Leaving Extension Cords Plugged In Turns Temporary Fixes Into Hazards, Engadget Reports

Extension cords are not permanent wiring additions and can become damaged over time if used continuously, ESFI says. Unplugging a cord when it is no longer needed also gives users a chance to inspect it for cracked insulation, loose connections or a plug that is getting hotter than preferred, the article notes.

The National Electrical Code draws a clear distinction in Section 400.12: flexible cords and cord sets should not replace a structure's fixed wiring. The code also prohibits running them through holes in walls, floors and ceilings, through doorways or windows, or anywhere they are likely to be physically damaged. The specific version and amendments of the NEC in effect may differ by location.

Time limits in extension cord guidance can be confusing. The NEC's temporary-installation rules include a 90-day limit for holiday decorative lighting and similar purposes, but that does not mean every extension cord in the United States becomes prohibited on day 91. A separate rule of thumb from the workplace safety organization MEMIC says that if equipment has been powered by an extension cord for more than 30 days, it is time to consider a permanent solution. For a home office, that could mean adding an outlet where it is needed rather than leaving an extension cord behind a desk for years. ESFI also recommends against covering cords because doing so can trap heat and lead to overheating.

The cord has its own limit. A circuit breaker does not protect every item plugged into an extension cord, and cords come in various wire gauges, lengths and current ratings. The cord must be able to support whatever is plugged into it. A laptop charger and a space heater place very different loads on a cord. Because extension cords can overheat and cause fires, the U.S. Fire Administration recommends that major appliances be plugged directly into wall outlets. Its guidance for portable heaters is simpler: never use an extension cord or power strip. Plugging a power strip into a smart plug can create a separate overload risk.

Daisy-chaining extension cords is not a safe workaround, according to ESFI, which also warns against placing cords under rugs or running them through doorways because those practices can lead to heat buildup or damage.

These failures are not purely theoretical. Loudoun County Fire and Rescue attributed a July 2026 house fire in Virginia to the electrical failure of an extension cord. Five occupants were displaced. The release did not specify what was plugged into the cord or how long it had been in use, so the incident does not indicate that leaving a cord unused and plugged in was the cause.

The practical guidance is straightforward: check the cord's rating, replace damaged cords and unplug temporary setups when finished. ESFI lists 25- to 50-foot 16-gauge cords for 1 to 13 amps, 14-gauge cords for 14 to 15 amps and 12- or 10-gauge cords for 16 to 20 amps.