Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.
Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.
Summary
An undersized extension cord can overheat and cause fire. Match the wire gauge to your generator's amperage and the distance the cord must travel. Always use an outdoor-rated cord with a three-prong grounded plug—never a male-to-male cord.
Necessary equipment
| Item | Note |
|---|---|
| Portable generator | |
| Extension cord material | Outdoor-rated, three-prong grounded, wire gauge matched to generator amperage and cord distance |
Specifications
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
Procedure
Estimated 10 min
AN UNDERSIZED CORD CAN OVERHEAT AND START A FIRE.
The cord insulation breaks down at high temperatures. Match the wire gauge to the generator amperage and the distance the cord travels.
DO NOT USE A MALE-TO-MALE EXTENSION CORD.
DO NOT CONNECT THE GENERATOR TO HOUSE WIRING. Exposed prongs can become energized. This can kill utility workers and neighbors on the same electrical transformer. Hire a licensed electrician for any house connection.
- FIND THE GENERATOR'S AMPERAGE RATING ON THE MANUFACTURER'S NAMEPLATE, OWNER'S MANUAL, OR LABEL ON THE GENERATOR FRAME.<1mReport a problem with step 1, Procedure
- MEASURE THE DISTANCE FROM THE GENERATOR TO THE FARTHEST APPLIANCE OR TOOL THE CORD MUST REACH. RECORD THIS DISTANCE IN FEET.1mReport a problem with step 2, Procedure
- CONSULT YOUR GENERATOR MANUFACTURER'S MANUAL TO FIND THE WIRE GAUGE TABLE FOR YOUR POWER REQUIREMENTS AND CORD DISTANCE.2mReport a problem with step 3, Procedure
- SELECT AN OUTDOOR-RATED EXTENSION CORD WITH A W DESIGNATION (SJTW OR STW). THE LABEL MUST SHOW A THREE-PRONG GROUNDED PLUG AND THE WIRE GAUGE FROM YOUR MANUAL.5mReport a problem with step 4, Procedure
- SELECT A CORD WITH PURE COPPER CONDUCTORS. AVOID ALUMINUM WIRE BECAUSE IT HAS HIGHER RESISTANCE AND PRODUCES MORE HEAT.1mReport a problem with step 5, Procedure
- EXAMINE THE CORD FOR DAMAGE BEFORE USE. LOOK FOR CUTS, CRACKS, OR EXPOSED WIRES. DO NOT USE A DAMAGED CORD.1mReport a problem with step 6, Procedure
Terminology
This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.
- wire gauge
- Also called: no common alternatives
- outdoor-rated extension cord
- Also called: no common alternatives
- amperage
- Also called: no common alternatives
- backfeeding
- Also called: no common alternatives
When to use a professional
STOP AND CALL A LICENSED ELECTRICIAN IF YOU NEED TO CONNECT THE GENERATOR TO YOUR HOUSE WIRING. This connection can kill workers and cause fires if done incorrectly. Only a qualified electrician can install the proper transfer switch or isolation device.
Common questions
What wire gauge do I need?
It depends on the generator amperage and cord length. Use the wire gauge table in this record or check your generator manual. A 15 amp generator needs at least 12 AWG for a 100 foot cord but only 14 AWG for up to 50 feet. A 30 amp generator needs 10 AWG.
Can I use a regular household extension cord?
No. Household extension cords are not rated for outdoor use and can overheat in bad weather. Always buy a cord marked for outdoor use with a W designation (SJTW or STW).
Why does cord length matter?
A longer cord has more electrical resistance, which causes voltage drop and heat. This is why a 100 foot cord needs thicker wire than a 50 foot cord that carries the same electrical load.
Is it safe to plug a generator into a house outlet?
No. This backfeeding creates danger. Electricity flows backward into house wiring and can kill utility workers. If you need house power during an outage, hire a licensed electrician to install a proper transfer switch.
What does the W rating on an extension cord mean?
The W means the cord is weather-resistant and can handle outdoor conditions including UV exposure, moisture, and temperature extremes. Always choose outdoor-rated cords for generator use.
Related procedures
- Match an extension cord to the appliance it will supply
- How far from the house should a generator be, and which way should the exhaust point?
- What size generator do I need, and how do I work out running watts and starting watts for the things I want to power?
- How to clean or change the air filter on a portable generator
Sources
Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.
Revision history
Current version 1 · updated 2026-08-03 · next review due 2027-08-03
- v1 · 2026-08-03First publication.
Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.
Comments and corrections
Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.
Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.