Sydney- The Australian progenitors of Earth Hour said Sunday they were thrilled their lights-off initiative had been taken up by millions of householders and businesses around the world.

New Zealand's Christchurch was the first big city to kick off Earth Hour on Saturday as lights were shut off for an hour to raise awareness that generating electricity from coal and oil is a big contributor to the greenhouse gases that are causing climate change.

It continued its westward progress through Sydney, where the normally glowing Harbour Bridge and Opera House faded to black for 60 minutes, and on to Asia, Europe and North America.

Lights guttered across 14 time zones, the last to go the United States west coast where San Francisco's Golden Gate Bridge lost its illuminations.

"When people act together it's the aggregate of their actions that start to make a difference," said World Wide Fund for Nature (WWF) spokesman Andy Ridley.

"Even one hour," he said, "it's so tiny, but when you add it all up together and imagine we were able to do that a lot more hours of the day, through the whole year, that's when we start breaking into really serious emission cuts."

WWF staged the first Earth Hour in Sydney last year and has managed to turn it into a global initiative with people in 35 countries agreeing to flick the switch for an hour.

Electricity generating company Energy Australia reported a drop in power consumption of 8.4 per cent in Sydney's city centre over Earth Hour - sharply down on last year's
10.2 per cent despite a doubling in the number of registered participants.

WWF chief executive Greg Bourne could not explain the disappointing outcome.

"It's less to do with the drop but the beginnings of the behavioural change," Bourne said.

Hollywood actor Cate Blanchett, director of the Sydney Theatre Company, described Earth Hour as a "grand gesture."

Blanchett brought forward the start of Saturday's theatrical performance by 90 minutes so the audience could attend a glittering Earth Hour gala at a restaurant overlooking the harbour that was illuminated by hundreds of candles.

"It's fantastic that an idea as potent as Earth Hour came out of Sydney," the globetrotting Oscar-winner said.

Other restaurants jumped on the bandwagon too, advertising lavish Valentine's Day-style candlelit Earth Hour dinners.

Critics of the initiative claimed the spread of Earth Hour theme parties in Australian cities was gobbling up the savings from turning off the lights on public buildings.

A WWF-commissioned poll of 3,000 Australian householders had 58 per cent saying they turned off lights during Earth Hour and 46 per cent saying they had unplugged other electrical appliances. (dpa)