Heavy duty extension cord vs light duty extension cord: Heavy duty wins for anything that draws real power

The key difference is wire gauge and insulation. Light duty cords (16–18 gauge) are fine for phone chargers or a lamp, but heavy duty cords (10–14 gauge) handle power tools, space heaters, and window A/C units without overheating. Lower gauge = thicker wire = less resistance and heat. Heavy duty insulation stays flexible in cold weather; light duty gets brittle and risks fire. Never use a light duty cord for anything that draws power you can feel — it’ll melt or start a fire before the breaker trips.