On 10 January 2017 the Ministry of Energy published in the Federal Official Gazette, an Accord that unveils the Metering for Settlement Rulebook (the Rulebook), containing the Term 16 "Metering Systems" of the Electricity Market Guidelines, and the technical requirements applicable to metering systems used to register the energy exchange between users of transmission and distribution services, as well as the carriers or distributors.

The Rulebook identifies the responsibility of the National Centre of Energy Control (CENACE), as well as the carriers and distributors to guaranty the integrity, quality and confidentiality of the metering records, and establishes that the power plants and load centers are required to acquire metering systems to comply with the applicable provisions, as well as other particularities set forth in the Rulebook.

The elements that make up the metering systems are established (meters, instrument transformers, communication systems, time synchronization systems), as well as the characteristics that such elements must comply with, including complying with Mexican Official Standards and other features. Characteristics of the metering systems differ depending on who will carry out the measurement, whether it be a carrier, distributor, power plant, load center under the isolated supply scheme, or others.

Also, carriers and distributors must (i) assess and validate the records for settlement of their metering systems, (ii) file them before CENACE, (iii) preserve them for at least ten years, and (iv) share them with the power plants and the load centers to which the transmission and/or distribution services are being provided.

Finally, the Rulebook sets forth the procedure to be followed by the carriers, distributors, power plants or load centers in the event of a failure in the metering system.

The Rulebook became effective on 11 January 2018; however, CENACE, as well as the carriers and distributors will have 180 days to make the necessary adjustments in their corresponding metering systems in order to comply with the Rulebook.