At least 10,000 people showed up at Nathan Phillips Square to show solidarity with Earth Hour and hear Canadian pop star Nelly Furtado.

And the first song sung Saturday night by Canada's Earth Hour ambassador? "Turn Out The Light" -- played acoustically as many in the crowd held candles.

The city's downtown skyline darkened from 8 p.m. to 9 p.m. in response to the global event.

Toronto Mayor David Miller said he's thrilled to see so many residents and businesses excited about taking part in the city's first ever Earth Hour event.

"There's been an incredible outpouring of enthusiasm," Miller told CTV Newsnet on Saturday afternoon.

"People are doing things in their own houses, in their neighbourhoods, so we know that engaging people directly in their own communities to fight climate change and to have some fun at the same time is a good strategy."

City officials hoped one million residents will turn off or dim their lights between 8 and 9 p.m. for the World Wildlife Fund eco-initiative that began in Sydney, Australia on March 29, 2007.

Toronto Hydro expects to see a five per cent drop in electricity use during the hour.

"In a five per cent drop, we could remove about 100,000 homes from the grid," said spokeswoman Denise Attallah.

Toronto is one of about 150 communities across Canada taking part, making the country one of the strongest supporters of the plan worldwide.

Residents will be lighting candles inside their homes, and most businesses in Toronto's downtown will shut off or dim their lights.

Miller said it's too early to determine if Earth Hour will be an annual event in the city, but he says the initiative will have long-term effects.

"I think what Earth Hour is showing is that Canadians are ready and they understand it's not always about serious things when you fight against climate change -- you can have a lot of fun at the same time," he said.

The mayor says Toronto has been a world leader for 20 years with its conservation programs, which includes energy retrofits, aggressive targets to reduce greenhouse gases, green city and transit vehicles, and a recent bylaw that allows homeowners and businesses to generate their own environmentally sustainable electricity through methods such as installing solar power panels.

With a report from CTV Toronto's Ken Regular