Over 80,000 customers have made the switch from the ESB to Bord Gáis, a Joint Oireachtas Committee has heard.
Bord Gáis entered the electricity supply market four weeks ago.
The Secretary General at the Department of Communications, Energy & Natural Resources, Sarah White, said there is still a long way to go before ESB's dominance in the market is reduced.
ESB currently has a 95% share of the electricity supply market.
Ms White was speaking at the Joint Oireachtas Committee on European Affairs which today discussed an EU Green Paper: Towards a Secure, Sustainable and Competitive European Energy Network.
Read the EU Green Paper
The Secretary General also said the Government would spend €7m on ocean energy this year as part of a €26m ocean energy programme.