Contact Energy has announced a one-for-nine renounceable rights issue to raise around $350m to help fund new geothermal power station.

Mighty River Power is lifting its pre-tax earnings forecast by up to 7.5 per cent as it sees the benefits of $1 billion invested in new geothermal power stations.

Contact Energy is to spend $623 million building a new 159 megawatt geothermal power plant.

Two more power providers are putting up prices, with some customers facing an 8 per cent rise.