No cord is best; plug a space heater into a wall outlet. If you must, use a short 12–14 AWG, 15A+ cord with one outlet, laid flat and uncoiled.
Space heaters warm small areas fast, yet they draw a lot of current. A typical unit runs up to 1,500 watts on 120 volts, roughly 12.5 amps. That load can heat flimsy cords and bargain strips. Fire agencies and safety groups advise a direct wall connection with no sharing. When that’s not possible, the right heavy-duty cord and careful setup can keep risk low.
Quick Answer First: Cord Size, Length, And Rating
Pick a short, heavy-duty extension with thick copper, one outlet, and a printed 15A or higher rating. The lower the AWG number, the thicker the wire. Keep the run short to limit voltage drop, and never coil the cable during use.
| Gauge (AWG) | Rated Amps* | Max Cord Length To Stay Within Range |
|---|---|---|
| 16 | Up to ~10 A | Not suitable for space heaters |
| 14 | 14–15 A | Up to ~50 ft for a 12.5 A load |
| 12 | 16–20 A | Up to ~100 ft for a 12.5 A load |
| 10 | 21–30 A | Long runs only when unavoidable |
*Amp ranges reflect common consumer guidance for general-purpose cords. Always verify the rating printed on the cord jacket.
Using An Extension Cord For A Space Heater: When It’s A Last Resort
Direct-to-outlet keeps resistance and heat at the connection low. Still, rooms aren’t perfect. If furniture blocks the only receptacle, a short, thick, single-outlet cord can bridge the gap while you adjust the layout or plan a better outlet location.
What “Heavy-Duty” Actually Means
For heater loads, start at 14 AWG and go thicker to 12 AWG as length grows or if a plug or plate feels warm. Look for a clear 15A or 20A rating and a UL or ETL mark. Avoid 16 AWG for heaters.
Length And Voltage Drop
Every foot adds resistance. Shorter runs keep the heater happy and the plug cool. If the plug or outlet warms, stop and shorten the run or move the unit.
Where A GFCI Makes Sense
Near water or damp floors—garages, basements, laundry areas—a GFCI outlet adds shock protection. Use only on a dry, stable surface and schedule an upgrade if those outlets are missing.
Best Extension Cord For A Space Heater: Specs That Actually Matter
Scan the jacket and plug for these specs before you buy.
Gauge And Amp Rating
Up to about 25–50 feet, 14 AWG with a 15A rating is the floor. For 50–100 feet, 12 AWG is the practical pick for a 1,500 W heater.
Single-Outlet, No Extras
Choose one receptacle. Multi-taps invite extra loads that raise heat. A single outlet enforces a one-appliance rule.
Plug And Receptacle Quality
Full-size straight-blade plugs grip better than tiny low-profile styles. A lighted end helps confirm power. If the fit is loose, swap cords or use a different receptacle.
Jacket, Temperature, And Use Rating
Indoor cords marked SJT or SJTW suit most rooms. For patios or unheated shops, an outdoor-rated SJTW jacket stays flexible in the cold.
Certification Marks
Look for UL or ETL listing on both the cord and the heater. The mark should match the printed rating.
How Heater Power Draw Shapes Your Cord Choice
A 1,500 W heater on high pulls close to the limit of many 15-amp circuits. The cord and every contact point must pass that current without warming up. Thick copper lowers resistance, which keeps plugs cool and gives the heating element a steady supply. Thin wire or long runs waste energy as heat along the cord and may drop the voltage enough to hurt performance.
That’s why 16 AWG cords are out for heaters, even if a package claims a 13A rating. Real rooms add small losses at worn outlets, loose back-stabbed connections, and tired breakers. Starting with 14 AWG for short runs and 12 AWG for longer runs gives you headroom for those everyday imperfections.
What To Avoid With Space Heaters And Cords
Even with the right gauge, some habits add risk. Skip these.
Power Strips And Surge Protectors
These are small cords with extra outlets and thin bus bars. Heaters can overheat them fast. Use the wall outlet.
Daisy-Chaining
Plugging one cord into another stacks resistance and weakens connections. If one cord can’t reach, move the heater or pick a closer receptacle.
Running Under Rugs Or Coils
Textiles and tight coils trap heat. Leave the cord flat, visible, and uncoiled. Use a low-rise cover only when crossing a walkway.
Adapters And Multi-Way Taps
Three-to-two adapters, Y-adapters, and outlet multipliers add extra contact points. A single, proper connector is best.
