A primary object of Earth Hour is to provide a global show of force leading up to December meetings in Copenhagen, Denmark, on drafting a new global-warming treaty.

Earth Hour is not without its critics, who say long-term behavior changes are needed more than one-time attention-getters and that the manpower and cost — particularly of municipal and corporate employees — to go around and manually override automatic switches at locations throughout a city or business location is counterproductive.

And following the inaugural "Lights Out Utah" campaign in 2007, Rocky Mountain Power officials — while supportive of that and future conservation efforts — reported at the time as seeing no significant decrease in power consumption during the hourlong project.

They cited a 10-degree jump in the mid-September evening's temperature as likely resulting in many homes and businesses using extra power for air conditioning, adding that lighting accounts for only 14 percent of average residential power use, with refrigeration and air conditioning comprising on average more than 50 percent.

Contributing: Aaron Falk

E-mail: taylor@desnews.com