Do I need a sub-panel for a detached garage in New Brunswick?

Yes, in almost every practical situation a detached garage in New Brunswick needs its own sub-panel rather than running individual circuits from the house panel. While the NB Electrical Code does not technically prohibit running a single circuit to a small detached structure, any garage that will have more than one or two circuits — meaning any garage with lights, outlets, a door opener, and any additional loads — should have a properly installed sub-panel.

The reason is both practical and code-driven. Running multiple individual circuits from your house panel to a detached garage means pulling multiple sets of wire through a long underground conduit run — which is more expensive in wire cost, more difficult to install, and harder to troubleshoot or expand later. A sub-panel, by contrast, requires only one feeder cable from the house to the garage, where it connects to a local panel that distributes power to all the garage circuits. This is cleaner, more efficient, and allows you to add circuits in the future by simply adding breakers to the garage sub-panel rather than pulling new wire all the way back to the house.

From a code perspective, the sub-panel in a detached garage must have its own main disconnect — either a main breaker panel or a separate disconnect switch ahead of the panel. This is a critical requirement that differs from a sub-panel inside the same building as the main panel. The disconnect allows you (or a firefighter) to shut off all power to the detached garage from a single point at the garage itself. Additionally, the grounding and bonding in a detached structure sub-panel is different from an interior sub-panel: the neutral bar and ground bar must be separated (not bonded together as they are at the main panel), and the sub-panel must have its own grounding electrode — typically two ground rods driven at least 3 metres apart near the garage.

Sizing the sub-panel correctly for NB conditions is important. A minimum 60-amp sub-panel is sufficient for a basic garage with lighting, a few outlets, and a garage door opener. However, given New Brunswick's climate — where you will almost certainly want electric heat or at least the option of plugging in a portable heater, and where EV charger installations are becoming increasingly common — a 100-amp sub-panel is the better investment. The cost difference between a 60-amp and 100-amp panel is modest (roughly $500 to $1,000 more for the larger panel and heavier feeder cable), but upgrading later means re-trenching, re-pulling wire, and possibly upgrading the house panel as well.

The feeder cable from the house to the garage must be run underground in conduit, buried below the frost line — that means a minimum of 4 feet deep in southern NB and up to 5 feet in northern communities. This frost depth requirement makes the trench the most labour-intensive part of the project. In total, installing a 100-amp sub-panel in a detached garage located 30 to 60 feet from the house runs $2,500 to $5,000 in the New Brunswick market, including trenching, conduit, feeder cable, the panel, and an electrician's labour. This is not a DIY project — all garage electrical work in NB requires a permit and must be performed by a licensed electrician. The inspection process verifies proper grounding, correct wire sizing for the cable run distance (to avoid voltage drop), GFCI protection on all garage receptacles, and compliant bonding at the sub-panel.

One common mistake NB homeowners make is having the garage sub-panel installed with just enough capacity for today's needs. Think about what you might want in five or ten years — an EV charger, a workshop air compressor, an electric unit heater, or even a hot tub on the garage pad — and size accordingly. The trenching and conduit work is the expensive part, and you only want to do it once. Need help finding a licensed electrician for your detached garage? Browse contractors through the New Brunswick Construction Network at newbrunswickconstructionnetwork.com.