Quick answer. SOOW is a North American portable cord: S = service grade (600 V), OO = oil-resistant insulation and oil-resistant jacket, W = weather- and water-resistant. It is listed under UL 62, sold from 18 AWG to 2 AWG with 2–5 conductors, and is the standard cord for generators, shop tools, stage power and portable equipment. SJOOW is the same construction at "junior" service voltage — 300 V instead of 600 V. Type W is often searched alongside these cords, but it belongs to a different product family — a portable power cable, not a UL 62 cord.
Last reviewed: November 2026.
The letters, decoded
Each letter in the designation is a specific claim about the cable, not marketing:
| Letter | Meaning | Practical consequence |
|---|---|---|
| S | Service grade | 600 V rated cord (vs J = junior, 300 V) |
| SJ | Junior service | 300 V rated cord |
| O (first) | Oil-resistant insulation | Conductor insulation survives oil contact |
| O (second) | Oil-resistant jacket | Outer jacket resists oil, coolants and solvents |
| W | Weather-resistant | Suitable for wet locations and outdoor exposure |
| E (as in SJEOOW) | Elastomeric compound (rubber-based) | More flexible across temperature than thermoplastic |
So SOOW reads as: 600 V service cord, oil-resistant insulation, oil-resistant weatherproof jacket. SJOOW reads the same except at 300 V. When an E appears (SJEOOW, SEOOW), the jacket/insulation is an elastomer rather than a PVC thermoplastic — softer in cold weather and generally the better choice for cord that gets coiled daily.
SOOW vs SJOOW: the only real difference is voltage
Construction is otherwise identical — copper conductors, oil-resistant insulation, oil-resistant weatherproof jacket. What changes:
- SOOW: 600 V, commonly 18 AWG–2 AWG, 2–5 conductors
- SJOOW: 300 V, typically 18 AWG–10 AWG light-duty sizes
Both are flexible cords — designed to move, coil and flex for the life of the equipment, not to be pulled into conduit as fixed building wiring. Using a 300 V SJOOW anywhere the circuit can exceed 300 V is a direct safety violation, and the jacket marking is the first thing an inspector reads.
One family boundary worth knowing
Type W gets searched alongside SOOW, and quoting the two in the same breath is how specs go wrong. Type W is not a UL 62 flexible cord — it is a portable power cable, roughly 8 AWG to 2000 kcmil at 600 V or 2000 V, built for temporary distribution, mining and heavy equipment, where the jacket has to survive dragging and crushing rather than daily coiling. Different family, different standard, different duty.
The practical consequence: in the 8–2 AWG overlap, "large SOOW" is not a cheaper Type W. Cord stranding and jacket are optimised for flexibility, so dragging a cord where a power cable belongs damages the jacket long before any electrical limit is reached. Size the product to the duty, not to the nearest familiar letter string.
Sizes and ampacity
Cord ampacity is not the same as building-wire ampacity — flexible cords carry their own tables. Typical published values for 3-conductor SOOW at 30 °C ambient:
| AWG | ≈ mm² | Typical ampacity |
|---|---|---|
| 18 | 0.82 | 7 A |
| 16 | 1.31 | 10 A |
| 14 | 2.08 | 15 A |
| 12 | 3.31 | 20 A |
| 10 | 5.26 | 30 A |
Treat these as orientation values, not purchase criteria — ampacity moves with conductor count, insulation compound and ambient temperature, so the manufacturer's datasheet for the exact construction governs. For the AWG-to-mm² arithmetic on any other size, the AWG to mm² conversion chart covers the full table.
