The Electricity Authority and Commerce Commission are investigating claims of price gouging by "gentailers" -- companies that both generate electricity, and sell it to consumers.
It comes as four mills propose closures or downsizing due to rising costs, and Fonterra also expressing concerns.
Meridian Energy says the industry is taking steps to maintain security of supply, but low lake levels, acute gas shortages and periods of low wind are all putting pressure on wholesale market prices.
But it says only large businesses that have chosen to be exposed to direct spot prices are affected, and most residential and business customers are on fixed price contracts.
