to follow our safety tips listed above for using extension cords with space heaters.

What size extension for a 1500-watt heater?

Go for a 14-gauge extension cord. Make sure that the length is only long enough for your needs with no need to coil up the excess.


Space heaters are best plugged directly into a wall outlet. These power-hungry appliances will draw a lot of electricity and can overwhelm cheap extension cords.

But if you are wondering, “Can you use an extension cord with a space heater?”, you can. Since a lot of cheap extension cords are out there, we strongly advise against this practice, but if you know the rating of the extension cord, you can safely decide to use it until you can safely bring the space heater closer to an outlet.

Related: What Happens If I Plug a Space Heater into a Surge Protector?

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