How to Install an Electrical Subpanel

We make it easy for you to add circuits with our step-by-step guide to installing an electrical subpanel.

electrical subpanel

BHG / Kevin Norris

Project Overview
  • Total Time: 2 hours
  • Skill Level: Intermediate

If your home's service panel doesn't have room for new circuit breakers and you cannot use tandem breakers, a subpanel might be the answer. A subpanel connects to the main service panel with a thick three-wire cable. The feeder breaker in the main panel acts as the main disconnect for the subpanel. Before installing a subpanel, consult with an inspector to make sure you do not overload your overall system.

A subpanel has separate bus bars for neutral and ground wires and typically has no main breaker. It may not be labeled "subpanel." Instead, it might be labeled "lugs only." Additionally, it might be a different brand than the main panel. Have the inspector approve the subpanel, the feeder cable, and the feeder breaker before you start installing a subpanel.

Safety is most important when installing anything with wires or electrical work. When dealing with electrical projects, shut off the power first. Before you begin installing a subpanel, shut off the main breaker in the service panel.

What You'll Need

Equipment / Tools

  • Screwdriver
  • Hammer
  • Voltage tester
  • Flashlight
  • Strippers
  • Lineman's pliers
  • Long-nose pliers


  • Subpanel
  • Mounting screws
  • Approved feeder cable
  • Staples or cable clamps
  • Approved feeder breaker
  • Breakers for the new circuits


  1. mount subpanel

    BHG / Kevin Norris

    Mount Subpanel

    Mount the subpanel about a foot away from the main service panel. Determine how far the wires will have to travel in the subpanel and pull wires (shown) or add cable and strip sheathing accordingly. Remove a knockout slug, slide the wires through, and clamp the cable.

    Related: Basic Wiring Techniques You Need to Know

  2. plan route for electrical subpanel

    BHG / Kevin Norris

    Plan Route

    At the main service panel, plan the routes for the four wires: ground, neutral, and two hot wires (black and red). Strip the sheathing, remove a knockout slug, and clamp the cable. Route the neutral and ground wires carefully and connect them to their bus bar(s).

    Editor's tip: Professional electricians take pride in the way they run wires into a service panel or subpanel. In a well-wired panel, wires route in neat paths around the perimeter, making it easy to tell which wire goes to which breaker. More important, orderly wires are less likely to brush against hot bus bars, which would create a serious fire hazard.

  3. stripping wires for installing electric subpanel

    BHG / Kevin Norris

    Strip Wires

    Route, cut, and strip the red and black wires. Connect them to the feeder breaker. Snap the breaker into place.

  4. connecting wires to electrical subpanel

    BHG / Kevin Norris

    Connect Wires

    In the subpanel, route the feeder wires, cut and strip them, and connect to terminals. Connect the black and red wires to the hot bus bars, the neutral wire to the main neutral terminal, and the ground wire to the ground bus bar.

  5. finish connecting wires

    BHG / Kevin Norris

    Finish Connecting Wires

    Run cable for new circuits into the subpanel and clamp the cable. For each circuit, route wires around the perimeter, connect the ground wire to the ground bus bar, the white wire to the neutral bus bar, and the hot wire to a circuit breaker.

    Related: How Ground Wires Can Help Protect Your Home's Electrical System

Frequently Asked Questions

  • How high off the ground should a subpanel be mounted?

    The top of the subpanel must be at least 78 inches above the floor.

  • Does a subpanel need a separate ground rod or bar?

    If the subpanel is on a separate building, it needs a ground bar. However, it doesn't need one if it's located on the same building as the main panel since all the ground wires bond back at the main panel together with the neutrals.

  • If I can't mount the subpanel within a foot of the main panel, how far away can the subpanel be mounted?

    You can place a subpanel anywhere in your house regardless of where the main panel is. 

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