Market-Wide Half Hourly Settlement (MHHS) Autumn 2025 Updates

The Market‑wide Half‑Hourly Settlement (MHHS) programme is moving into its operational phase. From Autumn 2025, electricity settlement, invoicing, and data management will start to change across the UK. Most changes happen behind the scenes, but a few key updates will affect your business directly.

What is MHHS? 

MHHS is a reform that uses half-hourly meter data as the new standard for electricity settlement. Instead of relying on estimated usage for non-half-hourly (NHH) meters, suppliers will use real meter data, making billing more accurate, transparent, and flexible.

Why the Change?

• Major programme milestones and regulatory updates are driving this transition.
• September 2025 marks the start of MHHS in practice, with key code changes and new infrastructure in place.
• Businesses must comply with updated Retail Energy Code (REC) obligations by August 2025.

What's Changing in September 2025?

The Supply Number (S-Number) format on invoices and contracts will change:

• Old: Profile Type, Meter Time Switch Code (MTC), Line Loss Factor (LLF)
• New: Profile Type, Standard Settlement Configuration (SSC), DUoS Tariff ID

The SSC shows how a meter is configured for settlement. For smart/advanced meters, SSC will be ‘0000’, reflecting real-time half-hourly data instead of old classifications like “Economy 7” or “Profile Class 03.”

Impact on Your Business

• Invoice layouts and contract data may look different.
• NHH meters may need review or replacement.
• Real-time data enables flexible tariffs, better cost forecasting, and more accurate carbon tracking.
• Supports sustainability goals with clearer, actionable data.

And the best part? All this makes the business case for net zero stronger. The clearer your data, the clearer your ROI.

What You Can Do Right Now

At True Group, we help you turn complexity into confident decisions and this is one of those moments. Our True Platform fully supports the new number format, so if you're a customer with us - you're all set.

Here’s how to prepare:

• Review your metering portfolio
  Identify which sites are using NHH meters and assess what’s needed to transition to HH-ready smart or advanced metering.
• Talk to your supplier
  Ask them how they plan to handle the SSC and DUoS Tariff changes, and whether your contracts or billing terms will be affected.
• Use your data to plan ahead
  Once migrated, your sites will generate more granular data. Use True to track cost and carbon performance in real-time.
• Build business cases with confidence
  With accurate data, you can prioritise the sustainability investments that deliver real commercial returns and get buy-in faster.