How to Run Power to a Detached Garage?

Detached garages, backyard workshops, pool sheds, and in-law suite basements in Ontario homes almost always need more electrical service than a single extension cord across the lawn can provide. Running proper power to a detached structure is one of the largest DIY-adjacent electrical projects a GTA homeowner considers — and one where the details of trenching depth, cable type, and grounding decide whether the install passes ESA inspection. This guide walks Ontario homeowners through how to run power to a detached garage, what the Ontario Electrical Safety Code requires, and how to size the feed.

Short answer: buried feeder from main panel to a garage subpanel with proper grounding at the garage

Direct answer: install a 60-amp or 100-amp subpanel in the garage, feed it via a four-conductor cable (two hots, one neutral, one bond) run in buried PVC conduit or direct-buried NMWU cable, and drive a grounding electrode (ground rod) at the garage for the local bond. Load calc, permit, and inspection at both ends.

Sizing the feeder

• 60-amp subpanel: 6/3 NMWU or 6 AWG copper conductors in conduit. Adequate for lighting, receptacles, a small compressor, and modest tool loads. Most detached garages fit this.
• 100-amp subpanel: 3/3 NMWU or 3 AWG copper. Needed for welders, large heating loads, or workshops with multiple heavy tools.
• Voltage drop consideration: for runs over 30 metres, up-size the conductor to compensate. A 40-metre run at 60 amps on 6 AWG loses over 3% voltage, causing motor performance issues.

Trench and conduit requirements

• PVC conduit burial depth: 450 mm (18 inches) minimum under a walkway or driveway; 600 mm (24 inches) under a road.
• Direct-buried NMWU cable: 900 mm (36 inches) minimum.
• Warning tape: 300 mm above the conduit for identification during future digging.
• Backfill: sand or fine soil around the conduit for 150 mm, then native fill above.
• Locate services first: call Ontario One Call before digging. Free service, mandatory.

Step-by-step: the install

1. Load calculation. Licensed contractor confirms main panel can spare the feeder amperage.
2. ESA permit. File the notification before any physical work.
3. Call Ontario One Call. Free locate service marks buried utilities.
4. Dig the trench. Correct depth for the conduit type. Sloping walls prevent cave-in.
5. Install the conduit. PVC sweep at each end coming out of the ground. Solvent-weld all joints.
6. Pull the feeder cable through the conduit. Lubricant helps on long runs.
7. Install the subpanel in the garage. Mount on plywood backer, flush with drywall or exposed as appropriate.
8. Drive the grounding electrode. 2.4 m (8 ft) ground rod driven into the ground within 3 m of the garage, bonded to the subpanel’s ground bar with 6 AWG copper.
9. Terminate at the main panel. Feeder breaker sized to the feeder amperage. Two hots on the breaker, neutral on the neutral bar, bond on the ground bar.
10. Terminate at the garage subpanel. Two hots on the main lugs or main breaker of the subpanel, neutral and ground on SEPARATE bars (they must not be bonded together at the subpanel).
11. ESA inspection. Inspector reviews both ends before the feeder breaker is energized.
12. Add garage branches. Once the subpanel is live, wire the garage lighting, receptacles, and equipment.

Neutral and ground separation at the subpanel

Direct answer: the neutral bar and ground bar in the garage subpanel must remain electrically separate. Do not bond them together with the removable jumper. Both bars connect back to the main panel via their respective feeder conductors; the local ground rod bonds only to the ground bar.

The Electrical Safety Authority lists bonded-neutral-at-subpanel as one of the most common serious writeups on detached-structure installs. Getting it wrong puts return current on the equipment bond, which becomes a shock risk on any metal object in the garage. Our post on subpanels covers the isolation rule in detail.

Cost expectations for the GTA

• Straightforward 60 A install (short run, easy trench): $2,500-4,000 including permit and inspection.
• Longer run or paved-over trench: $4,000-6,500.
• 100 A install with heavy tool loads: $4,500-7,500.
• Requires panel upgrade at the main: add $3,800-5,500.

What can go wrong

• Skipping the load calc. The main panel may not have capacity for a large subpanel feeder.
• Direct-buried cable at PVC-conduit depth. Insufficient burial fails inspection.
• Missing ground rod. Detached structures require a local grounding electrode.
• Bonded neutral at subpanel. Creates safety hazard and fails inspection.
• No warning tape. Future landscaping strikes the conduit.
• Aluminum feeder conductor without anti-oxidation compound. Corrosion at the terminations over years.

Expert tip from our ESA-licensed electricians

In our experience running power to detached garages across the GTA — particularly to garages that got upgraded for EV charging or a workshop — the single detail that saves the most future cost is over-sizing the conduit at install time. Running 32 mm conduit instead of 25 mm adds $40 to the material bill and lets you pull a bigger feeder in the future without re-trenching. Homeowners who trench once for a 60 A feeder and then need 100 A three years later re-trench the whole yard. Ten dollars of extra conduit up front is the cheapest capacity upgrade in electrical work. Same lesson as the subpanel oversizing our post on subpanels covers.

Related reading from ezsmart.ca

• What is a subpanel?
• Do I need a panel upgrade?
• Install own EV charger?
• Do I need a permit to upgrade panel?
• Add a new circuit

Contact us

Adding power to a detached garage, workshop, or in-law suite in the GTA? Book an ESA-certified electrician to size the feeder, file the permit, and coordinate the trench. Call us at 416-838-9006 or visit our contact page — we will get back to you the same day.