The U.S. Environmental Protection Agency (EPA) today unveiled its annual list of metropolitan areas with the greatest concentration of Energy Star certified buildings. Los Angeles, Washington, D.C., Atlanta, Chicago, and San Francisco led the pack in 2011 with Cincinnati rating last.

Los Angeles has remained the top city from the start of the rankings in 2008. Washington has held onto its number two spot for three years, Atlanta has moved up three spots from 6th place in 2010, and Boston and Riverside edged into the top ten bracket.

“More and more organizations are discovering the value of Energy Star as they work to cut costs and reduce their energy use,” said EPA administrator Lisa Jackson. “This year marked the twentieth anniversary of the Energy Star program, and today Energy Star certified buildings in cities across America are helping to strengthen local economies and protect the planet for decades to come.”

An EPA press release noted that commercial buildings account for nearly 20 percent of U.S. greenhouse gas emissions and that energy waste costs the nation over US$100 billion every year. Energy Start buildings use on average 35% less energy than conventional buildings, the EPA says.

Indeed, even the American National Standards Institute (ANSI) is investigating the need for national energy standards. ANSI announced last month that it would be holding an exploratory meeting on whether to form an energy efficiency standards panel to coordinate the U.S. business community’s approach to energy efficiency. ANSI is known for standardizing everything from hot tubs to computer programming languages.

Here’s the EPA’s rankings for the past four years: