But not all power retailers agree on the impact.
Tiwai smelter deadline and full year results still to come for Contact.
Tim Hunter talks about Contact Energy on NBR Radio and on demand via MyNBR Radio.
NZAS is one of the most operationally efficient smelters in the world but pays one of the highest prices for power, NZAS's Gretta Stephens said.
Jenny Ruth talks about Tiwai Point on NBR Radio, and on demand on MyNBR Radio.
Contact fell 8.4% to $5.57 yesterday as the shares went ex dividend ahead of the $367 million June 23 payout.
Jenny Ruth talks about Contact Energy on NBR Radio and on demand on MyNBR Radio.