Mighty River Power reveals that its tariffs are ready to report a rise by April 1 this year and again from July after its obligations begin under the Emissions Trading Scheme.

Mighty River Power Chief Executive Doug Heffernan posted that prices had been frozen, however, a 3% boost on consumer bills propelled increased charges from lines companies.

At a media briefing on its interim results this afternoon, the company quoted that it would pass on costs triggering from the ETS but the market would determine how much.

"The government's position was it would expect that to flow through to consumers, but we have to wait and see how the market settles down and adapts to that implementation", Mr. Heffernan claimed.

The company's retail division, Mercury Energy grabbed 18,000 new customers for the six-month period to December 2009, but Mr. Heffernan posted that estimated value to accrete within a two-year time frame.

The degree of competition was the most aggressive it had been in 11 years of de-regulation, he added.

Most of those new customers moved from Contact Energy or Genesis Energy.