Esso and ESB entered into a long-term contract for the sale and purchase of natural gas for a period of 15 years beginning October 1, 1999. The contract allowed for adjustments to the price to be made only when the ‘energy’ portion of the price – as opposed to the ‘transportation’ portion – was 85% or less than the market price for gas supplied in similar quantities and in similar circumstances, at the time the review request was made.

On November 1, 2002, Esso claimed the energy portion of