Sample Setups That Work
Short Indoor Run To A Nearby Outlet
Heater on a level floor with a 3-foot clear zone. One 14 AWG, 15A, single-outlet cord, 10–25 feet, fully uncoiled. Nothing else on that cord or outlet. Check the plug after 10 minutes; cool to the touch is the goal.
Longer Run Across A Large Room
Furniture blocks the closest receptacle, so you use a 12 AWG, 15/20A-rated, single-outlet cord at 50–75 feet. Route along the baseboard with a cord cover at the doorway. After a few minutes on high, the plug and plate should stay cool.
Quick Safety Tune-Up For Any Space Heater
Before you think about cords, check the heater and plan placement.
- Keep a 3-foot clear zone around the unit.
- Use a stable, flat surface where no one will bump it.
- Pick a model with tip-over and over-temperature shutoff, and test those features at the start of the season.
- Plug straight into a receptacle when you can. The CPSC and the U.S. Fire Administration say it plainly.
- If a cord is unavoidable, match gauge to distance. The ESFI chart is a handy cross-check.
- Turn the unit off when you leave the room or go to sleep.
- Inspect the plug and cord often; damage or a loose fit means stop and replace.
Cord Routing That Stays Out Of Trouble
Route along baseboards, not across open floors. Where a crossing can’t be avoided, use a low-profile cover made for power cables and tape the edges to stop snags. Keep cords away from floor registers and portable fans that could move hot air over the jacket. Teach kids and pets to steer clear of the cable and the hot front of the heater.
| Feature | Good | Skip |
|---|---|---|
| Wire Gauge | 14 AWG short runs; 12 AWG longer | 16 AWG or thinner |
| Outlet Count | Single receptacle | Multi-tap heads |
| Length | Shortest that reaches flat on the floor | Slack loops or coils |
| Certification | UL or ETL mark | No listing |
| Jacket Marking | SJT/SJTW with clear amp rating | Missing or faded print |
| Connector Fit | Snug blades | Loose or scorched |
Why Many Pros Say “No Cord”
Space heaters often run near the limit of a 15-amp circuit on high. That leaves little headroom for long runs, worn outlets, or thin copper. Each weak point becomes a mini heater, sometimes hidden behind furniture. Keeping the path short and solid cuts risk fast.
Outlet Quality And Aging Homes
Old receptacles can grip poorly or hide loose wiring behind the yoke. Both create hot spots when a heater runs at full power. If a cord wiggles out easily or you see browning on the faceplate, stop using that location. Replace worn outlets and upgrade a frequently used heater location to a modern, tamper-resistant receptacle with a solid back-wire clamp.
Edge Cases: Garages, Shops, And Patios
Unfinished spaces bring dust, drafts, and sometimes damp floors. Use outdoor-rated SJTW cords only when needed, keep plugs off the floor, and avoid running cables where cars roll or tools drag. In damp zones, a GFCI outlet adds a layer of protection against shock. For patios, pick a heater listed for outdoor use and keep cords away from traffic paths.
Picking The Right Size: A Step-By-Step
1) Read The Heater Rating Plate
Find the wattage on the back or base. Many portables list 1,500 W on high and a lower setting around 750–1,000 W. Use the maximum for sizing.
2) Check Your Outlet And Circuit
Use a tight receptacle. If the plate warms after a few minutes on high, stop and move. Avoid sharing the circuit with toasters, vacuums, or hair dryers.
3) Match Gauge To Distance
Ten to twenty-five feet: 14 AWG. Fifty to one hundred feet: 12 AWG. Anything past that inside a home suggests you need another outlet.
4) Keep It Flat And Visible
Route along a baseboard, not under rugs or through a doorway. Use a low-rise cover only when crossing a walkway.
5) Test For Heat Rise
After five to ten minutes on high, touch the jacket, plug, and outlet plate. All should feel cool. Any warmth calls for a shorter run, thicker gauge, or a direct wall connection.
Key Takeaways For Picking A Cord
- Wall outlet beats any cord.
- When you must extend, use 14 AWG for short runs and 12 AWG for longer ones.
- Choose a single-outlet, UL/ETL-listed cord, uncoiled and flat.
- Check for heat at the plug and outlet after a few minutes on high.
- If a setup needs more than 100 feet, add a receptacle instead.
Choose cords that run cool. Keep checks simple and regular on cold days now.