TORONTO - All parties in Ontario's legislature agreed in principle Thursday to a private member's bill that would make it mandatory to provide energy ratings to potential home buyers so they can assess the costs of maintaining residences.

The initiative, outlined in a bill introduced by Liberal member Phil McNeely, would be phased in over three years, starting in 2010, and apply to homes and small apartments.

Under Bill 101, a builder or seller would have to get a rating report that informs buyers of the home's energy efficiency to allow them to estimate costs. It wouldn't, however, set limits or regulations on the amount of energy that can be used.

"By measuring the energy rating, consumers will have the choice to weigh energy costs in that important purchase decision," said McNeely, who represents Ottawa-Orleans. "Renters will have the option to also weigh energy costs into their choice.

"Builders of energy-efficient homes will be encouraged to build even better homes. Builders of less energy-efficient homes will have to be open to prospective purchasers."

McNeely said he's encouraged by support he's received from Energy Minister George Smitherman and Natural Resources Minister Donna Cansfield.

Cansfield said about 100 building companies in the province already voluntarily exceed Energy Star ratings, which provide guidelines to make new homes 30 per cent more energy efficient than those that meet minimum provincial building codes.

She called the bill an opportunity to help people choose what sort of home they want to buy.

"We give ratings to our hotels, we even give ratings to the meat we eat," Cansfield said. "Wouldn't it make sense to allow people to have choice and to make sure that when they buy the most important part of the legacy they'll leave maybe to their children, their home, that they know in fact what they are buying?"

Chris Chopik, a real estate agent and instructor for the Toronto Real Estate Board, said if the bill is passed, the real estate community would have a tool to educate prospective buyers about the importance of energy efficiency as costs continue to rise.

"Energy is the second price tag of every house," Chopik said. "The more that we can be doing today to improve the energy resiliency of Ontario homes, the more competitive Ontario will be in the future and the more valuable our housing stock will be."

Similar rules are being implemented in Nova Scotia and British Columbia and are in effect in several U.S. jurisdictions.

Progressive Conservative John O'Toole said his caucus would be supportive, though he went on to call it a "red tape bill," especially with energy-efficiency standards already included in new building regulations coming into force.

Peter Tabuns of the NDP said he was also in favour of the bill, but called for a more aggressive approach from the government to conservation and energy demand management.

"Unless this province changes course and takes the development of a new energy economy as a central pillar in its economic strategy, then it's going to face some very, very rough waters in the years to come," Tabuns said.

The bill will go to committee for further study.