IT'S A RACE in reverse, you might say.

Mayor Nutter yesterday announced the launch of a citywide competition among big buildings to show the lowest energy costs, with a national prize awaiting the winners after a year.

The Energy Reduction Race will tally the energy bills of the participating commercial skyscrapers in the city and will be judged by the U.S. Department of Energy and the Environmental Protection Agency.

The "race" ends Sept. 30, 2015, when each of three top-performing buildings will be awarded $5,000. There's a consolation prize for those who signed up but didn't win - free building-operator training to help meet the overall 5 percent energy-reduction goal.

Nutter also unveiled the results of the city's Energy Benchmarking Report, which summarized findings from the second year of the Philadelphia benchmarking program. Put in motion in 2012, the program was spawned from Philadelphia's energy- and benchmarking-disclosure law, which requires large, nonresidential buildings 50,000 square feet and up to report electric and water use to the city annually.

"The benchmarking data demonstrates that, overall, Philadelphia's large commercial buildings perform above the national average when it comes to energy efficiency," Nutter said.

"Energy efficiency can, in fact, become a competitive business advantage here in Philadelphia. This is real money, real savings, doubling the bottom line."

According to the report, more than 90 percent of the buildings covered by the law represented roughly one-quarter of the city's total building-floor area.

Shawn Garvin, regional administrator for the EPA's mid-Atlantic region, said he's not averse to competition among cities for a challenge like the Energy Reduction Race.

"I've been known to create competition between mayors," he quipped.

"Your city is off to a terrific start in this competition, [with] 210 Energy Star-certified buildings."

Philly also will participate in the Energy Department's Better Buildings Challenge, a 10-year commitment to reduce building-energy use by 20 percent or more.