Where each belongs in practice
| Application | Right choice | Why |
|---|---|---|
| Generator lead, shop tool, stage power | SOOW (or SJEOOW for daily coiling in cold) | 600 V, flexible, oil and weather resistant |
| Light appliance, office equipment | SJOOW | 300 V is sufficient; cheaper |
| Welding machine primary lead | SOOW sized to nameplate | Secondary leads are welding cable, a different product |
| Construction site temporary distribution | Portable power cable (Type W family) — not a cord | Cord jackets fail on dragging and crushing |
| Mining, dragline, heavy equipment | Type W / mining variants | Engineered for the duty cycle |
| Exposed PV source circuits | None of these — use listed PV wire | See below |
The last row is the mistake worth its own paragraph. SOOW is weather-resistant, but it is not sunlight-resistant in the UL 4703 sense and not listed for exposed PV source circuits; NEC practice points to PV wire or USE-2 there. If a solar quote offers SOOW as a cheaper "equivalent", decline it — the listing gap is exactly the kind of thing that fails inspection years later. What PV wire requires and how Type X/Type R differ is covered in the UL 4703 PV wire guide, and the PV wire vs USE-2 explainer covers the listing details.
Importing perspective: UL terms vs international equivalents
Buyers outside North America search these terms because US-origin equipment specifies them — but the equivalents are not drop-in substitutions:
- Europe / IEC: the closest rough-duty flexible cord is H07RN-F (rubber, 450/750 V, weather-resistant) or lighter H05RN-F for the 300 V class. Similar duty, different test regime.
- A cord marked SOOW is UL-listed to UL 62; H07RN-F is certified to IEC 60245 / EN 50525. A destination market that requires one will not automatically accept the other — match the certification to the market, then match the construction to the duty.
- Chinese and other export factories can produce to either, and often to both for the same size — so at RFQ stage, name the destination market and required listing first, the letter designation second. This is the same discipline as matching building wire to market: the BV/BVR vs IEC 60227 and UL 83 comparison shows how the logic works for fixed wiring.
Five buying mistakes worth avoiding
- Buying on voltage class without reading the circuit. 300 V SJOOW on a 600 V circuit is a spec failure, and the two jackets look almost identical.
- Assuming "W" means sunlight-resistant. Weather-resistant is not a PV listing; exposed solar source circuits need listed PV wire.
- Accepting copper-clad aluminum in a "copper" cord quote. Fine-stranded CCA exists and looks legitimate on a low quote; the conductor material test in the bare copper vs tinned vs CCA guide shows how to check.
- Specifying large SOOW for Type W duty. In the 8–2 AWG overlap the two are priced differently for a reason; temporary distribution that drags and crushes eats cord jackets.
- Ordering the certification, not the letters. SOOW guarantees UL 62; it does not guarantee acceptance in a market that demands IEC certification, and vice versa. Name the market at RFQ.
FAQ
Q1: What does SOOW stand for? A: Service cord (600 V), with an oil-resistant conductor insulation, an oil-resistant jacket, and weather/water resistance — S-O-O-W. It is listed under UL 62 and is the standard flexible cord for portable equipment in North America.
Q2: What is the difference between SOOW and SJOOW? A: Voltage class. SOOW is 600 V service cord; SJOOW is "junior" service at 300 V. Construction is otherwise the same — oil-resistant insulation and jacket, weather-resistant. Pick by circuit voltage, and remember SJOOW is limited to light-duty sizes.
Q3: Is SOOW the same as Type W cable? A: No. SOOW is a UL 62 flexible cord (18–2 AWG, 600 V) for portable tools and equipment. Type W is a portable power cable to ICEA specifications (about 8 AWG to 2000 kcmil, 600 V or 2000 V) for temporary distribution and mining duty. They overlap in size range but are different products with different test regimes.
Q4: Can SOOW be used outdoors and in the rain? A: Yes for its intended duty — the W means weather-resistant, and SOOW is the default cord for outdoor generators and portable equipment. But weather resistance is not sunlight resistance, and it is not a substitute for listed PV wire on exposed solar source circuits.
Q5: Is there a European equivalent of SOOW? A: The closest in duty is H07RN-F (450/750 V rubber flexible cord to IEC 60245 / EN 50525), with H05RN-F at the light end. Similar construction, different certification — a market requiring UL 62 will not automatically accept H07RN-F, and the reverse. Match the listing to the destination market at RFQ stage.
Sourcing note
🔴 Disclaimer: letter designations, size ranges and ampacity tables vary between manufacturers and standards revisions. Confirm the current UL 62 / ICEA listing and the manufacturer's datasheet for the exact construction before purchase. This article is buying guidance, not a certification determination.
