Over the past century, Ireland's electricity sector has undergone a significant transformation. This paper documents the nation's struggle to build an electricity system, to improve security of electricity supply through portfolio diversification and to promote indigenous energy sources. This was a challenge for an (electrically) isolated island with little natural resources. The paper also identifies the ineffective policy decisions that left Ireland exposed to the 1970s energy crises. The crises did, however, provide a clear impetus for focusing Irish energy policy going forward. The successful deployment and integration of large-scale wind power was due to strong national and supranational policy decisions. In 2015, Ireland had the third highest wind energy share of national electricity demand (22.8%) of all IEA Wind Member Countries. The paper also traces Ireland's transition through market reform, regional fragmentation, and looks onwards to the EU internal market for electricity. In essence, this paper provides a holistic view of the implications of various policy decisions on the electricity sector along with the stresses of external factors on the electricity market and should be useful for policy makers elsewhere faced with similar decisions.