The development, implementation and subsequent operation of the Integrated Single Electricity Market (I-SEM) and DS3 programmes in the Irish market constituted significant new work for the Transmission System Operators (TSOs). That work included developing the design in further detail, as well as developing systems and process that administer and implement the new market arrangements. ESP Consulting was engaged with the two Irish energy Regulatory Authorities to provide ongoing assurance that the TSOs’ costs in relation to these two activities were reasonable and additional to those agreed in previous price controls. This work involved: