Don't use an extension cord with a space heater.

No. Even if the cord is rated for higher amperage, don’t do it.

The problem isn’t just the amperage rating. Space heaters are high-draw devices that run for hours, and extension cords—even heavy-duty ones—create resistance and heat at the connection points. Over time, that heat can melt the plug, the receptacle, or the cord itself, even if the wire gauge is technically sufficient. Fire departments see this exact scenario every winter.

The only safe way to run a space heater is plugged directly into a wall outlet. If you don’t have an outlet close enough, you need to rearrange the room or get a longer heater cord designed for that specific heater—not a generic extension cord. There is no extension cord that makes this okay.

Save the heavy-duty cord for power tools. A space heater gets the wall outlet or nothing.