I was surprised to hear Ken Shaw reveal on CTV's noon newscast that Toronto Hydro asked the company to disconnect itself from the grid and operate on its own generators for the day, in anticipation of extremely high electricity demand during the heatwave. 

Their Agincourt plant has the ability to be self sustaining for a time in the event of an outage, but this is the first time I've ever heard of a company - especially an over-the-air TV station that admittedly uses a massive amount of wattage every day - adhering to a request to operate on its power. 

It's not immediately clear how long they have to be using the generators or how long they're good for. But what happens if there's an actual power failure and CTV's ability to stay on back-up is reduced because they're already on it?

I was working in a TV newsroom back in 2003, when a large part of Ontario and the eastern part of the U.S. went dark for hours and days. We went to emergency power, too, but only because there was no other choice. This is the only time I've heard of a TV station being asked to voluntarily pull its own plug.

Has this ever happened before?