ALL Australian homes will soon have to undergo a mandatory energy-efficiency assessment costing up to $1500 per property.

The assessment has to be done before any property can be sold or rented under new laws to tackle carbon emissions.

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The mandatory assessment - being drafted into law by the federal and state governments - will rate homes by an energy efficiency star system, similar to the ratings given to fridges and washing machines.

It will apply to all commercial properties from later this year and to all residential properties from May 2011, Adelaide Now reports.

A spokesman for State Energy Minister Pat Conlon said the ratings would inform prospective owners or tenants of a building's energy use, so they could factor it in to their buying or rental decision.

The spokesman said details of the "Mandatory Disclosure" scheme - including who would carry out the assessments and how much they would cost - were yet to be decided.

Energy efficiency expert Arthur Grammatopoulos, of Helica Architecture, said rating properties could cost up to $1500 a house.

"I think this is a positive move for the industry but the question has to be asked, will there be enough experts to cope with demand when the law is introduced?" he said.

A similar scheme with a six-star rating has been operating in the Australian Capital Territory's property market for several years.

Queensland's State Government introduced a mandatory Sustainability Declaration form on January 1, requiring homeowners to declare their property's green credentials to prospective buyers or risk a $2000 fine.

Mandatory disclosure has been criticised by property experts as an unwarranted expense that will not influence purchasing decisions or cut household pollution.

The Real Estate Institute of SA said governments were playing environmentally "popular politics" by introducing a law that they say will simply add to the cost of selling and renting a home.

"I think they are patronising people who are making the biggest purchase decision of their life by thinking a rating system will influence that decision," REISA chief executive Greg Troughton said.

"It's already hard enough to buy and sell a home and this is just another financial impost that also has the potential to delay the sale of a property."

While Mr Troughton said vendors would bear the cost of having their home rated by a licensed expert, independent SA MLC and former Valuer-General John Darley said landlords would look to pass the cost on to tenants.

"This will be an extra cost to working families who have to rent because they can't afford a mortgage," he said.

"And we need this like a hole in the head unless the governments can convince us there is a definite benefit, like a reduction in household pollution."

The Council of Australian Government's National Strategy on Energy Efficiency says Mandatory Disclosure will "help households and businesses prepare for the introduction of the Carbon Pollution Reduction Scheme".