More homeowners and businesses than ever are replacing their old incandescent holiday lights for efficient LED bulbs, according to Pacific Gas & Electric Co. officials and businesses that sell lighting.

Joe Molica, spokesman for PG&E, said as the public becomes more aware of them, they are becoming more popular. They are trying to raise the awareness that energy efficiency is one of the most important tools we have in the fight against global warming.

According to Molica, because 47 percent of the electricity produced by PG&E comes from the burning of natural gas and 1.6 percent comes from coal, two producers of carbon dioxide. Consequently, the more electricity used, the more carbon dioxide emitted into the atmosphere. While, LEDs are 90 percent more efficient than traditional incandescent Christmas lights, they also last much longer - as long as 20,000 hours compared with about 3,000 hours - and put out less heat, reducing the risk of fire.

Molica said a string of 300 incandescent holiday lights - which is about average - costs the average Bay Area customer $70.40 in energy during the approximately six-week holiday season. That's compared with 43 cents for the same number of LED lights. That means you save $70 a season if you switch out 300 incandescent lights to LED lights.

It is impossible to say how many people have switched, but for the past two years PG&E has been offering exchanges and incentives to residential customers, building owners and merchants to put up energy-efficient lights.

The most dramatic example is at the Embarcadero Center, where more than 17,000 lights illuminate the towers and lure shoppers during the holidays. Boston Properties, which owns the buildings, put in energy-efficient cold cathode technology lights this year, thanks to a $34,000 PG&E rebate. The new lights reduce the energy output from 15 watts to only 2 watts per bulb. It means Boston Properties will save 80,000 kilowatt hours between November and January compared with last year. That's a 43-ton reduction in carbon dioxide wafting into the heavens, Molica said.

During the annual lighting ceremony Nov. 21, PG&E officials handed out 500 strands of LED lights. Many San Francisco merchants jumped aboard the green-lighting bandwagon a year ago.

Fillmore Street merchants switched out their old lights last year. Virtually all the lighting on Fillmore from Geary to Jackson streets is now energy efficient. Mission District and Noe Valley merchants also switched to LED lights last year, Molica said.

More options are also available for consumers. In November, Home Depot offered $3 certificates toward LED lights for people who brought in their incandescent holiday lights. The store also doubled to 30 its selection of kinds of string lights. The store sells 138 eco-friendly yard decor items, artificial trees and other products with energy-efficient lights in them.

"In tough economic times, people still want to celebrate the holidays, so we are trying to make it more affordable to do so," said Kathryn Gallagher, the spokeswoman for Home Depot, which sold 40,000 miles of Christmas lights a year ago, enough to circle the globe 1.5 times. "Green is the trend. We've seen the interest grow and we're expecting to sell more this year. We are trying to educate our customers that they can do simple modifications to their home and save money in the long run. And it's smart business, of course."