Toronto's CN Tower, usually a bright and colourful beacon on the city's skyline, is seen here dimmed for 2010 Earth Hour Saturday evening. (Cole Burston/Canadian Press)

Ontario saw a four per cent drop in electricity demand Saturday night during Earth Hour, enough to power a city the size of Brampton.

Terry Young of the Independent Electricity System Operator says four per cent might not sound like a lot, but any noticeable drop in demand province-wide is significant.

Canadians joined people in more than 120 countries around the world who flicked off lights at home between 8:30 and 9:30 p.m., attended events illuminated by candlelight or watched iconic landmarks fall dark.

Ontario's Earth Hour decrease this year is compared with six per cent last year and five per cent in 2008.

But, Young says, it doesn't mean Earth Hour necessarily made less of an impact, noting more people likely had heating on this year as it was much colder in Ontario Saturday night than it was last Earth Hour.

Young says Earth Hour is about awareness, and Ontario has seen electricity consumption decrease over the past five or six years.