How to Safely Install an Electrical Subpanel

Subpanels are the most effective way to manage electrical load in a garage or workshop without cluttering your home's main service panel. By creating a satellite hub, you shorten wire runs to heavy equipment and gain the flexibility to add individual circuits for lighting, tools, or EV chargers as your needs evolve. Done well, a subpanel installation is invisible and rock-solid. Done poorly, it is a fire hazard. The key is strict adherence to grounding and bonding protocols—specifically keeping your grounds and neutrals isolated within the subpanel—to ensure that if a fault occurs, the power trips back to your main panel instantly rather than electrifying the metal cabinet of your new subpanel.

  1. Square Up the Cabinet. Secure the subpanel enclosure to wall studs using appropriate wood screws. Ensure it is level and mounted at a comfortable working height, typically with the top breaker at or below six feet.
  2. Pull the Main Feed. Run a four-conductor feeder cable (two hots, one neutral, one ground) from the main service panel to the new subpanel location. Secure the cable with staples or clamps per local code requirements regarding spacing.
  3. Snap Home the Main. If your subpanel is a 'main lug only' type, you do not need a main breaker; otherwise, snap the main breaker into the subpanel's designated slots. Ensure it clicks firmly into the bus bar.
  4. Isolate Ground From Neutral. Install a separate grounding bar in the subpanel if one is not included. Connect your green or bare copper wire to this bar; strictly ensure the neutral bus is isolated from the cabinet by removing the bonding screw.
  5. Seat the Main Lugs. Attach the two hot conductors to the main lugs, the neutral to the neutral bus bar, and the ground to the grounding bar. Verify that all connections are tight and no stray wire strands are touching adjacent parts.
  6. Wire All Branch Circuits. Install your individual branch circuit breakers and connect the circuit wiring (hots to breakers, neutrals to neutral bar, grounds to ground bar). Test for continuity before closing the panel cover.