A BER is similar to the energy label for a household electrical appliance such as your fridge. The label has a scale of A-G. A-rated homes are the most energy efficient and G the least efficient.
From the 1st of January 2009 a BER certificate is compulsory for all homes sold or rented. If you are buying or renting a new house or apartment now, you are entitled to a BER - so do ask the seller/landlord or their agent for it.
All new homes (whether for sale or for let) must have a BER certificate before they are occupied as detailed under S.I. 666 under http://www.environ.ie/en/Legislation/DevelopmentandHousing/BuildingStandards/
BER assessments performed on new dwellings will also help determine compliance to Part L of the Building Regulations.
BERs will be carried out by specially trained BER assessors, registered by Sustainable Energy Ireland (SEI). A list of BER Assessors is available on the SEI website.
It is an offence for persons not registered with SEI as BER assessors to purport to carry out a BER assessment service for the purposes of the Regulations.