In a deal, Meridian Energy has won an increase in the price it gets for the electricity it supplies to the company.
But it said the price was still less than the smelter would have paid if it had relied on the rest of the market to supply a big chunk of its power.
Under previous agreements the smelter had the right to do this.
Meridian will now supply most of the smelter's 572 megawatts of power, but fuel 80 megawatts from Contact Energy into that mix.
It said the agreement committed Meridian to cover the full 572 megawatts currently used at the smelter at more competitive rates for the smelter than would have applied if it had chosen to rely on other suppliers.
The smelter meanwhile reiterated that its power was still too dear and was pinning its hopes on a cut to its transmission costs.
This matter is being debated by the Electricity Authority.
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