Extension cords look harmless.
Cheap. Flexible. Convenient. Everywhere.
You can buy them in the checkout aisle for a couple of euros next to chewing gum.
But here’s the uncomfortable engineering truth:
Extension cords are one of the most common — and most ignored — electrical fire hazards in homes, offices, garages, and workshops.
They overheat quietly.
They hide faults invisibly.
They burn from the inside out.
And most people have absolutely no idea how easily a “simple extension cord” can kill power tools, fry appliances, start fires, or shock someone.
Today we take the gloves off and break down the dangers of extension cords — and why engineers hate the way people use them.
⚡ The First Big Truth: Extension Cords Are NOT Meant for Continuous High Load
Most people think an extension cord with a label like “16A” means:
“I can run anything up to 16A through this cord without worry.”
Nope.
That number assumes:
- perfect conditions
- full cord uncoiled
- no heat buildup
- no voltage drop issues
- no under-rated outlets
- no outdoor moisture
- short length
- high-quality copper
Reality is not perfect.
Your garage, basement, or garden definitely isn’t.
A 16A cord might be safe for a few minutes…
but under continuous load?
It can heat up 20–40°C above ambient, especially when coiled.
And heat = resistance = more heat = melting insulation = fire.
⚡ The Hidden Killer: Coiled Extension Cords
Every year, thousands of fires start because someone:
- used a cord without unrolling it
- left a power reel half-coiled
- buried an extension cord under a carpet
- tied a cord into a loop
Here’s the physics:
Coiled cables trap heat.
Copper resistively heats under load.
Normally, this heat escapes into the air.
But when coiled?
- airflow drops to near zero
- heat builds exponentially
- insulation softens
- melting begins
- layers fuse
- short circuit
- flames
A fully coiled cord running a heater, pressure washer, or compressor is a literal fire starter.
If you ever hear a reel making a faint “crackling” sound…
it’s cooking itself.
⚡ Reason #2: Voltage Drop in Long Cords Is Way Worse Than People Realize
Extension cords aren’t designed to maintain voltage integrity over long distances.
Even a “thick” extension cord has significant resistance.
10m, 20m, 30m cords introduce enough voltage drop to:
- overheat motors
- damage appliances
- stall compressors
- burn out power tool windings
- trigger brown-out failures
- make heaters pull more current
- cause dimming and flickering
Example:
A pressure washer pulling 12A at the end of a 25m cord can experience:
- 5–12% voltage drop
- massive starting surges
- motor overheating
- premature failure
That’s why power tools die “mysteriously” when used with long cords.
It’s not the tool’s fault — it’s the cord killing it slowly.
⚡ Reason #3: Most Extension Cords Use Cheap Copper… or Not Copper at All
Cheap cords from bargain stores often contain:
- copper-clad aluminum (CCA)
- thin strands pretending to be thick
- recycled copper with impurities
- undersized conductors
CCA looks like copper but behaves like:
- higher resistance
- lower current capacity
- lower melting point
- easier oxidation
- faster failure
Manufacturers use CCA because it’s inexpensive.
Consumers buy it because it looks the same.
Your “16A rated” cord?
Might handle only 8–10A safely.
⚡ Reason #4: Extension Cord Ratings Are Based on Unrealistic Lab Conditions
The rating assumes:
- 20°C ambient temperature
- full cord uncoiled
- perfect dissipation
- lab-grade outlet contacts
- short-term testing
- no harmonic loads
In real usage:
- garages hit 35°C
- attics hit 50°C
- outdoor sun warms cables to 60°C
- people run cords under rugs
- outlets have worn contacts
- devices draw spiky current
The difference between lab rating and real-world safe current can be 50% or more.
