SOOW vs SJOOW: choosing portable cord

Published Sep 30, 2026

SOOW and SJOOW are the rubber portable cords you see on job sites, stage rigs, pumps and shop equipment. The letters tell you almost everything: voltage class, jacket and insulation compound, oil resistance and outdoor rating. The main choice between the two comes down to voltage and how rough the job is.

Decoding the letters

Portable cord types are listed in NEC Table 400.4. The common letters:

S: service grade, rated 600 V, with a heavier jacket.
SJ: junior service, rated 300 V, with a thinner jacket.
E: thermoplastic elastomer (TPE) compound. No E means thermoset rubber.
O: oil-resistant outer jacket.
OO: oil-resistant jacket and oil-resistant conductor insulation.
W: rated for wet locations and outdoor use, with sunlight resistance.
T: thermoplastic (PVC), as in SJT and STO.

So SOOW is a 600 V service cord with oil-resistant rubber jacket and insulation, rated for outdoor use. SJOOW is the same build at 300 V with a thinner jacket.

Side by side

	SOOW	SJOOW
Voltage rating	600 V	300 V
Jacket	Heavier thermoset rubber	Thinner thermoset rubber
Oil resistance	Jacket and insulation	Jacket and insulation
Outdoor and wet use	Yes (W)	Yes (W)
Common sizes	18 AWG to 2 AWG	18 AWG to 10 AWG
Weight and flexibility	Heavier, stiffer	Lighter, easier to coil
Price	Higher	Lower

Which one to buy

Choose SJOOW for 120 V work: extension cords, pigtails for small tools and lights, and equipment cords where the cord is not dragged across concrete all day. It is lighter and easier to coil, and it costs less per foot.

Choose SOOW when any of these apply:

The circuit is over 300 V, such as 480 V or 600 V equipment.
The cord will be dragged, driven over or pulled across rebar and gravel.
You need a size larger than 10 AWG.
The spec or the equipment maker calls for 600 V cord.

240 V single phase is under the 300 V SJ limit, so SJOOW is technically fine for many 240 V tools; SOOW is still the common choice on job sites for its tougher jacket.

Ampacity comes from a different table

Portable cord ampacity is not taken from Table 310.16. It comes from NEC Table 400.5(A)(1), which gives values for cords with three current-carrying conductors and for cords with two. A 12/3 cord where the green conductor is only an equipment ground counts as two current-carrying conductors. Use the right column, apply the temperature correction if the cord runs hot, and protect it at a rating the table allows.

Where cord is not allowed

NEC 400.12 lists uses that are prohibited even with the toughest cord, including:

As a substitute for the fixed wiring of a building.
Run through holes in walls, ceilings or floors, or through doorways and windows.
Attached to building surfaces or concealed behind walls or ceilings.

If the run is permanent, it needs a permanent wiring method.

Other cords in the same family

SEOOW / SJEOOW: the TPE versions. Lighter than rubber cord of the same size, and flexible in the cold.
Yellow SOOW and SJOOW: the same cords in high-visibility yellow for job sites.
SJTOW: PVC jacket. Cheaper, less flexible in the cold, fine for light duty.

Shop portable cord

Verify with your local code. Cord ratings, permitted uses and ampacity depend on the NEC edition in force and on the equipment listing. Check the cord legend and the equipment instructions before use.