Ministry of Economic Development energy and communications director Stuart Calman told the Environment Court, Government policy was to have 90% of the country's energy produced by renewable resources by 2025. He was presenting evidence for the whole of the Government submission.
The Huntly coal-fired plant would switch from base-load generation to a different role, and may be used as a peaking plant.
Mr Calman said by 2025 existing thermal stations would only be running about half of their maximum levels.
Thermal generation was at present used for base-load generation, every day of the year.
A combination of wind and hydro power would become base-load generation, he said.
Mr Calman said the way the New Zealand electricity system was set up, investment decisions were made by private companies. The commercial acumen of those companies would decide on where future generation would be sited, and how much power would be produced.
Government was not involved in this role, he said, although the Government owned power companies, as state-owned agencies.
Upland Landscape Protection Society co-ordinator Ewan Carr said with energy growth running at 2% or an extra 150MW needed every year, he wondered where all this extra generation would come from.
Mr Calman said about 900MW would come from geothermal stations, up to 1300MW would be from wind farms, and the rest would come from run-of-theriver hydro stations. New and more productive turbines could be placed in power stations.
Small-scale generation was not favoured, as it was too expensive. He considered anything producing less than 10MW as small-scale.
Ministry for the Environment climate change policy manager Philip Gurnsey said 11 Government departments were involved in the whole of the Government submission.
He said a small group of scientists did not believe climate change was produced by humans, but the Government did not believe that, and had shaped policy to reflect that.
Ministry for the Environment counsel Roanna Chan said the Government submission was focused on the national impact of the proposal, and did not take into account the impact on the local environment.
Energy consultant Bill Heaps told the court he did not break the code of the court by not outlining where he obtained information he used to compile an energy profile.
Mr Heaps said the information came from suitably qualified TrustPower employees.
TrustPower reserved its option on whether it would provide wind data to the court which it had previously said was commercially sensitive.
On Tuesday, Judge Jeff Smith questioned whether Mr Heaps was in breach of the code of court by not saying where information he used in his profiles was acquired.
