The last person leaving the Department of Enterprise, Trade and Employment offices switches off all electric lights, printers, photocopiers and heaters to conserve energy, the Dáil was told.
Minister Micheál Martin said a "green team" ensured all lighting in the department's eight buildings was switched off overnight, and that the OPW used energy-efficient and long-life bulbs wherever possible.
Central heating was switched on and off to achieve optimum energy-efficiency, while staff switched off all their computer equipment at the end of each working day, said Mr Martin. PC monitors were switched off at lunchtime and while meetings were in progress.
"These initiatives have had no adverse cost implications for my department, and have resulted in energy cost savings that are impossible to quantify."
Describing the Minister's remarks as "nonsense", Labour spokesman Ruairí Quinn suggested that turning off the machines was clearly a waste of time if the outcome could not be measured.
"One can look at a bill, as any sensible householder would, and see the impact of turning off all the PCs by comparing what the bill was before.
"This is the new reality for all of us, and I invite the Minister to reconsider, before we get back to real politics in September, measures by which we can quantify the impact of carbon footprint."
Mr Martin said that they might look flippantly at issues such as turning off lights, but it was recognised in research that enormous savings could be made by doing so.
