What is the difference between SE cable and NM cable?

SE cable is rated for service entrance use with heavier insulation and sunlight resistance, while NM cable is designed only for interior branch circuit wiring and cannot be used for service runs.

Can service entrance cable be run inside a wall?

Yes, SE cable can be run inside a building when it feeds the main panel or a subpanel, but it must meet the installation requirements of the NEC for the specific application.

How long does service entrance cable typically last?

Service entrance cable can last 30 to 50 years or more when properly installed, though environmental exposure, rodent damage, or physical wear can shorten its useful life.

Does replacing service entrance cable require a permit?

Yes, replacing service entrance cable involves the utility service connection and requires a permit, inspection, and often coordination with the power company for a temporary disconnect.

What size service entrance cable is needed for a 200-amp service?

A 200-amp residential service typically uses 4/0 aluminum or 2/0 copper conductors, but the exact sizing depends on local code, conductor temperature ratings, and installation conditions.

Service Entrance Cable — SE Cable Types and Sizing

A service entrance cable is a multi-conductor cable rated for carrying utility power from the weatherhead or meter base to the main electrical panel, forming the critical link between the utility grid and the building's electrical system.

Service Entrance Cable diagram — labeled parts and installation context

What It Is

Service entrance cable, commonly designated SE cable per NEC Article 338, is manufactured with conductors and insulation rated for the higher demands of the service drop or service lateral connection. It runs from the point where utility power arrives at the building down to the main service equipment inside or outside the structure. The cable is rated for 600 volts and must withstand weather exposure on exterior runs while carrying the full load current of the electrical service without overheating.

The outer jacket is a flame-retardant thermoplastic designed to resist sunlight degradation on exposed exterior runs. Inside the jacket, the individual conductors are insulated with XHHW-2 rated material suitable for wet and dry locations. The cable is listed under UL 854 and must be installed in accordance with NEC Articles 230 and 338, which govern service entrance wiring methods and installation requirements.

Types

SEU cable contains two insulated hot conductors surrounded by a concentric wrap of bare neutral strands, all inside the outer jacket. This three-wire configuration is the standard for service entrance runs between the weatherhead and meter or between the meter and main panel, where the neutral is permitted to serve as both the grounded conductor and the equipment grounding path.

SER cable adds a separate bare equipment grounding conductor alongside the two hots and neutral, creating a four-wire cable required for subpanel feeders under current NEC rules. USE cable is rated for underground direct-burial service lateral installations and has a moisture-resistant jacket suitable for continuous ground contact. Conductor materials are typically aluminum for 100-amp and larger services, where 2-2-4 aluminum is standard for 100 amps and 4/0-4/0-2/0 aluminum is standard for 200 amps. Copper versions are available for shorter or specialty runs but cost significantly more.

Where It Is Used

Service entrance cable is found on virtually every residential building that receives overhead or underground utility service. On an overhead service, the cable runs from the weatherhead down the service mast or along the exterior wall to the meter socket, then continues from the meter into the main panel. On an underground service, USE cable runs from the utility transformer pad through a trench to the meter base.

In service upgrades, the existing SE cable is often replaced with a larger gauge to accommodate increased ampacity. A home upgrading from 100-amp to 200-amp service requires replacing the SE cable along with the meter socket, main panel, and grounding system. SE cable is also used for interior feeder runs between the main panel and subpanels located in garages, basements, or additions.

How to Identify One

Look for a heavy-gauge cable with a gray or black thermoplastic outer jacket running from the weatherhead or meter base into the main panel. The jacket is printed with the cable type designation (SE, SEU, SER, or USE), conductor sizes, voltage rating (600V), and the UL listing mark. The cable has a flat or oval cross-section profile because the conductors are arranged side by side rather than in a round configuration.

At the weatherhead, the cable enters through the bottom of the fitting with the individual conductors extending out the top to connect to the utility service drop. At the meter socket and panel, the cable terminates at large lug connections sized to match the conductor gauge.

Replacement

Replacement is needed when the jacket is cracked or sun-damaged, conductors are corroded at termination points, insulation shows heat discoloration or melting, or the cable is undersized for a service upgrade. A permit and utility coordination are required for service entrance cable replacement because the utility must pull the meter to de-energize the service conductors.

During replacement, the electrician installs the new cable, makes connections at the weatherhead, meter socket, and main panel, and the utility reconnects the meter after inspection. The entire process typically requires coordination between the homeowner, the electrical contractor, the building department, and the utility company.