Extension Cord Selection Guide

The following charts list recommended extension cord specifications for proper use with 125 volt service.

50ft SJTW extension cord

Extension Cords Up To 100 Feet Long

Power Rating: Cord Length:
HP Watts Amps Under 50’ Long 50’ to 100’ Long
875 7 18 Gauge 18 Gauge
½ 1250 10 18 Gauge 16 Gauge
¾ 1625 13 16 Gauge 14 Gauge
1 1875 15 14 Gauge 12 Gauge
2500 20 12 Gauge 10 Gauge

Extension Cords – 150 Feet Long

Power Rating: Cord Length:
HP Watts Amps 150’ Long
875 7 14 Gauge
½ 1250 10 12 Gauge
1 1875 15 10 Gauge

Letter Designations

S Service Grade Extra hard service flexible cord for general use. 600 volt insulation.
SJ Junior Service Hard service flexible cord for general use. 300 volt insulation.
T Thermoplastic Wire is coated in PVC.
E Thermoplastic Wire is coated in an elastomer rubber.
P Parallel Conductor is insulated separately as in a typical lamp cord.
O Oil-Resistant Jacket is resistant to oil.
OO Oil-Resistant Jacket as well as the insulation inside the cord are oil resistant.
W Weather-Resistant Outdoor-rated. Resistance to wet conditions as well as UV protection.
“T” PVC Vinyl at -31F to +140F (-35C to +60C)
“E” TPE-rubber material at -58F too +221F (-50C to +105C)
V Vacuum Type Flexible jacket originally used for vacuum cleaner cords.

For Example: SJTW

SJTW is a common designation found on many extension cords.

SJTW Extension Cord Package Label

SJTW Extension Cord

The letters would stand for:

  • (SJ) Hard service flexible cord for general use. 300 volt insulation.
  • (T) Wire is coated in PVC.
  • (W) Resistance to wet conditions as well as UV protection.
    “T” Minimal temperature range of -31F to +140F (-35C to +60C)


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Related Item(s): Reference