Short answer: A detached back-alley garage may have been wired only for lighting, a door opener and a block heater. Before committing to trenching or a service upgrade, check what already supplies the garage and how much charging your driving routine needs while the vehicle is parked.
Can my existing detached-garage wiring support an EV charger?
A single 15A or 20A, 120V branch circuit is a different starting point from a 240V feeder serving a garage subpanel. The electrician checks the actual wiring, protection, voltage, condition and other garage loads. The rating printed on a subpanel does not tell you how much power its feeder can supply.
A subpanel is a practical way to distribute a suitable garage supply among charging, lighting and other circuits. Adding one alone does not increase feeder or house-service capacity.
Where the existing feeder has enough assessed capacity, modest Level 2 charging may be sufficient. At 240V, 16A provides roughly 3.8 kW and 24A roughly 5.8 kW, compared with about 1.4 kW for 120V charging at 12A. Those are electrical input comparisons, not guaranteed battery recovery: vehicle limits, losses and winter battery conditioning affect results.
Discuss consecutive driving days and overnight parking time in our Level 1 or Level 2 guide for Edmonton homes.
When is a new underground wiring route and trenching needed?
If the existing supply cannot support the proposed charger and garage loads, a new or upgraded wiring route may be needed. Existing conduit may be reusable only after its condition, size, route and suitability are checked.
Planning starts at the house supply and follows a feasible route to the garage. Distance, decks, concrete walkways, fences, mature trees, underground utilities and entry points all affect the work. Utility locating and any private-service locating must be addressed before excavation.
Burial requirements depend on the wiring method, surface and physical protection under the applicable code. Inspection stages must be planned before covering underground work. See our permit and inspection guide.
Revolt backfills the trench. Landscaping, sod, concrete, paving and other surface restoration are excluded unless specifically agreed in writing. Confirm those boundaries, the garage subpanel and any feeder work in the quote.
Our detached-garage EV charger installation page explains the service in more detail.
How does a 100-amp house panel affect a detached-garage charger?
There are two separate capacity questions: can the house service support the charging load, and can the supply to the garage carry that load alongside its other circuits? A larger garage feeder does not increase the house service, and spare breaker spaces do not establish spare electrical capacity.
A service load calculation, a suitable charging rate and, where appropriate, Canadian-approved EV energy management can help establish the options. EVEMS must address the relevant supply limits; managing only the house service does not automatically protect an undersized garage feeder.
For the service question, read Can you charge an EV on a 100-amp service? For the overall installation journey, visit home EV charger installation in Edmonton.
How to prepare for a detached-garage charging review
- Your vehicle model and year, or what you are considering.
- Approximate distance between the house and garage and where you normally park.
- Whether the garage has a subpanel, and any known feeder details—“not sure” is fine.
- Photos of the house panel, garage electrical equipment, charger location and yard route.
- Other garage loads and future plans, such as tools or heating.
You can start without photos or a confirmed charger model. For connector choices, read our NACS and J1772 charging guide; for scope comparisons, read what affects installation cost.
Capacity background: EPCOR’s home EV charging guidance.
For panel photos, open only the outer door if it is safe to do so. Leave the inner protective cover in place, never touch wiring, and skip the photo if access appears damaged or unsafe.
Final equipment suitability, charging output and pricing depend on assessment of your property and an agreed written scope. An article or panel photo cannot confirm the installation design.