Traditional approaches to retail electricity market monitoring rely on assumptions of the representative customer and the price it pays. Such approaches fail to account for consumer diversity or diversity in the range of competing offers. We develop an approach that prices, at monthly resolution, a large sample of customers’ bills on all competing offers available to each customer. This establishes a dataset of around 4 million possible bills each month. We segment these data to provide information on the trends in bills, the effect of discounts, to contrast retailers’ pricing strategies and of the savings available to customers if they switch to cheaper offers. Further segmentations could be considered to analyse additional aspects. Establishing a longitudinal sample of customer bills would substantially enhance the approach developed here.