The chief executive has proposed making the voluntary building energy codes mandatory as an interim response to the climate crisis.
An agreement reached at the Asia Pacific Economic Co-operation forum last month in Sydney requiring members to cut energy intensity - energy consumption per unit of gross domestic product - by 25 per cent below 2005 levels by 2030, prompted Donald Tsang Yam-kuen's move.
The law would require developers to follow the best practice in lighting and air conditioning, in all projects, including work in open spaces.
Officials said they hoped the change could cut total power consumption by 2.8 billion kilowatts in 10 years, while only adding about 4 per cent to construction costs. They said these costs could be recovered in six years from energy savings.
Drafted in 1998, the voluntary codes were rarely adopted by developers with only 45 buildings certified by the government for compliance even though buildings consume 85 per cent of Hong Kong's electricity and emit 40 per cent of the carbon.
As a pilot project, the new government headquarters at Tamar will submit to a carbon audit when it comes into operation, and an emission reduction campaign will be launched.