Service entrance cable comes in two main styles — SEU and SER — and while they share the "SE" family name, they're built differently and belong in different parts of the electrical system.
What They Have in Common
Both are UL 854 listed service entrance cables rated 600V with XHHW-2 (or similar) insulated conductors inside a gray sunlight-resistant PVC jacket. Both come in copper and aluminum — aluminum dominates residential work because of cost.
SEU: Style U (Unarmored, Flat)
SEU is the flat, oval cable you see running from the weatherhead down to the meter base and from the meter to the main panel. Construction:
- Two insulated phase conductors, side by side
- A bare concentric neutral wrapped around them
- Overall jacket
The concentric neutral works for service conductors because at the service, the neutral and equipment ground are bonded anyway. Typical use: meter to main panel, and overhead service drops.
SER: Style R (Round, with Ground)
SER is round and adds a conductor:
- Two or three insulated phase conductors
- An insulated neutral
- A separate bare ground
That fourth conductor is the whole point. Downstream of the main disconnect, the NEC requires neutral and ground to be separated — so a subpanel feeder needs an insulated neutral plus a ground. SER delivers exactly that. Typical uses: panel-to-subpanel feeders, feeding ranges and large appliances, and interior runs where the cable is treated like Type SE per NEC 338.
Quick Selection Table
| Application | Cable |
|---|---|
| Weatherhead to meter | SEU |
| Meter to main panel | SEU |
| Main panel to subpanel (attached garage, addition) | SER |
| Feeder to detached building (buried) | Neither — use conduit + THWN-2 or direct-burial feeder cable |
| Range/dryer circuit from panel | SER (where permitted) |
Common Sizes
Aluminum SER 2-2-2-4 (100 A feeder) and 4/0-4/0-2/0-4 (200 A service) are the volume movers. Copper versions run smaller gauge for the same ampacity. Remember NEC 310.12 allows service and feeder conductors serving a dwelling to be sized at 83% of the service rating — that's why 4/0 aluminum works for a 200 A residential service.
Buying Notes
- Aluminum SE cable uses AA-8000 series alloy — modern, code-compliant, and nothing like the 1960s aluminum wire that earned a bad reputation
- Use oxide inhibitor and torque terminations to spec on aluminum
- SE cable is sunlight resistant but not rated for direct burial
We stock copper service entrance cable and aluminum service entrance cable cut to length. Comparing conductor materials? Read our copper vs aluminum guide.
