Philadelphia City Council on Thursday unanimously approved an ordinance that will require owners of large commercial buildings to report their energy consumption to government under a new system that will "benchmark" properties for efficiency in an effort to spur conservation.

The new rule, sponsored by Councilwoman Blondell Reynolds Brown, requires owners of buildings larger than 50,000 square feet to score their properties according to an Energy Star ranking developed by the U.S. Environmental Protection Agency. Advocates hope the public rankings will provide building owners, as well as prospective buyers and tenants, with comparative energy-efficiency data.

The new rule will go into effect on June 1, 2013, and be administered by the city's Office of Sustainability. Failure to comply would be punishable by a $300 fine for the first 30 days and then $100 a day.