TORONTO - Many Canadians from coast to coast were powering down Saturday for the sixth Earth Hour, as the organization behind the global campaign expressed hope that the event will keep gaining momentum in years to come.

"We didn't really know how it would go when it first started, but each year we have more and more countries and cities and communities join on," said Zoe Caron, a spokeswoman for the World Wildlife Fund's Canadian operations.

"I think as long as it's serving its purpose of giving people an outlet to talk about climate change and show that they care... then it will continue to be a success," she said.

"It will go on as long as people keep caring about it."

It was unclear how many people would take part in this year's event. The Independent Electricity System Operator, which helps manage and coordinates Ontario's power grid, said electricity demand was down 2.7 per cent from a typical Saturday night.

Some 150 countries signed up for the annual event, which urges people to turn off the lights between 8:30 p.m. and 9:30 p.m. local time. That's compared with 135 last year, the organization said.

In Canada, 511 municipalities promised to take part, with utilities throwing their support behind the campaign.

B.C. Hydro made a pitch on its website, urging consumers to join in and also make plans to reduce energy use year around. Last year's response shows what people can do, the utility said on its website.

"British Columbians turned off the equivalent of 7.8 million 15-watt compact fluorescent light bulbs for the hour," the utility said. "If everyone in B.C. implemented the same conservation measures for just one hour every evening, the combined savings would be enough to power close to 4,000 homes for an entire year."

Ontario electricity provider Hydro One said it would mark Earth Hour by turning off non-essential electrical equipment at its office facilities across the province.

A couple of candlelight walks are planned for Toronto and some hotels are planning to turn off their lights for the hour and have candlelight dinners or candlelight swims.

Hockey fans taking in Saturday night's NHL games in Vancouver and Toronto might notice the lighting is a bit dimmer than normal. The league says non-essential lighting will be turned off for an hour at all games scheduled for Saturday night and the league's New York City headquarters will also observe Earth Hour.

Last year in Canada there was some concern that fewer people may have been observing Earth Hour compared to previous years. Disappointment was expressed in Toronto when many stores stayed brightly lit and there were few public celebrations compared to previous years.

Events were taking place across the world and Australians were among the first to mark Earth Hour with Sydney's iconic Harbour Bridge and Opera House going dark Saturday night.

• EARTH HOUR IN TORONTO
• EARTH HOUR IN MONTREAL
• THE TAIPEI 101 BUILDING
• EARTH HOUR IN PARIS
• Earth Hour In Berlin
• Lights Out For Earth Hour 2012 in London
• Sri Lankan President Mahinda Rajapakse l
• EARTH HOUR IN MOSCOW
• EARTH HOUR IN ISLAMABAD
• EARTH HOUR IN SYDNEY