Opera House: bold, beautiful and green

It's already the star of the harbour, and now the Sydney Opera House has become a star for the environment.

The national icon has joined a select group of World Heritage buildings after being awarded a 4-star Green Star - performance rating by the Green Building Council of Australia.

And it's quite the achievement for the harbour gem, considering it's more than 40 years old.

"It puts the Sydney Opera House on the same level as the remarkable Empire State building in New York which has also achieved a similar rating," NSW Minister for the Arts, Troy Grant said.

"This sort of environmental rating is usually achieved in brand new buildings where they have access to newer building materials and planning opportunities," Mr Grant said.

The Opera House has reduced its energy consumption by 10 per cent over the past five years by retrofitting new lighting.

It also has a sea water cooling system that sources water directly from the harbour as well as green cleaning methods.

Just by installing more energy efficient lights in the concert hall, the Opera House is saving $75,000 a year.

Mr Grant hopes other businesses with ageing buildings will follow the Opera House's lead in making the investment in green technology.

He says all government buildings should pursue the 4-star rating.

"There really shouldn't be any excuses," he said.

From the 970 buildings in Australia that have achieved the 4-star performance rating, only 110 were older buildings.