Symptoms
- Cord is hot along its length or at the plug while running a heater
- Heater trips a breaker or shuts off unexpectedly
- Cord shows melting, discoloration, or a burning smell
- Cord is a thin, light-duty type not rated for heaters
Likely causes
- CommonCord gauge too thin for the heater's amperage drawSpace heaters often draw close to 12–15 amps, which most light-duty extension cords can't handle safely.
- CommonManufacturer explicitly warns against extension cords for that heaterMany space heater manuals say to plug directly into a wall outlet only.
- PossibleCord is coiled while in use, trapping heatCoiling reduces a cord's safe heat dissipation even if the gauge is adequate.
- PossibleCircuit itself is overloaded with other devicesMultiple high-draw devices on the same circuit compound the risk.
What to do
- Stop using the extension cord for the heater immediately if it's hot, melted, or discolored.
- Check the heater's manual; most explicitly recommend plugging directly into a wall outlet, not an extension cord.
- If a cord must be used, choose a heavy-duty 12-gauge cord rated for at least 15 amps, fully uncoiled.
- Don't run other high-draw appliances on the same outlet or circuit as the heater.
- Never leave a space heater running unattended or overnight, regardless of the power setup.
- If the outlet or breaker feels warm or trips repeatedly, stop and have an electrician check that circuit.
Tools and parts
- None required
Heavy-duty 12-gauge extension cordSearch: “12 gauge indoor extension cord for space heater”
When to call a pro
If the outlet or breaker shows signs of overheating or trips repeatedly, have an electrician inspect that circuit before using a space heater on it again.
Safety
Use caution
Space heaters plugged into an undersized or coiled extension cord are a common cause of house fires; plug directly into the wall whenever possible.