Market-wide Half Hourly Settlement Webinar

The Push to Granular Settlement

Market-wide Half-Hourly Settlement replaces profile-based estimates with actual half-hourly consumption data for all electricity supply points in Great Britain. Ofgem initiated the programme to modernise a settlement system rooted in the 1990s, where most domestic and smaller non-domestic users were settled on averaged profiles rather than real-time usage.

The shift matters urgently now because the programme has entered its active migration phase. Central systems launched in September 2025, meter migrations started in October 2025, and by mid-February 2026 over two million meters had transitioned, with the Migration & Cutover Advisory Group ending Early Life Support arrangements as systems proved stable.

Concrete deadlines loom large. Milestone 14 on 28 October 2026 requires all suppliers to have systems ready to handle Meter Point Administration Numbers under the new model; failure means they cannot sign up new customers, a direct hit to growth and market share. Full migration ends at Milestone 15 on 7 May 2027, after which Milestone 16 on 2 July 2027 cuts the settlement window from 14 months to four, sharpening financial exposure for suppliers and improving cash flow accuracy across the industry.

Impacts ripple widely. Suppliers face substantial upgrade costs for systems and data handling, while consumers stand to gain from more precise bills and new tariffs that reward off-peak usage, such as charging electric vehicles overnight or running heat pumps when wind generation peaks. Businesses, especially those with flexible loads, can optimise costs but risk higher charges if patterns remain peak-heavy without adaptation.

Non-obvious tensions include the smart meter rollout's uneven progress: although MHHS does not mandate smart meters, half-hourly data relies heavily on them or equivalent capability, creating pressure on suppliers to install or upgrade amid supply chain and consumer acceptance hurdles. Ofgem's analysis projected net consumer benefits of £1.6 billion to £4.5 billion over 2021-2045 through efficiency and flexibility gains, yet short-term transition risks include temporary billing discrepancies or supplier exits if compliance proves too costly for smaller players. The reform also exposes trade-offs between rapid decarbonisation—MHHS is deemed essential for Clean Power 2030 by unlocking consumer-led flexibility—and the practical challenges of industry-wide coordination in a fragmented market.