"We can't be absolutely firm at the moment with how many jobs are lost because we have to complete the consultation process. We have kicked off a process now where we support people who are in roles that are disestablished to look for opportunities for redeployment or relocation within Contact," Robinson said.
"Over the next four to six weeks the consultation process with take place and at the end of that consultation period we will know exactly which roles have been affected."
Mr Robinson said the announcement had not come as a surprise to employees at the plant.
"We have been talking about the future role of Otahuhu for the past three years because the current situation with adding renewable energy and oversupply in the market has been well known," he said.
"We have been open with employees and we had early conversations with the union and employees were told about this prior to the market announcement this morning."
Contact's chief executive, Dennis Barnes, said the closure was due to an oversupply in the market.
"Our decision to close our Otahuhu B station reflects the growth in renewable electricity generation, such as the new Te Mihi geothermal power station, which has effectively replaced Otahuhu in Contact's portfolio," Barnes said.
Two weeks ago, Genesis Energy announced the closure of its last two coal-burning electricity generators at Huntly Power Station. which will be permanently withdrawn from the market by December 2018.
The decision was hailed as another step towards having 90 per cent of New Zealand's electricity supply generated by renewables by 2025.
