The Commission for Energy Regulation has approved substantial price increases that will see the price of gas rise by over 25%.
Bord Gáis Éireann had sought an increase of 34%.
The Commission for Energy Regulation said most of the increase arises from the cost of procuring gas from the international markets over which Bord Gáis Éireann has little control.
Electricity prices are set to rise by an average of 4.1% from 1 January 2006.
The greatest impact will be for large industrial users who face a hike of 8%. Small and medium enterprises will pay 5.2% more.
However, for domestic users the price hike is 3.1%.
It is estimated that this latest price rise would increase the average two-monthly domestic electricity bill from €120 to €124.
The 25.26% increase in gas prices will take effect in three weeks time on 1 October.
