NZAS chairman Brian Cooper said the smelter was one of the most efficient in the world but currently pays one of the highest power prices paid by a smelter anywhere in the world, outside of China.
Only smelters in Eastern and Southern Europe pay similar prices.
NZAS also paid one of the highest transmission charges, faced by a smelter, in the world, he said.
Costs had dramatically increased, by $25 million per annum, over the past seven years – last year the smelter paid $64 million in transmission costs.
A transmission costs system, where the grid user pays for what they actually use, would deliver a better outcome for NZAS, he said.
"No decision had been made about the future of the smelter, and we are doing everything we can to secure a long-term commercially competitive electricity price for the smelter."
Translation: "give us more money or we'll leave". To which the government's response should be "here's the door". The smelter makes a profit. There's no need to subsidise a profitable business, and no point subsidising an unprofitable one. And if it shuts down, we can deploy the resources it currently wastes - 13% of the country's total electricity supply - to more profitable uses.