Companies leasing commercial office space will have to disclose the building's energy efficiency rating for the first time from today, in a move designed to make Australia's thousands of brightly lit office blocks use less power.

A star-rating system, similar to that used for electrical appliances, will now be a mandatory part of advertising for lease or sale of office space. The scheme is designed to make climate change a more important consideration in corporate decision-making, in part by naming and shaming companies with office space in energy-hungry buildings.

The star-rating system currently lists the Sydney headquarters of Energy Australia as holding a one-star rating - the lowest possible. Governor Macquarie Tower, home to many state government offices, has a middling performance, with 3.5 stars. At the top end of the scale, The Bond - home to the Barangaroo developer Lend Lease - has a 4.5 star rating, supplemented by the purchase of GreenPower to bump it up to five stars.

The Department of Climate Change and Energy Efficiency hopes the scheme will lead to more companies choosing offices that use power more intelligently. Electricity used to light and air-condition buildings accounts for roughly one-fifth of all the power used in Australia. ''The aim of the scheme is to ensure that credible and meaningful energy efficiency information is given to prospective purchasers and lessees of large commercial office space,'' the department said.

The new ruling applies to most offices with floor space of more than 2000 square metres. For now, leaseholders will only have to provide data about a whole building, but a year from today the rules will be tightened so that an annual review of each separate part of the building must be included.

Analysts said climate change had slowly been climbing the corporate agenda but the new rules amounted to another rung. ''I think there's been a significant gap between what companies have said they have wanted, and what they have eventually gone with in the end,'' said Gavin Gilchrist, managing director of the energy efficiency firm Big Switch Projects.

''There's no question this will raise the profile and appeal of energy efficient, low-carbon office space. I wonder, for example, if the chief executive of BHP Billiton realises his head office in Melbourne is in a building that's a very average three stars, or if the chief executive of Lend Lease knows his Sydney head office only hit five stars by buying GreenPower.''

smh.com.au