How much does it cost to install a 100-amp sub-panel in a detached garage in Ottawa?

Installing a 100-amp sub-panel in a detached garage in Ottawa typically runs between $2,500 and $5,500, though the final number depends heavily on how far your garage sits from the main panel and whether you need to trench underground or can run overhead service.

The sub-panel itself costs between $300 and $600 for a quality 20- to 24-circuit panel from brands like Square D or Eaton. The bulk of the cost comes from labour, the copper wire run, conduit, and the ESA permit and inspection fees. For a garage that sits 15 to 25 metres from the house, most Ottawa electricians quote in the $3,000 to $4,500 range with everything included.

If your detached garage is within about 10 metres and you already have a clear path for conduit, you might land closer to $2,500. On the other hand, garages that are 30 metres or more from the main panel push costs toward $5,000 or beyond because copper wire at that gauge is expensive by the metre and longer runs may require upsizing wire to compensate for voltage drop.

The ESA permit for a sub-panel installation in Ontario is mandatory. Your electrician files the permit application, and the ESA inspector visits after the rough-in stage and again after final connections. The permit fee itself runs around $150 to $250 depending on the scope. Only an ESA-licensed electrical contractor can pull this permit, and the work must meet the Ontario Electrical Safety Code.

One factor Ottawa homeowners often overlook is the capacity of their existing main panel. If your house panel is already a 100-amp service, you cannot simply add a 100-amp sub-panel without upgrading the main service to 200 amps. That upgrade alone adds $2,000 to $4,000 to the project. Most homes built after the mid-1990s in Ottawa already have 200-amp service, so this is mainly a concern for older neighbourhoods like the Glebe, Westboro, or Alta Vista where original electrical may not have been upgraded.

For the underground run, your electrician will bury approved conduit at least 600 millimetres deep as required by code. The trench work can be done by hand for short runs but usually requires a small trencher for longer distances, adding $500 to $1,200 depending on soil conditions and landscaping that needs to be restored afterward.

What Size Sub-Panel Should You Choose

A 100-amp sub-panel gives you plenty of room for general garage use including lighting, outlets, a small compressor, and even a future EV charger. If you plan to heat the garage with a 240-volt heater or run heavy woodworking equipment, 100 amps is the right choice. For a garage that only needs lights and a few outlets, a 60-amp sub-panel at $1,800 to $3,200 can save you money while still meeting most needs.

Get at least two quotes from licensed Ottawa electricians and confirm the quote includes the ESA permit, inspection coordination, trenching, backfill, and panel termination at both ends. Some quotes only cover the panel installation and list the trench as an extra, which creates sticker shock later.

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