Owners of large commercial buildings in Philadelphia will be required to report their energy consumption to city government under a new system that would rank buildings for efficiency in an effort to spur conservation.

The Philadelphia City Council appears set to approve an ordinance on Thursday that would require owners of buildings larger than 50,000 square feet to report their energy and water consumption under a scheme that gives the building a green score.

The Building Owners' and Managers' Association of Philadelphia (BOMA), which calls the proposal "well intentioned," objects to the law's requirement that the green scores be publicly disclosed online. It says a building may score low because of the behavior of energy-intensive tenant.

"The bill could easily and unjustifiably apply a `scarlet letter' to a building," Doug Hoffman, BOMA's chairman, testified on June 5 to council's environment committee. BOMA wants the city to keep the energy data confidential, disclosed only to prospective buyers or tenants.

Councilwoman Blondell Reynolds Brown, the bill's sponsor, says that public disclosure is an integral part of the process.

"It's important for consumers to know," she said Monday. "For those of us who are conscientious about being sustainable, we may make judgments about where we want to conduct business."

Conservation advocates support the benchmarking proposal, which they say will provide building owners and tenants with comparative information. They compare the rankings to nutritional labels on food and fuel economy ratings on vehicles.

"The assumption is that disclosure will help empower owners, tenants, investors and banks to identify and compare the energy performance of buildings, unlocking the market's ability to drive demand and competition for energy-efficient space by giving it full value through transparency," said Laurie Actman, deputy director of Energy Efficient Buildings Hub, the federally funded project run by Pennsylvania State University at The Navy Yard.

The score is based upon standardized efficiency rankings developed by the U.S. Environmental Protection Agency, which developed the Portfolio Manager benchmarking tool. That tool that is currently used to determine if a building deserves the Energy Star rating — a score of 75 or higher on a zero-to-100 scale. More than 183,500 buildings nationwide were enrolled in the program last year, according to Energy Star.

Reynolds Brown said the new rule, which would go into effect on June 1, 2013, was modeled on laws enacted in recent years in New York, San Francisco and Washington.

Failure to comply with the Philadelphia law would be punishable by a $300 fine for the first 30 days and then $100 a day.

The proposal initially would have applied to buildings of 25,000 square feet, but the threshold was doubled to make sure the city's Office of Sustainability could manage the data, Reynolds Brown said. She did not know how many buildings would be affected. A 50,000-square-foot building is slightly larger than a typical Best Buy store.

"At some hour we can revisit it to bring smaller buildings into the fold when we see if it's manageable," she said.