Environment, Heritage, and Local Government is one of the few departments to have increased electricity usage last year, according to a response to parliamentary questions.
Figures obtained by Labour Party environment spokeswoman Joanna Tuffy showed the Department of Environment's consumption increased 1.7 per cent in 2007 and was up 5 per cent since 2005.
Ms Tuffy said Minster for the Environment John Gormley was seeking external assistance to help the department cut its electricity usage.
She suggested he could also "have a chat with some of his fellow ministers to see how they have managed to bring their bills down".
"Because the Government is the biggest property owner and tenant in the State, our ministers have a key leadership role in conserving energy and reducing our carbon emissions. This is especially true for Green Party ministers," Ms Tuffy said.
The Department of Community, Rural and Gaeltacht Affairs had achieved the largest reduction - down 12.37 per cent. Other departments that achieved large reductions were Defence (9.65 per cent), Agriculture and Food (9.5 per cent) and Social, Community and Family Affairs (7.06 per cent).
Other departments achieved reduction of between 1.64 per cent and 5.63 per cent.
The Department of Arts, Sport and Tourism and the Department of Health both increased consumption by over 5 per cent.
There were no figures available for the departments of Finance and Justice.