Can You Plug a Space Heater into an Extension Cord?

Anyone who has ever bought a space heater and bothered to look at the user’s manual has probably read that they’re not to use an extension cord. 

And yet people still ask whether they can plug a space heater into an extension cord.

So, can you plug a space heater into an extension cord?

The answers are no and maybe.

Why You Shouldn’t Plug a Space Heater into an Extension Cord

Manufacturers state DO NOT plug your heater into an extension cord, surge protector/power strips, GFCI outlets, smart plugs, or anything other than a wall outlet.

Most space heaters use about 1,500 watts or 12.5 amps of power. 

And most homes in North America have a combination of 15-amp and 20-amp circuits. 

If you need clarification on what your home has, look at your breakers or fuses; they should say either 15 or 20.

Why are those numbers important?

In most cases, overloading the circuit will cause your breaker or fuse to trip or burn out. 

And running a space heater using 1,500 watts or 12.5 amps while running something else on the same circuit will cause an overload. 

Particularly on a 15-amp circuit.

Tripping a breaker or blowing a fuse occasionally isn’t that dangerous because that’s what they’re designed to do. 

Eventually, though, overloading the circuit could cause your wiring to overheat, which could melt the insulation around your wiring and potentially lead to a fire.

Extension cords pose a similar danger.

Extension Cord Basics

Extension cords are made for various uses, and it’s essential only to use a cord designed for a specific application. 

So just using any extension cord lying around your home for your space heater is a bad idea.

There are three aspects to extension cords that come into play.

  • Gauge
  • Rating
  • Amps

Gauge. American Wire Gauge (AWG) is a measurement of the diameter of the conductors in any given cord. 

And the larger the number, the smaller the gauge.

The thinner extension cords you would commonly use in your home are 16-gauge. 

You could use this cord to plug in any appliance that draws minimal amperage, volts, or watts. 

For example:

  • Alarm clocks
  • Floor lamps
  • Portable table fans
  • Table lamps

The highest gauge is 10, and extension cords in this gauge would be used for things like:

  • Compressors
  • Generators
  • Heavy machinery
  • Lawnmowers
  • Tile saws

There are 10, 12, 14, and 16-gauge extension cords.

Another vital factor is voltage drops. 

The larger the gauge—remember, the largest gauge has the smallest number—the better a cord can carry power over a distance. 

The longer the cord, the more voltage will drop over the distance.

A low gauge extension cord won’t have sufficient voltage to run a space heater and can cause permanent damage, including fires.

Amps, Volts, and Watts. Amps is a measurement of the electrical current running through the extension cord. The higher the number, the higher the current.

Voltage measures the force that pushes the electricity. 

The higher the force, the higher the voltage.

Wattage is the measurement of electricity used.

Every extension cord has a rating on how many amps or watts it can safely manage. 

Trying to run your space heater with an undersized electrical cord can cause it to overheat and cause a fire.

Rating. All extension cords are clearly rated for what they should be used for:

  • Light duty 
  • Medium duty
  • Heavy duty

Each of those ratings may be further broken down. 

For example, there’s a 16/2 light-duty extension cord and a 16/3 light-duty extension cord.

When is it Okay to Plug a Space Heater into an Extension Cord?

Now that you’ve been through a beginner’s guide to extension cords, are you starting to see the light? 

From that lamp, you have plugged into a 16-gauge extension cord?

Where do space heaters fall if things like table lamps are plugged into thin extension cords, and stuff like generators are plugged into the thickest of extension cords?

You shouldn’t need a 16-gauge cord to run a space heater that uses 1,500 watts or 12.5 amps. 

Many heavy-duty extension cords are safe with tools and appliances that use up to 30 amps or 3,750 watts.

If you must use an extension cord with your space heater, make sure you use one that is at least 14-gauge. 

So that means you can use a 14-gauge extension cord or a 16-gauge. 

Using a 10 or 12-gauge extension cord increases the potential of fire.

Having said that, if the warranty of your space heater is a concern, don’t do anything that will void it. 

In many cases, this will include plugging your space heater into anything other than a wall outlet.

Space Heater Safety Tips

Are there any other concerns when using a space heater?

Yes. 

There are hazards that you should be aware of. 

According to the National Safety Council, cooking is the number one cause of house fires in the US, with heating coming in second.

With that in mind, consider the following.

  • Always place your space heaters on a hard, nonflammable, level surface. Check the manual, as many manufacturers don’t recommend putting them on a table.
  • A minimum distance of 3 feet should be kept from children and pets.
  • Additionally, a minimum of 3 feet from combustible materials, such as drapery, bedding, and furniture, should be maintained. Many taller heaters require further distance.
  • Never place a space heater where paint, gas cans, or flammable items are stored.
  • Never sleep with a space heater running in your room; always turn them off before leaving home. Essentially, don’t leave a space heater unattended.
  • If you don’t already, have smoke alarms and CO detectors on every level of your home and test them regularly.
  • Consider safety features such as tip-over switches, automatic shut-off, or overheat protection.

Can You Plug a Space Heater into an Extension Cord? Conclusion

If in doubt, don’t do it when plugging your space heater into an extension cord.

Keep in mind that many manufacturers will void your warranty if you plug your heater into anything other than a wall outlet.

However, if you must use an extension cord, use one with the correct rating, amperage, and gauge.