It’s tempting to plug everything into one extension cord, especially when outlets are far away. But big appliances like aircons, refrigerators, flat irons and rice cookers draw a lot of current, and the wrong cord can overheat and start a fire. Here’s how to tell what’s safe, with an interactive load checker.
In this article
- The short answer
- Why extension cords overheat
- How to read an extension cord’s rating
- Extension cord load checker
- Appliance-by-appliance guide
- Why refrigerators are a special case
- Warning signs to stop using a cord
- How to choose a safer extension cord
- Quick math examples
- Safe habits with extension cords
- FAQ
The short answer
Aircons and other high-power heating appliances should be plugged directly into a properly rated wall outlet, ideally on their own circuit. A refrigerator should also go straight into the wall when possible. Light loads like phone chargers, lamps, laptops and routers are generally fine on a good-quality extension cord or power strip.
Why extension cords overheat
Every wire has resistance. When current flows, some energy turns into heat. Thin wires have higher resistance, so they heat up more. An extension cord is often thinner than your house wiring, and its plug, sockets and internal contacts add more resistance. When too much current flows, those weak points get hot, the plastic softens or melts, and in the worst case, a fire starts.
Loose or worn sockets make it worse. A plug that wiggles makes poor contact, and poor contact means more heat right at the socket.
How to read an extension cord’s rating
Look for the maximum current (amps) or power (watts) printed on the cord, plug or packaging, for example “10 A 250 V” or “2,200 W max”. To convert amps to watts at a typical 220–230 V supply:
Max watts ≈ amps × voltage
Example: 10 A × 220 V = 2,200 W
Then add up the watts of everything you plug in. Stay well below the maximum; using no more than about 80% of the rating gives a safety margin, especially for loads that run for hours.
Extension cord load checker
Will your extension cord handle it?
Appliance-by-appliance guide
| Appliance | Typical watts | On an extension cord? |
|---|---|---|
| Aircon | 650–2,000 W+ | No: use a dedicated wall outlet |
| Water heater | 3,000–5,000 W | No: needs its own circuit |
| Flat iron | 1,000–1,200 W | Avoid, especially with other loads |
| Rice cooker | 500–700 W | Only alone, on a heavy-duty cord |
| Refrigerator | 100–250 W running, higher at startup | Better on the wall outlet |
| Electric fan | 40–70 W | Usually fine |
| TV, laptop, router, chargers | 10–150 W | Fine on a good cord |
Why refrigerators are a special case
A ref doesn’t use much power while running, but its compressor draws a much higher current for a moment when it starts. A thin or long cord can cause a voltage drop that strains the compressor. Refs also run 24/7, so any weak connection has many hours to heat up. Plug it straight into the wall whenever you can.
Warning signs to stop using a cord
- The plug, socket or cable feels warm or hot.
- Brown or black marks around the sockets.
- A burning plastic smell.
- Crackling, buzzing or sparking when plugging in.
- Plugs that fall out or fit loosely.
- Cracked insulation or exposed copper.
If you notice any of these, unplug the cord (switch off the breaker first if it’s smoking) and replace it.
How to choose a safer extension cord
- Choose a rating higher than your total load, with margin.
- Prefer cords with a built-in breaker or overload protection.
- Pick a thicker cable for higher loads and keep it as short as practical.
- Look for proper safety certification marks from your country’s standards body.
- Avoid “daisy-chaining” (plugging one extension cord into another).
Learn more about cable thickness in our wire size guide, and what to do if a breaker keeps turning off in why your breaker keeps tripping.
Quick math examples
Example 1: A 10 A cord on 220 V can carry about 2,200 W. A TV (80 W), laptop (60 W), fan (55 W) and router (10 W) total about 205 W, only 9% of the rating. That’s safe.
Example 2: On the same cord, a flat iron (1,100 W) plus a rice cooker (650 W) total 1,750 W, about 80% of the rating, and both make heat for a long time. That’s too close for comfort. Plug them into separate wall outlets.
Example 3: A 1 HP aircon (800 W) plus a flat iron (1,100 W) plus a rice cooker (650 W) total 2,550 W, which is over the limit. The cord will overheat.
Safe habits with extension cords
- Uncoil the cord fully when using higher loads. A coiled cord traps heat.
- Don’t run cords under rugs, mattresses or furniture where heat can’t escape and damage can’t be seen.
- Don’t staple or nail cords to walls or floors.
- Unplug by holding the plug, not by pulling the cable.
- Keep cords away from water, sinks and wet floors.
- Treat extension cords as temporary. If you need one permanently, have an electrician add an outlet.
Following these habits prevents most extension-cord fires at home.