23 percent of residential properties nationally have an energy rating of E or lower.
Figures from the Central Statistics Office show the highest proportion of homes with a G rating is in Leitrim and Roscommon.
Dublin County, Kildare and Meath have the highest proportion of homes with an A rating, with around one in six house getting the most energy efficient mark.
While around one in eight homes in Roscommon, Leitrim, Offaly and Tipperary, as well as one in 10 in Mayo have the lowest possible rating.
14% of homes in Longford have a rating of D1.
56 percent of homes nationally have an energy rating of at least a C.
The CSO figures also show that 4 in every 10 houses across the country are heated using gas, while 37 percent use heating oil.
The average age of a house nationwide is 32 years, while the youngest homes are in Galway city, aged 25 on average, while the oldest are in Cork City at 45.
