An Electrician Warns: Never Plug AC Units or These Other 6 Devices Into Extension Cords

CNET

07-08-2025

With scorching temperatures rolling across the Northeast and Midwest, many have been running their AC units nonstop to combat the heat. If you have a window unit, you may be tempted to use an extension cord to get it into your window, but that could be dangerous. Air conditioning units and a variety of other household devices should never be connected to extension cords -- and that warning goes for power strips and surge protectors as well.
It might seem like a harmless shortcut, especially if wall outlets are limited, but doing so creates a safety hazard, according to Paul Martinez, owner of Electrified NYC in Brooklyn.
"No extension cords whatsoever," Martinez says, referring to devices that run constantly or appliances with a heating element. If you're not sure which devices and appliances shouldn't be plugged into extension cords, here are seven of the most important ones to remember.
Read more: Best Surge Protector
1. Air fryers
Air fryers are great for quickly cooking and warming food, including full meals and side dishes, but it's not a good idea to attach them to extension cords or power strips. Although they range in wattage based on size, large air fryers can draw up to 2,000 watts, making them a major fire hazard if they're attached to an extension cord. If you don't have counter space to keep your air fryer out full time, it's best to only pull it out when needed and plug it into a dedicated wall outlet every time.
2. Microwaves
Many homes have a built-in microwave, but not everyone has this feature. If you have to find a place to connect yours in your kitchen, this is another heavy-duty appliance that should live on its own dedicated circuit because of its high wattage.
3. Extension cords
Plugging extension cords into other extension cords is another huge "no" in the electrical world. This practice, called "daisy chaining," can lead to the circuit overheating, which would cause the cords to overheat and lead to a fire.
Extension cords should never be plugged in to each other.4. Space heaters
Electric space heaters have long been known to be a major cause of fires. The Consumer Product Safety Commission estimated that between 2017 and 2019, portable space heaters were involved in 1,700 fires per year, with some of those fires resulting in deaths.
"Let's say you connect [an extension cord] to a floor heater," Martinez says, "the plug melts and it starts a fire. That's why you can't use extension cords and/or power strips for any appliances, because they should be used for electronics only."
Read more: Never Put a Space Heater in These 9 Places
5. Toasters and toaster ovens
Although toasters are smaller kitchen appliances, they use a lot of energy and can also pose a fire threat if connected to an extension cord or power strip. Toaster ovens need even more power to operate, with wattage ranging from 1,200 to 1,400 watts.
"A lot of people don't have knowledge of extension cords," says Martinez. "If extension cords are 14-gauge and you're running an appliance with a heating element, (like) a toaster oven, microwave or dishwasher, a 14-gauge will not hold the amperage and can burn up the extension cord. And that's what causes fires in New York City."
Fourteen-gauge and 12-gauge extension cords are some of the most common extension cords. A 14-gauge cord can handle up to 1,800 watts, or 15 amps, the same as a standard wall outlet in the US. But Martinez recommends that any appliance using more than 1,500 watts should always be on a dedicated circuit.6. Refrigerators
While refrigerators use less power -- about 300 to 800 watts -- than some other kitchen appliances, they're still not recommended for extension cord use because they are constantly running. Even if an extension cord doesn't cause a fire when attached to a fridge, there's a possibility the connection could cause the fridge to malfunction.
While they are not as high-powered as the other kitchen devices, you should still avoid plugging refrigerators into extension cords.7. Air conditioning units
AC units use a lot of power to keep your home cool, so they need to be plugged into a wall outlet as well. Martinez stresses the importance of purchasing the correct AC unit for your space. You can use an online BTU calculator to calculate the type you will need to effectively cool your space.
"People just buy a 5,000 BTU air conditioner, because it's $99 on sale, and they think it's going to cool off (their home), and it does not," according to Martinez. AC units "are supposed to cycle on and off, so they don't pull that much energy. So if you undersize it, the compressor is going to work 10 times harder." This can result in your home never properly cooling off, a higher electricity bill, and if the unit is connected to an extension cord, possibly a fire.
It is important to determine what size air conditioner unit you need based on the size of the area you are trying to cool off.
James Martin/CNET
The bottom line on extension cords
Martinez says the big thing to keep in mind regarding extension cords is to never use them with any "appliances whatsoever." He also says that your average home extension cords shouldn't be used for anything above 15 amps (1,800 watts), regardless of where or how the device operates. When it comes to power strips and surge protectors, those should only be paired with electronics.
For more home tips, here's how to defend against porch pirates and here's how to purify your air with houseplants.