⚡ Reason #5: Extension Cords Are Not Designed for Permanent Use
Engineers design them for:
- temporary power
- mobile loads
- short-term usage
- low exposure to the environment
But people treat them like:
- permanent wiring
- ceiling wiring
- garage distribution
- workshop feeders
- outdoor power backbone
When used permanently, cords suffer:
- insulation wear
- UV degradation
- mechanical stress
- moisture intrusion
- rodent damage
- cracking
- pinching
Cords aren’t ruggedized cables.
They’re quick fixes — not long-term solutions.
⚡ Reason #6: Plug and Socket Connections Are Weak Points
Every plug/socket interface adds:
- contact resistance
- potential for arcing
- heat points
- mechanical looseness
- oxidation
- dust accumulation
When current flows through a loose or corroded connection:
- heat develops
- plastic softens
- contact springs weaken
- surfaces degrade
- arcing starts
- connectors melt
This is why extension cords often fail at the plug, not in the middle.
A melted plug is a symptom of contact failure, not a freak accident.
⚡ Reason #7: Outdoor Extension Cords Are Misused Indoors — and Vice Versa
Outdoor-rated cords:
- are thick
- heavy
- UV-resistant
- moisture-resistant
- tougher sheath
Indoor cords:
- thin
- light
- not UV rated
- not moisture rated
- not meant for temperature swings
Yet people constantly:
- use indoor cords on lawnmowers
- run indoor cords outdoors for months
- bury indoor cords in garden soil
- run outdoor cords under carpets
Each of these is a failure scenario waiting to happen.
⚡ Reason #8: People Overload Multi-Socket Extensions Constantly
A single extension strip with:
- phone chargers
- a heater
- a laptop
- a PC
- a TV
- a console
…is not “a little extra capacity.”
It’s a fire hazard.
The problem isn’t the strip — it’s the single cord feeding all of it.
That thin cord becomes a bottleneck for enormous current.
If you’ve ever touched a warm extension cord during operation —
that’s your warning sign.
⚡ Reason #9: Many People Use Extension Cords for High-Surge Loads
These loads are not cord-friendly:
- pressure washers
- air compressors
- vacuum cleaners
- welders
- space heaters
- kettles
- hair dryers
- angle grinders
- high-power tools
Surge currents of 30–60A can:
- melt plugs
- trip breakers
- damage motors
- burn cords
- cause insulation softening
Extension cords simply aren’t designed for surge-heavy loads.
⚡ Reason #10: The “Just One More Meter” Mentality
Every connection introduces risk.
One extension cord into another into another is:
- cumulative resistance
- cumulative voltage drop
- cumulative heat
- cumulative mechanical stress
This is known as “daisy chaining”.
It is one of the most common causes of garage, basement, and construction-site fires.
⚡ What You Should Do Instead
✔ Use proper wiring for permanent setups
Install new circuits or outlets.
✔ Use heavy-gauge cords
For tools: 12 AWG (or 2.5mm² EU).
For long runs: bigger.
✔ Always fully uncoil cord reels
Always.
✔ Avoid CCA cords
Buy 100% copper only.
✔ Don’t overload
One high-power device per cord.
✔ Replace worn cords immediately
Cracks = danger.
✔ Avoid daisy-chaining
Use a single, high-quality extension.
✔ Respect voltage drop
Long cords + big loads = no.
⚡ Amp Nerd Summary
Extension cords are dangerous because:
- people overload them
- they overheat when coiled
- voltage drop kills motors
- cheap cords use CCA
- ratings are misleading
- plugs loosen over time
- indoor cords get used outdoors
- multi-socket strips overwhelm single cords
- high-surge loads exceed capacity
- daisy-chaining compounds the risks
Extension cords are temporary tools, not permanent wiring solutions.
⚡ Final Thought
Extension cords don’t look dangerous — and that’s exactly why they’re risky.
Their convenience hides real physics: heat, resistance, and degradation.
Respect them, or they’ll burn you — literally.
Tomorrow:
Why LED Bulbs Fail So Quickly (Even Though They’re Supposed to Last 25,000 Hours).
