Mighty River Power was one of the Crown-owned companies partially sold down by the Government, a move bitterly opposed by Labour and Green MPs, in particular.
The Opposition parties proposed a central energy buying authority, claiming power prices would fall.
Share prices of the energy companies fell during the election campaign but rose sharply after the election when it became clear National would again lead the Government.
Mr Timms said there had been energy price increases but they had not been driven by the generating-retailers (gentailers) such as Mighty River.
Companies such as Transpower, and local authority-controlled lines companies, had pushed up prices behind the scene to raise revenue to maintain the lines network around the country.
There would be higher demand for energy as the economy grew and lines companies would need to spend more on infrastructure as the lines networks would not last forever.
The older the lines, the higher the drop-off in electricity between the generation assets and the end user, he said.
''Mighty River is holding its costs down, absorbing every increase from the lines companies. But you may find there will be an increase of energy prices, at some stage.
''If what the Greens said was correct, you would get shareholders jumping up and down because prices were going up without a significant increase in dividend. Mighty River is holding costs and still providing a sufficient rate of return.''
Mighty River Power customer general manager James Munro said holding headline energy prices again reflected the company's focus on offering good service and value in a highly competitive market.
''For the third year in a row, we have decided not to increase our headline energy prices.''
There would be changes in customer pricing from April 1 due to costs over which the company had no control, he said.
About half of the price to customers was for ''delivery'' of electricity.
Most of those costs were regulated and included charges from the grid, local lines companies, metering and the Electricity Authority levy.
Those increases or decreases would be passed through to customers, as usual, he said.
