Because of greater energy efficiency, the EPA estimates carbon dioxide emissions nationwide fell a record 25 billion pounds.

Commercial buildings that have earned the Energy Star use nearly 40% less energy than average buildings and emit 35% less carbon dioxide into the atmosphere. About 500 buildings use 50% less energy than average buildings.

Many of the most efficient commercial and manufacturing buildings are in California. The EPA reports the state is home to 917 of the 4,056 office buildings, schools, hospitals, and public buildings that have earned the Energy Star rating nationwide.

The California properties, which total about 177 million sf of space, save about $199 billion in annual energy costs because of their efficient design and management, the EPA estimates. The buildings also prevent 1.6 billion pounds of greenhouse gas emissions, the equivalent of the output from more than 135,000 vehicles.

The EPA introduced the Energy Star rating in 1992 as a voluntary, market-based partnership to reduce greenhouse gas emissions through energy efficiency. To encourage energy efficient commercial buildings, it offers an on-line energy rating system, Portfolio Manager.

Portfolio Manager is an interactive energy management tool that allows building owners, managers, investors and developers track and assess energy and water consumption. The tool includes greenhouse gas emission factors, which show Energy Star buildings emit an average 35% less carbon dioxide than unrated buildings.

The EPA bases its emissions factors for carbon dioxide on its Emissions & Generation Resource Integrated Database (eGRID), which is consistent with major greenhouse gas reporting protocols. The EPA encourages building owners to use eGRID to compare the CO2 emissions of their buildings with others in their region and across the country. A typical office building in New England contributes 20 pounds of CO2 per sf, while an Energy Star office building in the same area contributes just 15 pounds per sf--a reduction of 25%To find Energy Star commercial buildings in your area, go to http://www.energystar.gov/LabeledList