USE-2 is Underground Service Entrance cable, rated 600 V and 90°C in wet locations, and listed for direct burial without a raceway. That last point is what makes it different from THWN-2 and XHHW-2. Its limitation is the mirror image: USE-2 has no flame-retardant rating, so it may not be run inside a building unless it is also marked RHH or RHW-2.
| Property | Value |
|---|---|
| Voltage rating | 600 V |
| Temperature rating | 90°C wet and dry |
| Insulation | Cross-linked polyethylene (XLPE) |
| Conductor | Copper or aluminum, stranded |
| NEC article | Article 338 |
| Direct burial | Yes — listed for it without a raceway |
| Sunlight resistance | Yes, listed sunlight resistant |
| Flame rating | None unless dual-marked RHH / RHW-2 |
| Inside buildings | Not permitted past the service point unless dual-marked |
| Typical use | Underground service laterals, feeders to detached structures |
| Size | Ampacity |
|---|---|
| 14 AWG | 20 A |
| 12 AWG | 25 A |
| 10 AWG | 35 A |
| 8 AWG | 50 A |
| 6 AWG | 65 A |
| 4 AWG | 85 A |
| 3 AWG | 100 A |
| 2 AWG | 115 A |
| 1 AWG | 130 A |
| 1/0 AWG | 150 A |
| 2/0 AWG | 175 A |
| 3/0 AWG | 200 A |
| 4/0 AWG | 230 A |
This is the rule that catches people. Straight USE-2 with no additional marking is an outdoor and underground conductor. NEC 338.12(B)(1) prohibits underground service-entrance cable from being used for interior wiring, because the insulation has no flame-retardant additive and will propagate fire along a wall cavity.
Most USE-2 sold in the US is dual- or triple-marked USE-2 / RHH / RHW-2. The RHH and RHW-2 markings are flame-rated building wire types, and that marking is what makes it legal to continue the run inside the building. Read the print on the insulation before you buy — the two products look identical on the reel.
USE-2 is a single conductor for service and feeder work. You bury three or four of them in a trench. It is 90°C wet-rated, so it derates well, and it is what the utility side of a service lateral is usually made of.
UF-B is a multi-conductor cable assembly for branch circuits. It is limited to the 60°C column, so it needs a larger conductor for the same load, but it is a complete cable with a ground included and it is what you use for a circuit out to a shed or a post light.
THWN-2 or XHHW-2 in PVC conduit is the third option and often the best one for anything you might want to change later. It costs more up front, buries shallower under NEC Table 300.5 — 18 inches for PVC against 24 for direct burial — and lets you pull new conductors without digging.