The changes will also require the ESB and other electricity suppliers to indicate the environmental impact of their various fuel sources. The move has been prompted by the EU and will "enable consumers to make informed choices about suppliers based on the generation characteristics of the electricity they supply, " the European Commission said.

All energy suppliers will have to display information on customer bills regarding the contribution of each energy source to their fuel mix. The information will include a table which indicates the percentage breakdown of electricity supplied by fuel source including coal, gas, nuclear and renewables such as wind and solar.

The Commission for Energy Regulation, which is overseeing the project, decided that information on energy imported from the North-South interconnector will also have to be included. Earlier this month, ESB chief executive Padraig McManus said the company could not guarantee that energy received via the interconnector did not contain nuclear power generated in the UK.

Current legislation prevents nuclear energy being generated in Ireland. "Business outside is an entirely different issue and we look at opportunities that arise, " McManus said. The amount of energy imported from the UK is expected to increase significantly as local capacity limits are reached. Plans for a 200m interconnector between Wales and Wicklow are currently in development.

Last night, Green Party TD Ciaran Cuffe said the new billing information would force the ESB to use more environmentally friendly energy sources. "There's no reason why the ESB can't select the type of electricity source it imports from the UK. Consumers can now put pressure on the ESB to move towards renewable energy sources, " he said.