You’ve probably done it. Most of us have. You’re sitting on the couch, your phone charger won't reach the outlet, so you grab that old orange extension cord from the garage and daisy-chain it right into the power strip behind the TV. It works. The phone starts charging. You don't smell smoke, so you assume everything is fine.
But it isn't.
In the world of electrical safety, plugging an extension cord into a power strip—or vice versa—is known as daisy-chaining. It’s also a direct violation of the National Electrical Code (NEC) and Occupational Safety and Health Administration (OSHA) regulations. More importantly, it is a leading cause of house fires that people simply don't see coming until the drywall is melting.
The physics of why daisy-chaining fails
Electricity isn't magic. It’s a flow of electrons that generates heat based on resistance. When you plug an extension cord into a power strip, you are fundamentally altering the resistance levels the original wall outlet was designed to handle.
Most people think of power strips as "extra outlets." They aren't. They are temporary physical expansions of a single duplex wall outlet. That wall outlet is usually rated for 15 or 20 amps. When you add a power strip, you're still pulling from that same 15-amp limit. Now, when you add an extension cord into that mix, you’re adding length.
Length equals resistance.
As the cord gets longer, the voltage drops. To compensate for that voltage drop, the device at the end of the cord tries to pull more current. This creates heat. If you’ve ever touched a power strip and felt it was "warm," you’re feeling the literal breakdown of the plastic insulation. It’s a ticking clock.
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The myth of the surge protector
We tend to use the terms "power strip" and "surge protector" interchangeably. They are not the same thing. A basic power strip is just a plastic box with a few extra sockets and a circuit breaker. A surge protector contains Metal Oxide Varistors (MOVs) designed to shunt excess voltage to the ground.
When you plug an extension cord into a power strip, you often bypass the safety mechanisms of the surge protector. The internal breaker on the strip is designed to trip when it hits a specific amperage, usually 15 amps. However, if you have a long, thin extension cord plugged into it, the resistance in that cord might prevent the strip from "sensing" a short circuit or an overload until it’s too late. The cord could literally melt and catch fire before the power strip ever decides to click off.
Real-world dangers you can't see
According to the National Fire Protection Association (NFPA), electrical distribution and lighting equipment are the leading causes of home fire property damage. A huge chunk of these fires starts because of "temporary wiring" used permanently.
Extension cords are intended for temporary use. They are not designed to be buried under rugs, stapled to baseboards, or plugged into other power taps. When you leave an extension cord plugged into a power strip for months at a time, you’re asking the copper wire inside to perform a job it wasn't manufactured for.
The gauge of the wire matters immensely. Most household extension cords are 16-gauge or 14-gauge. The lower the number, the thicker the wire. If you plug a thin 16-gauge cord into a power strip to run a space heater or a portable air conditioner, you are creating a high-heat scenario. The heater draws massive amounts of current. The thin wire of the extension cord struggles to deliver it. The connection point—where the cord meets the power strip—becomes a "hot spot."
Honestly, it's scary how fast a hot spot can ignite a nearby curtain or a pile of dust.
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What the experts actually say
If you ask a licensed electrician about plugging an extension cord into a power strip, they’ll give you a blunt answer: Don't. Groups like the Electrical Safety Foundation (ESFI) are very specific about this. They point out that power strips and surge protectors are "relocatable power taps." They are tested by laboratories like UL (Underwriters Laboratories) specifically to be plugged directly into a permanently installed wall outlet.
UL 1363 Standards
The UL 1363 standard is the benchmark for power strips. It specifically states that these devices should not be "series-connected." Doing so voids the UL listing. If a fire starts because you daisy-chained cords and strips, your insurance company might actually have grounds to deny the claim because you were using the equipment in a manner that violated its safety listing and local fire codes.
When you absolutely need more reach
Life happens. Sometimes the outlet is just too far away. If you find yourself reaching for an extension cord to bridge the gap to your power strip, you have a few safer alternatives.
First, look for a power strip with a longer cord. You can buy high-quality surge protectors with 15-foot or even 25-foot heavy-duty cords. This is one continuous piece of wire from the wall to the sockets, which eliminates the "junction heat" created by plugging two things together.
Second, consider the "gauge" of the equipment. If you must use an extension cord for a high-draw appliance (though you really shouldn't), it must be a heavy-duty, 12-gauge cord rated for the appliance's wattage. But even then, keep it plugged directly into the wall.
The space heater rule
Never, under any circumstances, plug a space heater into a power strip or an extension cord. Space heaters are the "heavy hitters" of home electricity. They pull nearly the maximum capacity of a standard household circuit. They need to be plugged directly into the wall. Plugging a space heater into a power strip—especially one that is already daisy-chained—is the fastest way to melt your carpet.
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Red flags to watch for
Maybe you have a setup like this right now and you're thinking, "Well, it’s been fine for three years." You might be lucky. Or you might be minutes away from a failure.
Look for these signs:
- Discoloration: If the plastic around the outlet on the power strip looks slightly yellow or brown, it’s been overheating.
- The Smell: Electrical fires often smell like fish or burning plastic long before you see flames.
- Warmth: Touch the cord. It should be room temperature. If it feels warm to the touch, it is overloaded.
- Buzzing: If you hear a faint sizzling or buzzing sound, that’s "arcing." It means electricity is literally jumping through the air because the connection is loose or damaged.
Actionable steps for a safer home
If your home or office is currently a web of tangled cords and interconnected strips, it's time for an audit. Electrical safety isn't about being paranoid; it's about respecting the sheer amount of energy moving through your walls.
Audit your cord situation today:
- Unplug all daisy-chained devices. If you have a strip plugged into a strip, or a cord into a strip, pull them apart.
- Check the wattage. Look at the back of your power strip. It will say something like "1875W." Add up the wattage of everything plugged into it. If the total is close to 1800, you are redlining that strip.
- Invest in "extra long" surge protectors. Stop trying to make a 3-foot cord reach 6 feet. Buy a strip with a 10-foot, 14-gauge cord.
- Install more outlets. If you constantly need extension cords, your house doesn't have enough outlets for modern life. Hiring an electrician to drop a new outlet box is cheaper than a fire deductible.
- Discard damaged cords. If a cord has a nick in the insulation or a bent prong, throw it away. Don't wrap it in electrical tape. Tape doesn't restore the structural integrity of the wire or the insulation's heat resistance.
Stop treating extension cords like permanent wiring. They are temporary solutions for temporary problems. For anything else, get a longer-corded surge protector or call an electrician to put an outlet where you actually need it.