 An area in which the island operates as a single market is electricity . For much of their existence electricity networks in the Republic of Ireland and Northern Ireland were entirely separate . Both networks were designed and constructed independently post partition . However , as a result of changes over recent years they are now connected with three <unk> and also connected through Great Britain to mainland Europe . The situation in Northern Ireland is complicated by the issue of private companies not supplying Northern Ireland Electricity ( <unk> ) with enough power . In the Republic of Ireland , the <unk> has failed to <unk> its power stations and the availability of power plants has recently averaged only 66 % , one of the worst such rates in Western Europe . <unk> is building a <unk> transmission line between Ireland and Great Britain with a capacity of 500 MW , about 10 % of Ireland 's peak demand . 
