What size breaker do I need for an EV charger?

The breaker is sized from the charger setting, then derated for continuous load

Use the charger’s commissioned amperage first. The correct EV charger breaker size is not chosen by guessing, by copying a neighbour’s setup, or by installing the largest breaker that fits in the panel. It starts with the EVSE nameplate and the output current the electrician sets during commissioning.

EV charging is treated as a continuous load because the car can draw power for hours. In practical terms, the charging current is limited to about 80% of the breaker rating. Said another way, the branch circuit is sized at 125% of the selected charging current.

Examples, assuming the charger is approved for that setting and the rest of the installation passes the load calculation:

That table is not permission to install a breaker. It is the sizing logic. The breaker also has to match the conductor, the termination ratings, the charger instructions, and the available capacity in the electrical service.

Many Level 2 chargers can be set lower than their maximum. That setting may be made with internal DIP switches, a commissioning app, or an installer-only software limit. The breaker is then selected for that fixed output, not for a future “maybe” setting. If the charger is later reconfigured to a higher amperage, the circuit has to be checked again.

For a complete installation, see our EV charger installation service. If your existing charger is already installed and the breaker trips while charging, that is a different problem from sizing and is covered here: why an EV charger trips the breaker.

The wire has to match the breaker, the installation method, and the charger terminals

The breaker protects the wire, so the wire size must be chosen before the breaker is finalized. Oversizing a breaker to “stop nuisance trips” is unsafe because it can let the conductor overheat before the breaker opens.

For an EV circuit, conductor sizing is affected by more than the printed amperage on the breaker:

• copper or aluminum conductor type
• insulation temperature rating
• whether the wiring is in cable, conduit, armoured cable, or buried raceway
• number of current-carrying conductors in the raceway
• ambient temperature, especially in garages and outdoor conduit runs
• voltage drop on long runs from a basement panel to a detached garage
• the terminal ratings on the breaker and the EV charger
• whether the EVSE is hardwired or cord-and-plug connected

A common mistake is treating the breaker, receptacle, and cable as interchangeable parts. They are not. A receptacle may have one rating, the charger cord another, and the EVSE output setting another. The installation has to satisfy all of them at the same time.

Hardwired chargers remove some receptacle-related failure points, but they still require the correct breaker and conductor. Plug-in chargers need the correct receptacle, box, cover if required, mounting height, and a circuit that is not shared with garage outlets, freezers, tools, or lighting.

The panel directory should also be updated. An EV circuit should be clearly identified, especially where the charger has been deliberately limited to a lower output. That prevents a later owner, tenant, or handyman from assuming the breaker can be changed without recalculating the circuit.

For comparison, dryer, range, and hot tub circuits are also large dedicated loads, but they are not sized the same way as an adjustable EVSE. See dryer breaker sizing, stove breaker sizing, and hot tub breaker sizing for those specific appliances.

Panel capacity can be the limiting factor even when there is physical space

A spare breaker space does not mean the panel can supply the EV charger. Before adding an EV circuit, the electrician needs to do a load calculation for the home and service. That calculation is what decides whether the service has enough capacity for the charger setting you want.

The load calculation looks at the service size and the major existing loads, such as:

• electric range, wall oven, cooktop, or dryer
• air conditioning, heat pump, or electric space heating
• hot tub, sauna, pool equipment, or workshop equipment
• basement apartment loads, second laundry, or second kitchen
• existing subpanels and garage loads
• the proposed EV charger output

This is where many 100A homes need a careful decision. Some homes can support Level 2 charging at a lower setting, especially where the house has gas appliances and modest electrical demand. Other homes are already tight before the EV is added.

Lower-amperage charging can be the right answer. A charger set to 16A or 24A may still recover a normal daily commute overnight, while placing far less demand on the service than a high-output setting. The best amperage is the lowest setting that reliably meets your driving pattern, not automatically the highest setting the charger can advertise.

If capacity is tight, there are three common options:

• set the charger to a lower fixed output
• install an approved load-management device so the charger reduces or stops charging when the home load is high
• upgrade the service and panel, often to 200A where the utility and installation conditions allow it

A load-management device can often avoid a panel upgrade where the issue is peak demand rather than breaker space. If a service upgrade is necessary, a 100A-to-200A panel upgrade in the GTA typically falls in the $3,200–$4,500 range including the ESA permit and inspection.

For the EV charger itself, many GTA homeowners land between $1,500 and $3,000 all-in, depending on the wire route, panel capacity, wall finishes, and whether load management is needed.

An ESA notification is required for a new EV charger circuit where electrical work is done

A new EV charger branch circuit is not a plug-and-hope project. In Ontario, new electrical work of this kind requires an ESA notification where applicable, and the installation must be done under the Ontario Electrical Safety Code.

City Power Electrical Services is a Licensed Electrical Contractor, ECRA/ESA #7015314, and for EV charger work we file the ESA notification where required, install to the approved charger instructions, and leave the circuit ready for inspection.

The ESA inspection is not just a look at the charger on the wall. The inspector may check the parts of the installation that prove the circuit is safe, including:

• breaker type, rating, and panel compatibility
• conductor size and wiring method
• grounding and bonding continuity
• torque and termination quality where visible or documented
• receptacle or hardwired connection method
• weatherproofing for outdoor installations
• labelling and panel directory
• load calculation or load-management details where capacity is a concern

If the charger is installed in a garage, on an exterior wall, or near a driveway, the physical installation matters too. The cable needs protection from damage, the EVSE must be mounted securely, and outdoor equipment must be rated for the location. A charger mounted outside also has to be positioned so the cord reaches the vehicle without becoming a trip hazard or crossing a public sidewalk.

The utility may also be involved if the service is being upgraded. In Toronto and the GTA, that can mean coordination with Toronto Hydro, Alectra, Hydro One, Elexicon, Oshawa Power, or another local distributor, depending on the property. A standard charger circuit usually does not require utility work, but a service upgrade does.

The safest answer is a matched system, not a bigger breaker

The right EV charger breaker size is the one that matches four things at once: the charger output, the conductor, the panel capacity, and the ESA-approved installation. If one of those does not match, the breaker size is wrong.

Do not increase a breaker because charging is slow. Charging speed is set by the EVSE output and the car’s onboard charger, not by wishful breaker sizing. Do not install a high-output charger just because the panel has two open spaces. And do not assume a receptacle is EV-ready because it physically accepts the plug.

A proper EV charger installation should leave you with:

• a dedicated 240V circuit sized for the charger’s configured output
• conductors selected for the breaker and wiring method
• a confirmed load calculation or approved load-management plan
• an ESA notification and inspection where required
• a labelled breaker and a charger setting that cannot be casually increased

If you are still comparing charger sizes, start with your real driving need: kilometres per day, parking time, and whether you can use Ontario overnight rates. Then size the circuit to that need. In many homes, a moderate Level 2 setting is faster than necessary and much easier to fit safely than the maximum output printed on the box.

For more electrical safety answers, visit our electrical answers hub.