Market-Wide Half-Hourly Settlement (MHHS)

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MHHS is a change to the way electricity consumption is measured and billed in the UK. At present, most households and small users are billed based on non‑half‑hourly data, which relies on estimates or standard profiles rather than their actual usage. With MHHS, electricity consumption for residential customers and small non‑half‑hourly business users will, wherever possible, be 'settled' using actual half‑hourly (30-minute) usage data.

• Improve billing accuracy – ensuring consumers pay for what they actually use rather than estimated amounts.
• Support better demand forecasting – helping suppliers manage electricity more efficiently, integrate variable renewable energy, and progress toward Net-Zero goals.
• Enable smarter tariffs – allowing flexible pricing options (e.g., time-of-use or dynamic tariffs) that encourage consumers to shift usage to cheaper, off‑peak periods.
• Reduce overall system costs – lowering imbalance costs when actual usage differs from estimates and avoiding unnecessary payments for unused capacity.

MHHS implementation is happening in stages between September 2025 and July 2027:

• September 2025 – ECOES updates all topline data to include SSC. Industry systems go live, and suppliers begin updating bills.
   
• October 2025 – May 2027 – Industry migration period, during which all UK electricity sites are transferred to half-hourly settlement.
   
• May 2027 – Target deadline for migrating every electricity meter in the UK to MHHS. Each MPAN must be fully migrated with compliant meters to support the new billing process.
   
• July 2027 – The new MHHS settlement table is scheduled to be in place, enabling more accurate billing, faster reconciliations, and better insight into energy usage.

The MHHS programme is led by Ofgem, with Elexon appointed as the senior responsible owner and implementation manager.

A wide range of organisations are involved, including suppliers, network operators, data service providers, and meter operators.

Several key systems and services are being developed or upgraded:

• Load Shaping Service – creates usage profiles for non‑half‑hourly metered customers using validated data.
• Market-wide Data Service – aggregates data from all meter types for purposes such as imbalance settlement and network charges.
• Volume Allocation Service – replaces the legacy volume allocation agent.
• Other industry services – including standing data and line loss factor services.

For consumers:

• More accurate bills with fewer surprises from estimates.
• Opportunity to benefit from time-of-use or dynamic tariffs.
• Greater visibility into when electricity is used.

For businesses:

• Improved accuracy of usage data and the ability to shift demand to cheaper periods.
• Potential need to upgrade meters to smart or AMR-capable devices if not already half-hourly compliant.
• Possible adjustments to contracts, billing methods, or tariffs.

Challenges / Risks:

• The rollout is complex and has experienced delays to ensure system integration.
• If meters aren’t upgraded or half-hourly data isn’t consistently collected, estimates or profiling may still be used, reducing billing accuracy.