Cost to Install a Garage Subpanel

The cost to install a garage subpanel runs $700 to $1,800 for an attached garage fed with a short run from the main panel. A detached garage costs more, typically $1,800 to $3,500, because the wire has to run underground or overhead to a separate structure.

This guide covers what it costs to install a garage subpanel for workshop tools, an EV charger, a mini-split, or general lighting and outlets. It explains how to size the amperage correctly, and where trenching and permits add to the bill.

What It Costs to Install a Garage Subpanel

A subpanel is a smaller breaker box fed from your main panel. It lets you add several new circuits to one area without overloading the main panel's slots. For an attached garage, most homeowners pay $700 to $1,800 installed, including the subpanel itself, the feeder wire, and labor.

A detached garage costs more, because the feeder cable has to get from the house to the structure. It either gets buried in a trench or run overhead on a mast. That work alone can add $800 to $2,000 on top of the panel and wiring, depending on distance and whether the yard has to be dug up.

The table below shows typical installed pricing by scenario. The sections that follow explain what pushes a quote toward the low or high end.

Sizing the Subpanel: 60, 100, or 125 Amps

A 60-amp subpanel covers basic lighting, outlets, and a few power tools. It is the cheapest option. A 100-amp subpanel is the common choice today, because it leaves room for an EV charger, a mini-split, or a small compressor without maxing out.

A 125-amp subpanel is worth the extra cost if you plan to run heavier equipment, a welder, or multiple large loads at once. Undersizing now to save a few hundred dollars is one of the most common regrets homeowners report, usually once they add a second big tool or an EV charger later.

An electrician sizes the subpanel based on a load calculation, not guesswork. Tell them everything you plan to plug in eventually, including future EV charging, so they size it once instead of twice.

Attached vs. Detached Garage

An attached garage is the cheaper scenario, because the feeder wire usually runs a short distance through a shared wall or the attic space above. Labor is one to two hours to run the wire, plus time to mount and wire the subpanel itself.

A detached garage means the feeder has to cross open ground. Most electricians either trench a buried conduit, typically 18 to 24 inches deep per code, or run the cable overhead from a mast. Trenching is more common today, because it looks better and holds up longer. It also costs more upfront in labor and, if concrete or landscaping sits in the path, restoration.

If the garage already has any power at all, ask the electrician whether the existing wire can serve as the new feeder, or whether it needs to be upsized. Reusing an adequate existing run is one of the few ways to cut this job's cost meaningfully.

Does the Main Panel Have Room?

A subpanel needs a slot and available capacity at the main panel, same as any other circuit. If your main panel is already full or close to its rated capacity, the electrician has to address that first. That can mean a panel upgrade before the subpanel work even starts.

Our cost to replace an electrical panel guide covers what a service upgrade costs if your main panel needs more room before it can feed a garage subpanel.

This is worth confirming before you get quotes specifically for the subpanel. A bid that assumes your main panel has spare capacity can be off by a wide margin if it does not. Also, check the main panel brand first. If it is an old Federal Pacific unit, our cost to replace a Federal Pacific panel guide is worth reading, since that panel is not a safe foundation for a new subpanel.

What Drives the Price Up

Distance to a detached garage is the single biggest variable. Every additional 25 feet of trenching or overhead run adds labor, wire, and sometimes conduit cost. A garage set far back on the property costs meaningfully more than one just off the driveway.

Concrete, mature landscaping, or a paved path between the house and garage all add restoration cost after trenching. Rocky soil slows digging and adds hours. An overhead run avoids digging, but it needs a mast and proper clearance height, which brings its own material and permit rules.

If you are also wiring for an EV charger or a heat-and-cool mini-split in the garage, tell the electrician up front. Sizing the subpanel once for the full plan is cheaper than upsizing it later.

Permits and Inspection

A subpanel install is code-regulated work and needs a permit in every jurisdiction, typically $75 to $300 depending on the city and whether trenching is involved. The inspector checks the feeder wire size, the grounding and bonding, and the breaker sizing at both the main panel and the new subpanel.

If you are also rewiring parts of the garage itself for new outlets and lighting, our cost to rewire a house guide covers that broader scope and how it is typically priced alongside a subpanel.

Keep the permit and inspection paperwork afterward. An unpermitted subpanel is a common issue flagged during a home sale inspection.

DIY vs. Hiring an Electrician

This is a job for a licensed electrician. It involves working at the live main panel and sizing a feeder correctly for the distance and load. In many areas, an inspector will not sign off on owner-installed subpanel work at all.

The Electrical Safety Foundation International notes that improperly sized or grounded subpanels are a recurring cause of home electrical hazards. A licensed pro, however, knows exactly how to avoid that mistake.

How to Keep the Cost Down

First, size the subpanel for your full plan, including anything you expect to add within the next few years, so you avoid paying for a second upgrade later. Second, since a detached garage costs more, ask whether an existing conduit or utility trench can be reused for the new feeder.

Third, get three itemized quotes that separately list the subpanel, the feeder wire, any trenching or restoration, and the permit, so you can compare bids on equal terms. Finally, if a new 240V outlet for a specific tool is really all you need, and the garage sits close to the main panel, our cost to install a 240V outlet guide covers the cheaper single-circuit option instead.

Subpanels for Workshops vs. Living Space

A garage subpanel used mainly for tools and general power is a simpler job than one feeding a heated workshop, a mini-split, or a converted living space. Extra circuits for climate control or finished-space lighting add to the count, which adds labor even if the amperage stays the same.

If the garage is being converted into a living or working space with drywall and insulation, plan the subpanel and its circuit count around the finished layout, not the current bare shell. Adding a circuit later, after the walls are closed, costs far more than including it now.

Bottom Line

Budget $700 to $1,800 to install a garage subpanel on an attached garage, and $1,800 to $3,500 for a detached one that needs trenching. Size it for your long-term plan, not just today's needs.

Confirm the main panel has capacity, get the permit included, and hire a licensed electrician for the feeder run and the panel work.