About £2 million of electricity is stolen each year, according to the ESB, which warned that electricity theft endangers lives.
The company said the theft was hazardous to those interfering with supply and a threat to innocent people living or working in buildings affected and members of the emergency services.
Theft methods vary from tampering with ESB mains to interfering with meters. This can mean that when the power supply to a building is switched off for electrical maintenance or in an emergency, the supply remains "live".