How many electrical circuits does a typical garage need and what should each one be for?

The number of circuits your garage needs depends entirely on how you use the space, but even a basic garage benefits from more circuits than most people expect. Planning adequate circuits during initial wiring saves you from running extension cords and tripping breakers later.

A basic attached garage used only for parking and light storage needs a minimum of two circuits. One 15-amp circuit handles the lighting and garage door opener. A second 20-amp circuit serves the general-purpose receptacles along the walls. This meets the Ontario Electrical Safety Code minimum requirements and costs the least to install, but it limits what you can do in the space.

A garage that doubles as a workshop or hobby space should have four to six circuits as a practical starting point. A dedicated 20-amp circuit for lighting keeps your lights on even if you trip a breaker on an outlet circuit with a power tool. Two or three 20-amp circuits for receptacles along different walls give you the ability to run multiple tools without overloading a single circuit. Splitting your receptacles across separate circuits means a table saw on the east wall and a dust collector on the west wall are on independent circuits and will not trip each other. A dedicated 20-amp circuit for a garage refrigerator or chest freezer is also wise because you do not want a tripped breaker from a power tool shutting off your freezer without you noticing.

If you plan to use 240-volt equipment, each piece typically needs its own dedicated circuit. Common 240-volt garage loads and their circuit requirements include an EV charger at 40 to 50 amps on a dedicated circuit, a 240-volt garage heater at 20 to 30 amps on a dedicated circuit, a welder at 30 to 50 amps on a dedicated circuit, and an air compressor over 2 horsepower at 20 to 30 amps on a dedicated circuit. Each of these 240-volt circuits adds to your total circuit count and your sub-panel requirements.

A well-equipped workshop garage typically needs eight to twelve circuits when you account for all the 120-volt and 240-volt loads. This is why a 100-amp sub-panel with 20 to 24 circuit spaces is the standard recommendation for a serious workshop garage rather than a smaller 60-amp panel with 12 spaces.

Here is a practical circuit plan for a two-car workshop garage that covers most needs. Circuit one is a 15-amp lighting circuit for all overhead fixtures. Circuit two is a 20-amp circuit for receptacles along the front wall and garage door opener. Circuit three is a 20-amp circuit for receptacles along the back wall and workbench. Circuit four is a 20-amp circuit for receptacles along the side wall. Circuit five is a 20-amp dedicated circuit for a refrigerator or freezer. Circuit six is a 20-amp or 30-amp 240-volt circuit for a garage heater. Circuit seven is a 40-amp 240-volt circuit for an EV charger. Circuit eight is a 30-amp 240-volt circuit for a welder or large compressor. That gives you eight circuits on a 100-amp sub-panel with room to add more later.

The cost to wire a garage with this level of service in Ottawa, including the sub-panel, all circuits, receptacles, and the ESA permit, runs roughly $4,000 to $7,000 depending on the garage size and the distance from the main panel. Planning all the circuits at once during initial wiring is far more cost-effective than adding circuits one at a time later, because each return visit by an electrician involves a new permit, new inspection, and minimum service charges.

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