Homes and businesses in Chicago will turn out their lights tomorrow night in an effort to raise awareness about climate change. But it’s more symbolic than anything else.

If you turn out your lights for Earth Hour, you might save a nickel. Com Ed spokesman John Dewey says the company encourages Chicago residents to participate. And he says Earth Hour won’t have a significant impact on Com Ed’s bottom line.

DEWEY: If a customer were to turn off 8 of their lights over the course of an hour they would save about 500 watts over the course of that hour or half of a kilowatt hour. And while this is not a large amount, it’s an educational effort.

Earth Hour is a global campaign created by the World Wildlife Fund. It started last year in Sydney, Australia where over 2 million people participated. Dozens of cities around the world are expected to join Chicago in tomorrow’s hour of darkness. Lights go out starting at 8 p.m.