EZSMART Corporation, ESA/ECRA #7012690 , North York , Ontario
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Portable generators are how many Ontario homeowners survive multi-day ice-storm outages, and the transfer switch is what turns a portable generator from a driveway noise-maker into a real backup power source for the house. Without a transfer switch, the only option is running extension cords through open windows — which is unsafe, illegal, and misses the whole point of owning the generator. This guide walks GTA homeowners through how to install a transfer switch for a portable generator, what the Ontario Electrical Safety Code requires, and why this is licensed-electrician territory.
Direct answer: transfer switch installation is not homeowner-permitted work in Ontario in most cases. The transfer switch sits directly on the electrical panel bus or on a critical-loads subpanel, and it requires code-compliant back-feed protection to prevent linemen from being electrocuted during an outage. Hire a licensed electrician who will file the ESA notification, install the switch to code, and pass inspection.
Direct answer: a transfer switch is a mechanical or electrical device that lets you switch selected circuits between utility power and generator power. Only one source feeds the circuits at a time — utility OR generator — never both simultaneously. That single-source guarantee is what prevents the generator from back-feeding voltage into the utility grid.
Direct answer: without a transfer switch, a portable generator connected to the home’s wiring will push voltage back up through the utility drop to the transformer on the pole. That transformer steps voltage up from 240 V to primary distribution voltage (7200 V or higher), and any lineman working on the outage-affected feeder assumes it is dead. Back-feed kills linemen. It is one of the reasons the Ontario Electrical Safety Code is strict about generator connections.
The Electrical Safety Authority and every utility in Ontario require code-compliant back-feed protection on any generator that connects to household wiring. Non-compliant installations are a serious writeup on any inspection and a real liability during an outage.
Direct answer: match the transfer switch amperage to the generator output. A 5000 W portable generator at 240 V delivers about 20 A per leg — a 30 A transfer switch or interlock is standard. Larger 7500 W generators need a 50 A configuration. Standby generators over 10 kW need automatic transfer switches sized to service capacity.
Also size the generator to your critical loads with realistic starting-current math. A refrigerator has running load around 200 W but a starting surge of 1500-2000 W. A well pump can spike over 3000 W on start. Our post on breaker sizing for large appliances touches on the starting-current math.
In our experience installing portable-generator transfer setups across the GTA — particularly in Vaughan, Richmond Hill, and rural pockets near Markham — the single detail that improves customer satisfaction most is choosing the right list of critical circuits at install time. Homeowners default to “the fridge and the furnace,” but real ice-storm survival needs more — add the router, one or two bedroom outlets for phone charging, the garage door opener, and a single kitchen counter circuit. Everything else can wait. Get the list right at install and you never wish you had picked differently at 2 am with the wind howling outside. Our post on adding new circuits covers how to consolidate the critical loads onto a well-planned subpanel if the existing layout does not group them well.
Want an ESA-certified electrician to install a portable-generator transfer switch or interlock kit in your GTA home? Call us at 416-838-9006 or visit our contact page — we will get back to you the same day.
Electrician Since 2008 Journeyman Electrician Designated Master Electrician at EZSMART Corp
