Preparing for MHHS – Modification P432

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MHHS is the biggest change programme to hit the energy industry since privatization – revolutionising how we generate, consume and manage the energy that we use.  The multi-year transformation project has a series of milestones along the way that aims to bring all meter types in line, ready for the shift to settlement on the half hourly period.

Modification P432 is one of those key milestones, and with its implementation in mid April, suppliers are now mandated to start to move any Non-Half Hourly (NHH) Current Transformer (CT) Meters to Half Hourly (HH) so that HH consumption data can be used for settlement.

What is it?

This Modification is designed to align the Balancing and Settlement Code (BSC) definition of an Advanced Meter with that in the Standard License Conditions (SLC) and to set explicit Half Hourly (HH) Settlement obligations for Current Transformer (CT) Advanced Meters ahead of the migration to Market-wide Half-Hourly Settlement (MHHS). 

Existing CT Advanced Meters settling Non-Half Hourly (NHH) are required to move, using the Change of Measurement Class (CoMC) process, to settle HH by MHHS Milestone M14 (in the MHHS Transition Timetable) – currently March 2026 based on the latest MHHS re-plan documents.

If suppliers do not start to move now there is a risk that there will be insufficient time for Customers, Suppliers and their Agents to address issues that may arise through the CoMC process – especially against the backdrop of the wider MHHS migration activities that will be needed for Smart Meters.

What’s a CT Meter?

A CT Meter is used on electricity loads of over 100 amps – allowing large loads to be measured by reducing the level of current passing through the meter to a manageable level. An example CT Ratio is 200/5 – that means that for every 200 amps of current received, only 5 amps are passed through the meter.

If I have a NHH CT Meter what do I have to do?

In order to move from NHH to HH, CT meters must undergo a process called ‘Change of Measurement Class’ (CoMC).

What is the Change of Measurement Class Process?

All energy meters are currently categorised by seven different classes ranked A-G – depending on how they are currently measured. The CoMC process is an existing process that is used for any meter moving between measurement classes. P432 will use the CoMC process to migrate AMR CT meters.

For most meters – the process can be carried out remotely via communication with the meter. However, some older CT meters might not have the right comms infrastructure in place, for example, inoperable comms which are old, faulty or non-existent, meaning the meter is unable to be read remotely.  In these cases, a physical visit will have to be scheduled, and in the case of older or faulty meters, a meter replacement may have to be organised.

As part of the CoMC process, suppliers have to de-appoint their Metering Agent in the Non Half Hourly market and then reappoint them to the meter in the Half Hourly market – this also need to be planned to ensure there is enough time and resource to complete the change.

That’s why it’s critical that supplier or end users work closely with their Metering Agents to ensure that the right plans are put in place as early as possible – to meet the March 2026 deadline.

IMServ have been supporting customers in the transition to HH settlement since 2017- as we are market leaders for the ongoing delivery of Modification P272. This earlier HH Modification was one of the largest market changes the industry had seen prior to the MHHS programme, which saw the migration of PC5-8 meters move to HH settlement.

Whilst the timescale for P432 was formalized earlier this year, IMServ have been working with our customers in preparation for P432 and MHHS for years. Our work has included regular reporting on CT meter performance and highlighting the remedial actions required to support the change of Measurement Class process, as well as creating bespoke solutions for more complex meter set ups.

We’re ideally placed to support our customers through the changes needed to become compliant under P432. We have regional coverage, with a fully trained field force to deal with niche and bespoke solutions to ensure industry compliance, customer satisfaction and an enriched data set.

You can find out more about the work we did on P272 with our customer Opus Energy here

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Preparing for MHHS – Modification P432

MHHS is the biggest change programme to hit the energy industry since privatization – revolutionising how we generate, consume and manage the energy that we