Rio Tinto's Aluminium Reset Could Reshape Its Entire Earnings Profile

Rio Tinto has always been an iron ore story. The Pilbara operations generate the bulk of group cash flow, and the market prices the stock accordingly — tracking iron ore futures with almost mechanical correlation. In 2021, when iron ore hit $220 per tonne, Rio earned $21.1 billion in net income. As prices normalised, net income fell to $10.0 billion in 2025.

But here is what the iron ore fixation misses: Rio's aluminium segment has been quietly restructuring for three years. Energy costs — the single largest input for aluminium smelting — have been the margin killer. The Boyne Island deal addresses that directly, replacing volatile fossil fuel contracts with long-term renewables arrangements backed by state government commitments.

We have covered the aluminium smelting cost curve across three complete cycles. When energy costs drop by 15-20% on a structural basis, the margin impact flows straight to the bottom line. There is no demand sensitivity in the equation — it is pure cost reduction.

Global aluminium supply is tighter than the headline numbers suggest. Chinese smelter capacity — which accounts for roughly 60% of global output — is bumping against the government's 45 million tonne cap. Indonesian export restrictions on bauxite are constraining feedstock. And now Emirates is flagging a year-long production recovery timeline.

Rio operates the world's largest integrated aluminium business outside China. When supply tightens and your cost base is falling simultaneously, the earnings leverage is enormous. A $100 per tonne increase in aluminium prices, combined with a 15% energy cost reduction, could add $1.5-2.0 billion in annual EBITDA to the aluminium segment alone.

That is a 10-15% uplift to group earnings from a segment the market largely ignores.

Barclays recently flagged limited steel impact from geopolitical tensions but highlighted China's dominance as a structural risk for metals supply chains. Rio's positioning outside the Chinese system — with Australian, Canadian, and Icelandic smelter operations — makes it a natural beneficiary of any supply chain diversification trend.

Against BHP ($186.7 billion market cap, 18.2x PE) and Vale ($69.8 billion, 29.4x PE), Rio trades at a clear discount on forward earnings at 11.8x. The dividend yield of 4.24% is the highest among the three majors. Part of that discount reflects the market's scepticism about aluminium. If the Boyne Island economics work — and the government backing suggests they will — that discount narrows.

The copper story adds another layer. Rio's Oyu Tolgoi mine in Mongolia is ramping underground production, and the Resolution Copper project in Arizona remains a long-dated option on copper prices. But aluminium is the nearer-term catalyst, and it is the one the market is sleeping on.