The initiative began in Sydney in 2007 but 12 years later, is it really as powerful as it once was?
Earth Hour - the annual event where people are encouraged to turn off lights and devices for one hour as part of a call for action against climate change - rolls around Saturday evening.
But as 180 nations continue to participate at 8:30 p.m. local time the last (or second-to-last) Saturday of March, it appears to be losing steam in Toronto and the GTA.
Elsewhere, such as in Hong Kong, major buildings along Victoria Harbour turned off their non-essential lights at 8:30 p.m., and the city's popular tourist attraction known as the Symphony of Lights was cancelled.
In Taipei, Taiwan's capital, the island's tallest building, Taipei 101, joined surrounding buildings in shutting off the lights.
And in Paris, Mayor Anne Hidalgo dimmed the lights Saturday on the city's most famous monument - the Eiffel Tower - for an hour.
We can expect something similar when the clock strikes 8:30 p.m. in Toronto, with the CN Tower dimming its lights.
But with Earth Hour now in its 12th year in Canada, how much do Canadians actually care about this anymore?
"Last year, Toronto Hydro stopped reporting a load drop during Earth Hour because we were no longer seeing much participation," Toronto Hydro's Christina Basil told NEWSTALK1010 by email.
"In 2017 - the last year we reported the drop - we saw a 2 per cent decrease in demand," she added.
And while 2 per cent is such a small number that it can't even be positively linked to Earth Hour itself, it's still a higher number than in other parts of the GTA.
Shortly after Earth Hour concluded in 2018, the CBC reported a 1.5 per cent drop in electricity usage across regions served by Alectra Utilities at the north end of the GTA and beyond. The city of Barrie was even less, at 0.9 per cent.
Elsewhere in Canada, B.C. saw a rise in power consumption from 8:30 to 9:30 p.m., according to the CBC.
But Basil says, those numbers aren't necessarily representative of a negative trend.
"The good news is that we know Torontonians are adopting conservation into their everyday lives," she explained. "That may be part of the reason that participation in Earth Hour is waning."
- With files from the Canadian Press