More wind farms will be built in both the North and South Islands, as part of Contact Energy's massive investment in renewable power generation.

The company has announced a $2 billion plan to develop its existing geothermal stations, and build new ones. Up to four wind farms will also be constructed.

Spokesman Jonathan Hill says the company has been looking at renewable energy for some time, and needs to bring on new generation facilities by the year 2012.

He says the company believes up to 700 megawatts of power can be generated at two sites it is already negotiating for. Mr Hill says two geothermal power stations will be built in the Taupo area. He says geothermal energy is the only form of renewable energy that doesn't depend on the weather and will make a significant contribution to a secure electricity supply.

Contact Energy has told its shareholders not to expect a capital return on their investment because of its plans to go green.