Chiller systems - the biggest energy guzzlers - in large government buildings and air-conditioning thermostats are being set a few notches up to save even more energy.

For the cooling system, it will have to meet a minimum energy efficiency rating of 4.7, higher that the 3 rating of an average bulding.

The higher rating can bring a potential power saving of between 35 to 50 per cent, said Environment Minister Yaacob Ibrahim in a written reply on Monday in Parliament.

Thermostats should also be set between 22.5 to 25.5 degree Cesius for optimum comfort - each degree up can save up to 3 per cent on power bills.

Dr Yaacob was responding to Mr Seah Kian Peng (Marine Parade GRC), who asked if the Government would consider a 'no jacket' rule for formal functions.

The dress-down policy was first introduced in Japan, where government officials opted to leave their jackets at home in a bid to save electricity on air-conditioning during sweltering summers.

Dr Yaacob said the government did not want to be 'overly prescriptive and impose rules' on all government functions, preferring to leave the dress-code to

event organisers to decide.

Instead, Dr Yaacob stressed the need to get to the root causes of higher energy usage.

"We must examine the root causes of high energy consumption and adopt cost-effective solutions to reduce excessive energy losses,' he said.

Since last year, 17 large government buildings have taken the lead in the green push, conducting audits of their energy efficiency - from lighting to air-conditioning to water use.

Of the 17, eight have introduced the recommendations, which will cut their power bills by about $2.6 million a year.

About 25 more public sector buildings, including polytechnics and ITEs, are expected to complete their energy audits by March 2010.