Comparison: Best Space Heater Extension Cord (Updated | Dec 16th)

Standard indoor extension cords are not designed to handle the high electrical load a space heater requires, creating a serious fire hazard. They often have thinner wires that can overheat, melt, and start a fire. You must use a cord specifically rated for high-wattage appliances to ensure safety.

The most critical specification is the wire gauge, which measures the thickness of the wires inside the cord. For a space heater, you should look for a heavy-duty cord with a 14-gauge (AWG) wire or even a 12-gauge for longer runs and higher wattage heaters. A lower AWG number indicates a thicker, safer wire that can handle more current without overheating.

The letters ‘SJTW’ are a rating that describes the cord’s durability and suitability for different environments. ‘S’ indicates it’s a flexible service cord, ‘J’ means it has standard 300-volt insulation, ‘T’ signifies a thermoplastic (Vinyl) jacket, and ‘W’ means it is rated for outdoor and wet conditions. An SJTW cord is a durable, all-weather choice that provides an extra layer of safety.

While it’s always best to plug a heater directly into a wall outlet, if you must use a cord, keep it as short as possible. The longer the cord, the more electrical resistance there is, which can lead to voltage drop and overheating. For necessary use, opt for the shortest heavy-duty cord that meets your needs, typically under 25 feet.

You should avoid using flat, low-profile extension cords, often called ‘tape’ or ‘lamp’ cords, with space heaters. These cords almost always use thin, high-gauge wire (like 16 or 18 AWG) that is not rated for the high amperage of a heater. They are a major fire risk and should never be used for this purpose.

Look for a cord with a three-prong, grounded plug that matches your heater’s plug. A lighted indicator on the plug is a helpful feature that shows the cord has power. Additionally, a cord with a reinforced, strain-relief collar where the cord meets the plug and socket will prevent the internal wires from bending and breaking over time.

Check the power rating on your heater, usually listed in watts (W) or amps (A), and compare it to the cord’s rating. Most heavy-duty 14-gauge cords are rated for 1,875 watts (15 amps), which is sufficient for most standard 1,500-watt space heaters. Always ensure the cord’s rating is equal to or greater than the heater’s requirement.

Yes, investing in a high-quality, heavy-duty extension cord is absolutely worth the extra cost for the safety it provides. A cheap, undersized cord is a leading cause of electrical fires, while a proper cord is a one-time purchase that protects your home and your heater. Consider it a non-negotiable safety accessory rather than an optional accessory.