Is It Safe to Use an Extension Cord Permanently for a Space Heater in an Older Home?

Short answer

Why people ask this

People wonder if they can run a space heater via an extension cord for months because their older home has limited outlets or rooms that stay cold. They also worry that old two‑prong or worn outlets may not handle a heater’s plug directly. Older homes may have 15‑amp circuits, knob‑and‑tube or aluminum wiring, and no AFCI/GFCI protection. A 1500W heater draws about 12.5 amps, which pushes many older circuits near their limits. Long-term use through an extension cord increases heat and resistance at every connection point.

When it might be safe

There are no commonly accepted situations where this is considered safe.

When it is not safe

• Running a 1500W heater (≈12.5A at 120V) through a light‑duty or coiled cord creates overheating at the plug and cord jacket
• Using cords under rugs or behind heavy furniture in drafty older rooms traps heat and hides damage
• Connecting to worn, two‑prong, or ungrounded outlets common in older homes increases arcing risk
• Daisy‑chaining power strips or using cord reels with a space heater raises resistance and failure points
• Permanent use on 15A circuits already serving lights and receptacles can trip breakers or overheat conductors

Possible risks

• Fire from overheated cord, plug blades, or aged receptacles in older wiring systems
• Melted insulation leading to shorts, arcing, and ignition behind plaster or baseboards
• Breaker trips or, worse, no trip due to degraded breakers common in older panels
• Shock risk with ungrounded two‑prong outlets or missing GFCI/AFCI protection
• Damage to the heater’s plug and receptacle from sustained high‑temperature cycling

Safer alternatives

• Plug the heater directly into a dedicated 15/20A receptacle; avoid power strips and extension cords
• Have an electrician add a new grounded circuit/receptacle near the room, ideally 20A with AFCI where required and GFCI if in damp areas
• Use a lower‑wattage heater (e.g., 750–1000W) and verify the circuit load; never exceed about 80% of breaker rating
• Improve room heat without extra electrical load: weather‑strip, seal drafts, add door sweeps and insulation
• Consider permanently installed solutions (baseboard, wall panel, or mini‑split) on properly sized circuits

Bottom line

Don’t use an extension cord permanently for a space heater in an older home. High, continuous current plus aging outlets and wiring is a common recipe for overheating—use a dedicated receptacle or upgrade the circuit instead.

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