Energy use in residential properties is falling despite a significant increase in the number of households, according to the Sustainable Energy Authority of Ireland (SEAI).

In a report released yesterday, the authority noted that residential energy usage fell 8 per cent from 2006 to 2011. During the same five-year period energy usage per dwelling fell 18 per cent.

Kevin O’Rourke, head of low carbon technologies at the authority, said about half of the drop could be attributed to improvements in the quality of residential buildings.

This includes better insulation, more efficient heating systems and the retrofitting of some 200,000 houses with attic insulation, draught proofing, energy efficient lighting and cavity wall insulation.

“A house being built to today’s regulations . . . will have less than one-fifth of the energy use and CO2 emissions of its equivalent built in the 1970s,” he said.

These factors have contributed to an annual energy cost saving of €56 million and a shift from lower building energy rating grades for such properties to the higher grades.

Mr O’Rourke said the figures provided evidence that building regulations and retrofit programmes are working.

However, he said the latter need to be extended “further and deeper” in order to meet national targets.

The year 2006 had marked a “turning point” in energy consumption, he said, noting that during the five years that followed the pace of energy efficiency improvements more than trebled.

Mr O’Rourke added that changes in “behaviour and choice” were also leading to a reduction in energy use, although the reasons behind these changes are unclear.

Average household expenditure on energy fell by 2.8 per cent during the study period.

Some 1.65 million households spent about €3 billion on energy in 2011, or an average of just over €1,800 per home.