The ESB will have to shed around 250,000 customers, on top of the 500,000 it has already lost, before it can set its own electricity prices.
The decision was made by the Commission for Energy Regulation which today mapped out how price restrictions in the electricity market will be lifted.
Customers who stick with the ESB have been warned they should not expect a significant reduction in prices after deregulation.
Currently, the Commission for Energy Regulation sets the electricity prices for the ESB and allows Bord Gáis Energy and Airtricity to under cut them to stimulate competition.
The Regulator has now said real competition can happen probably early next year, when the ESB only controls 60% of electricity consumption.
However, the Regulator warned that it was prepared to intervene in the market again, if the ESB significantly increased its customer base.
The ESB has welcomed the plan as ‘a significant milestone’ but raised a flag over the stipulation that it must change its name - saying this was challenging, complex and required careful planning to avoid confusing customers.
The Regulator said ESB customers would not see a significant drop in prices once regulation is lifted, adding electricity prices would probably remain around the current levels when reviewed in October.