Generator Transfer Switch: Ontario Rules, Types and Safe Hookups

A generator can keep the furnace fan, the fridge and a few lights running through a long outage, but only if its power stays inside your house. The part that makes sure of that is the generator transfer switch. It sits between the generator, your panel and the utility supply, and it lets the house draw from one source at a time. Below: what the switch does, why Ontario treats a missing one as a serious hazard, and how the options compare.

What a transfer switch for a generator actually does

Your panel is normally fed by the utility through the meter. When you add a generator, you create a second source that could feed the same wires. A transfer switch for a generator is a selector: in one position the house is connected to the grid, in the other it is connected to the generator, and the design keeps both from being connected together.

The Electrical Safety Authority (ESA) puts it plainly on its generator safety page. A standby generator that is permanently connected to household wiring must have a transfer device, and that device stops generator power from flowing back into the utility system. ESA also tells buyers to look for a recognized certification mark on the generator and its parts, and to buy an approved transfer device or switch with a properly sized connector cord.

Why backfeeding puts line crews at risk

Backfeeding happens when generator power travels out through your service and onto the street. A line that crews expect to be dead can then be live while they repair storm damage.

ESA's January 2026 toolbox talk for contractors calls illegal back-feeding a serious violation of the Ontario Electrical Safety Code that puts utility workers at risk. Its rule is short: never connect a generator to panels, switches or service equipment without an approved transfer mechanism, and limit temporary generator power to approved plug-in loads.

Local utilities say the same thing in their own terms. Oshawa Power's Conditions of Service require a customer with emergency backup generation to make sure it does not back feed into the distribution system in any circumstances. Toronto Hydro's guide to powering up your home says customers must ensure a generator does not back-feed into the grid, whether the unit is portable, standby or emergency.

How to connect a generator to a house without a transfer switch: the honest answer

If you are wondering how to connect a generator to a house without a transfer switch, the honest answer is that you should not wire a generator into the panel, a dryer outlet or any other part of the house wiring without an approved transfer device.

The common shortcut is a cord with a plug on each end, sometimes called a suicide cord, pushed into a receptacle to feed the house backwards. ESA's May 2025 Flash notice on temporary portable generators says it has seen homeowners alter their installations to supply essential loads, and that these changes may cause electrical fires and shock hazards for the people in the building and for utility workers. The same notice allows a portable generator to be used without a transfer device only where there is no possibility of backfeeding the utility lines.

Without a switch, the legitimate option is extension cords, rated for the load, from the generator to the appliances themselves. ESA's Flash also says that once normal power returns, temporary generators must be disconnected and temporary wiring removed, and it strongly advises having any equipment or wiring disturbed for the temporary connection checked. Never connect a generator to wiring or appliances that flood water has reached.

Manual transfer switch for generator hookups

A manual transfer switch for generator use is the usual pairing with a portable unit. An electrician installs the switch beside the panel, moves the circuits you want to back up onto it, and mounts a power inlet on the outside wall. During an outage you start the generator outdoors, plug the cord into the inlet and move the switch to the generator side. When the grid comes back, you reverse the steps. You pick the circuits in advance, and someone has to be home to make the change, but it works with a generator you may already own.

Automatic transfer switch for generator systems

An automatic transfer switch for generator systems is normally paired with a permanently installed standby unit. The switch watches the utility supply, signals the generator to start when the supply drops, moves the load across, and returns it to the grid once utility power is stable. Nobody needs to be home, which matters for a sump pump or a well pump.

Hydro One's emergency backup generation notification form names both choices: the generation facility must have a transfer switch, either a manual transfer switch or an automatic transfer switch, that isolates it from the distribution system. A natural gas or propane standby unit also brings fuel work. A TSSA advisory says residential standby generators up to 26 kW fuelled by natural gas or propane must sit on a firm, level foundation and be installed following the manufacturer's instructions, and the gas connection is work for a gas technician.

Interlock kits and meter base transfer devices

An interlock is a mechanical plate on the panel cover that prevents the main breaker and a dedicated generator breaker from being on at the same time. ESA's code bulletin on grounding generators connected through transfer equipment says a temporary generator feeding part of an existing distribution may be connected through interlocked breakers used as a transfer device. It adds a detail that is easy to miss: in that setup the generator must not have its neutral bonded to its frame, because a second neutral bond downstream of the main service can create objectionable current and weaken ground fault protection. The interlock must also suit your specific panel.

Some utilities also accept a plug-in transfer device mounted at the meter base, so check with yours first. Hydro One says that as of October 1, 2025, every meter base plug-in transfer device installation must be approved by ESA and a connection authorization obtained before reconnection, and that this applies to licensed electrical contractors as well.

What Ontario requires, and who does what

ESA says you must file a notification of work to connect a generator permanently to your home's electrical system, and it strongly recommends hiring a Licensed Electrical Contractor for the installation. Under ESA's do-it-yourself rules, a homeowner may do electrical work in their own home only after filing a notification with ESA, friends, relatives and handymen cannot do it for them, and anyone you hire must hold an ECRA/ESA licence.

The utility usually has a step too. Toronto Hydro asks customers to submit a Service Request for review and approval before any generator connection is installed, then to schedule and complete an ESA safety inspection afterward. Elexicon Energy lists installing a generator or a manual or automatic transfer switch among the routine jobs that need a scheduled isolation, with the electrician, contractor or homeowner on site for the disconnect and reconnect, and it reconnects the service only after ESA issues a Connection Authorization.

So the contractor's side is the load calculation, the switch or interlock, the inlet, the ESA notification, the utility booking and the inspection. The homeowner's side is choosing which loads matter, siting a portable unit safely and running it correctly. Health Canada advises keeping a fuel-burning portable generator at least 6 metres from the house and its doors, windows and vents, never running one in a garage, basement, crawlspace or shed, and keeping carbon monoxide alarms working.

Questions to ask before you buy

Before you buy, work through a short list. Which circuits must stay on: heat, the fridge, a sump or well pump, medical equipment? Is the plan a portable unit with a manual switch or interlock, or a standby unit with an automatic switch? Does your panel have room, and is its rating suited to an interlock? Which utility serves the address, and what does it require before the hookup? Will the contractor file the ESA notification and give you the ESA Certificate of Acceptance once the work passes?

For a whole-home standby system, KV Bear Electrical's published range for a complete installation, covering the generator, transfer switch, electrical work and permitting, is $8,000 to $18,000 (as of October 2026), depending on generator size and how involved the installation is. If your panel is near capacity, a panel upgrade may come first. To plan a transfer switch or standby generator for your home, call 905-999-5048 or request a quote.