MHHS

Historically, only large business meters recorded exactly when electricity was used in 30-minute intervals. Everyone else had their usage estimated from typical patterns for their customer type. MHHS changes this: in time, all meters (including domestic smart meters) settle on actual half-hourly data.

Timeline:

• 22 September 2025 - Go-live. Industry code changes take effect and the supply number format moves to 22 digits.
• 22 October 2025 - First meter migrations begin.
• 28 October 2026 - Target for all suppliers to be qualified to operate under MHHS.
• 7 May 2027 - Target for all meters migrated to half-hourly settlement.

What's changing:

• Settlement uses actual half-hourly consumption instead of estimated profiles
• The profile-estimation system (D0018 coefficients) is replaced by the Load Shaping Service
• Migrated meters move to Profile Class 00
• The supply number gains a digit as the 3-digit MTC becomes the 4-digit SSC
• The LLFC field on the supply number becomes the DUoS Tariff ID (charging), with a separate LLF ID used for losses in settlement

What's NOT changing:

• The Distributor ID still identifies your DNO region
• DUoS tariff categories, time bands and rate structures stay the same
• At go-live the DUoS Tariff ID is identical to the existing LLFC, so charge lookups are unaffected

The practical effect for organisations is that settlement, and increasingly the time-of-use signals in your charges, reflect when electricity is actually used, not just how much.