Generator Transfer Switch Explained for Toronto Homes

This Guide explains in plain terms what transfer equipment does, how the common options differ at a high level, and how the ESA permit fits. It isn't a buying guide and doesn't recommend brands.

If you're still deciding on the generator itself, start with Standby vs Portable Generators in the GTA.

What a Transfer Switch Does

Your home normally gets power from the utility. A generator is a second power source. Transfer equipment sits between the two and makes sure only one source feeds your home's circuits at a time.

That matters for two reasons:

• It prevents backfeed. ESA explains that a transfer device prevents generator power from flowing back into the utility system. Backfeed can put utility crews working on lines at risk.
• It protects your home and equipment when the utility power comes back while the generator is running.

ESA's guidance is that standby generators permanently connected to your electrical wiring must have a transfer device, and that a notification of work must be filed with ESA to connect a generator permanently to a home's electrical system.

The Common Types, at a High Level

There are a few general approaches to transfer equipment. Which one suits your home depends on the generator, the panel, the loads you want to back up and what is approved for your installation. Your licensed electrician confirms the right option.

Automatic transfer switch (ATS)

An automatic transfer switch is usually paired with a permanently installed standby generator. When it senses that utility power is gone, it signals the generator and switches the selected circuits over. When utility power returns, it switches back. The homeowner doesn't have to move anything by hand.

Manual transfer switch

A manual transfer switch is often paired with a portable generator. The generator plugs into a connection point that has been installed for it, and a person moves the switch to change the power source. ESA's January 2026 contractor guidance lists portable generators paired with a manual transfer switch as one of the safe standby power options, when planned with a Licensed Electrical Contractor.

Interlock

An interlock is a mechanical device fitted to an electrical panel. It physically prevents the main breaker and the generator breaker from being on at the same time, so only one source can feed the panel. Like a transfer switch, it has to be an approved device installed as part of a permitted job.

Which is "better"?

There's no single answer. Some homeowners want automatic switching with a standby unit. Others prefer a portable generator with manual switching. The right choice depends on your home, your panel and what you want to keep running.

Whole-Home vs Selected Circuits

Transfer equipment can be set up to back up selected circuits, such as a furnace, a sump pump, a fridge and some lighting, or a larger portion of the home. That decision connects to generator size and to your panel.

If you're not sure your panel or service has room, see 100 Amp vs 200 Amp Service: What Toronto Homeowners Need to Know. Our Planning a Home Generator Install Guide covers the wider planning steps, from location to load list.

What Not to Do

ESA is clear that a generator must never be connected to panels, switches or service equipment without an approved transfer mechanism. Improvised connections, such as back-feeding through a receptacle, are dangerous to you, your family, your neighbours and utility workers.

ESA also reminds homeowners to only use generators and accessories that carry a recognized certification mark, and to never run a generator inside a home or garage.

Please don't wire a generator into your home yourself. Transfer equipment is installed by a Licensed Electrical Contractor with an ESA permit.

The ESA Permit and Inspection

Connecting a generator permanently to your home's wiring needs a notification of work with ESA, according to ESA's generator safety guidance. We take out the ESA permit and arrange the inspection.

When the work is accepted, ask for the ESA Certificate of Acceptance and keep it with your home records.

Where Toronto Hydro Fits

Transfer equipment is on your side of the meter. Its job is to keep generator power off the utility system. Toronto Hydro's own equipment and steps stay with Toronto Hydro.

Questions to Bring to Your Quote

• What do you want to keep running? (Make a list.)
• Do you already have a generator, or are you choosing one?
• Where would a standby unit or a portable generator connection go?
• How much space is in your panel?
• Are there other plans, such as an EV charger or heat pump, that affect capacity?

Electro Group Ltd. holds ESA Licence #7017939.

Next Steps

Planning backup power for a home in Toronto or the GTA?

• Request a free quote
• Call 289-814-7241

Tell us your city, home type, generator plans and the circuits you care about most. We'll explain the transfer options for your home and take out the ESA permit.

Electro Group Ltd. · Toronto and the GTA · 289-814-7241 · ESA Licence #7017939

FAQ

Do I need a transfer switch for a generator?
ESA says standby generators permanently connected to a home's wiring must have a transfer device. Never connect a generator to your panel or wiring without an approved transfer mechanism.

What's the difference between a transfer switch and an interlock?
Both keep the generator and the utility from feeding your home at the same time. A transfer switch is a separate device that switches circuits between sources. An interlock is a mechanical device on the panel that stops the main and generator breakers from being on together.

Is an automatic transfer switch only for standby generators?
Automatic transfer switches are typically paired with permanently installed standby generators. Portable generators are more often paired with manual switching.

Does a generator connection need an ESA permit?
Yes, connecting a generator permanently to your home's electrical system needs a notification of work with ESA. We take out the ESA permit and arrange the inspection.

How much does a transfer switch cost?
It depends on your home, panel and generator. We don't publish prices.