The number of natural gas customers switching providers reached an unprecedented high after a massive price hike from Phoenix Gas last year, it was revealed.
Around 2,500 customers changed in June last year after Phoenix increased bills by 39%. Changes had been introduced to allow domestic customers to switch supplier in the Greater Belfast and Larne areas and Firmus Energy entered the market to compete with Phoenix, the Utility Regulator said.
The watchdog has identified savings of £250 million in Northern Ireland since 2006, its annual report revealed, and overseen investment in the energy and water infrastructure of almost £5 billion.
Chief executive Shane Lynch said: "Our focus is on the twin challenges of protecting consumers and ensuring the necessary investment for the future."
He said there needed to be efficient investment to protect consumers from high prices.
"We aim to set out our stall very clearly to ensure that investment in utilities in Northern Ireland remains an attractive proposition for investors," he added.
Systems are now in place to allow unlimited switching between suppliers by electricity and gas consumers seeking the best deal. In the natural gas market, there was an unprecedented 2,508 switches in June 2011.
Within electricity, Budget Energy entered the market, which brings the number of suppliers in the domestic market to five.
Mr Lynch added: "During 2011-12, NI Water made good progress to deliver the actions in our Freeze/Thaw Recovery Plan. The company has also made steady progress in cost efficiency and service delivery."
An efficiency gap with comparable water companies in Great Britain still exists.