Meridian Energy is considering the sale of its 50 per cent stake in the A$1 billion Macarthur wind farm in Australia.

Meridian Energy is not a private enterprise but in negotiation with Rio Tinto it must act like one. If it can get a better power price elsewhere, Tiwai smelter must go.

Rio Tinto's attempt to renegotiate New Zealand's largest electricity contract, for its aluminium smelter at Bluff, comes as the company's chief executive warns of "difficult decisions" ahead.