What Is SER Cable?
SER stands for service entrance cable, style R, a multi-conductor cable with a reinforcement tape used for service entrances and as a feeder inside and outside the home. You will find SER running from the meter to the main panel, feeding subpanels in garages and additions, and connecting equipment such as a standby generator and its transfer switch back to the electrical panel. It is available with copper or aluminum conductors.
Where SER Cable Is Used
Service Entrance and Subpanel Feeders
SER is the common cable for bringing service conductors to the main panel and for feeding a subpanel that serves a garage, shop, addition, or finished basement. It bundles the hots, neutral, and ground in a single cable for a clean feeder run.
Standby Generator Connections
When a Generac or Kohler standby generator is installed, the wiring between the automatic transfer switch and the panel often uses SER cable sized for the service. If you are planning a whole-house standby system, the feeder cable is part of the install package. Browse our Generac home standby generators 10kW to 28kW collection when you are scoping the project.
Sizing SER for a Dwelling: The 83 Percent Rule
For a one-family dwelling, NEC 310.12 allows the service or feeder conductors that carry the entire dwelling load to be sized at not less than 83 percent of the service rating. For a 200-amp service that means a minimum conductor ampacity of 166 amps, which is why a 200-amp residential service commonly uses 4/0 aluminum or 2/0 copper. This dwelling allowance exists because the full load is rarely drawn for a sustained period.
Copper vs Aluminum SER
Aluminum SER is lighter and far more economical for large feeders, which is why 4/0 aluminum is the standard for a 200-amp residential service. Copper SER is heavier and costs more, but is chosen where smaller diameter or specific terminations are preferred. Both are code-compliant when sized and terminated correctly with the proper antioxidant on aluminum and torque-to-spec lugs.
Code and Safety Note
Service and feeder work involves the main panel and is among the most hazardous electrical tasks. The 83 percent allowance applies only to dwelling conductors carrying the entire load, and temperature correction or adjustment factors can change the required size. Follow the National Electrical Code and local amendments, confirm with your authority having jurisdiction, and use a licensed electrician for all service, feeder, transfer switch, and panel work.
IB Lighting carries SER cable in our electrical wire and cable collection, with free freight plus free freight insurance on every order. Call (800) 674-9019 to size a service feeder or a generator connection.