4 Things to Know About Extension Cord Warmth and Duty Cycle

Duty cycle matters more than wattage A 1500W space heater running for hours will heat up a cord far more than a 1500W kettle running for four minutes. Sustained current causes resistance heating in the cord itself.

A 14-gauge cord is technically fine for both devices Both pull about 12.5 amps on a 120V circuit, and 14-gauge is rated for 15 amps. But it will get warm under a continuous load like a space heater.

Slight warmth is normal, but hot is not If the cord feels hot enough to be uncomfortable to touch, or if you’re running it through a tight coil, size up to a 12-gauge cord. A little warmth is just physics.

Space heaters are more sensitive to voltage drop than kettles Many space heaters run at the edge of the circuit, so they react poorly to any voltage drop in an extension cord. Kettles are on and off before heat builds up.