BHP Billiton expects South African power utility Eskom to honour deals that are letting the mining giant buy electricity for its smelters at just over half the cost of production, the company said on Wednesday. Eskom, which needs to generate cash to build new power stations to meet rising demand in Africa’s biggest economy, has been trying to renegotiate the long-term preferential deals since 2009. It has now asked the energy regulator to review the contracts, which are linked to the price of aluminium and the rand/dollar exchange rate and which contributed in large part to Eskom’s annual loss of 9.7 billion rand ($1.05 billion) in 2009.