Under the MHHS Programme, managed by Elexon on behalf of the industry regulator Ofgem, suppliers must balance their accounts using actual consumption data measured at 30-minute intervals, rather than relying on monthly or annual estimates. Until now, suppliers have typically taken readings once every 14 months, with final settlement taking up to 14 months to complete.  

With half-hourly settlement, Elexon says it can now complete the process within four months, allowing the market to respond to changes in demand more quickly. The reform also paves the way for more dynamic pricing models – such as time-of-use tariffs – where consumers can pay less for electricity used during off-peak periods or when renewable generation is plentiful.

The migration will run through to May 2027, with 80% of meters expected to be switched by October 2026. Elexon will operate the old and new settlement systems side by side until July 2027 to ensure a smooth transition. Once migration is complete, data will be aggregated and published through Elexon’s forthcoming Smart Data Repository, giving energy firms, researchers and policymakers more detailed insight into national consumption patterns.

Unlocking flexibility and consumer value

Half-hourly settlement (HHS) has long been used for Britain’s largest industrial and commercial consumers, but extending it market-wide is a step-change in ambition. By measuring consumption more precisely, suppliers will be able to offer tariffs that reward flexibility – for example, charging electric vehicles overnight or running appliances when renewable output is high.

The benefits are wide-ranging. Elexon says HHS will improve billing accuracy, enhance demand response, boost market efficiency and transparency, and support renewable integration by matching supply and demand in near real time.

The programme is a cornerstone of the UK government’s clean power by 2030 and net zero ambitions. By incentivising consumers to shift their energy use to periods of lower demand, the grid can operate more efficiently, reducing reliance on fossil-fuelled peaking plants and cutting carbon emissions, explains Elexon.

Data gaps threaten the promise

However, while the move to MHHS marks major progress, questions remain over whether the UK’s underlying data infrastructure is ready to deliver the promised benefits. A new report from energy data consultancy Stark warns that the UK’s metering base is ‘built on shaky ground’, with roughly one in three meters – around 11.6 million – failing to transmit accurate half-hourly data.

Stark’s analysis suggests that poor data could inflate supplier costs, drive up consumer bills and undermine confidence in the new regime. The consultancy estimates that only a third of suppliers currently meet half-hourly performance standards, covering just 12% of half-hourly consumption.

Accurate data is the foundation of the new market, the report notes, warning that without it, £4.5bn in potential savings could be lost.

The stakes for suppliers

Under Ofgem’s new performance-based model, data quality is no longer just an operational issue – it’s a financial one, says Stark. Suppliers that fail to deliver accurate half-hourly data will face penalties, while those that excel will be rewarded through a redistribution mechanism.

Stark’s modelling shows that for a large supplier, profitability could swing by as much as £42mn/y – from a £21mn loss to a £21mn gain – purely based on data performance. Mid-sized firms face potential swings of £5–8mn, and smaller ones around £1–2mn.

On a per-meter basis, the exposure could reach hundreds of pounds – ‘easily outweighing any savings from hiring a cheaper but lower-performing agent’, suggests the report.

Suppliers with automated, high-quality data systems will not only avoid penalties, but will also ‘benefit from accurate settlement, better forecasting and the ability to offer smarter, fairer tariffs’, according to the report. Those who lag behind ‘face mounting penalties, operational strain and reputational damage’.

Fixing the data deficit

The challenge lies in the 35% of Britain’s meters that either cannot, or are not configured to, send half-hourly data automatically. Some suppliers still rely on manual downloads or site visits, a practice that costs the industry around £200mn/y, notes Stark.

To fix this, the consultancy says urgent investment is needed in automated data collection, interoperable technology that works across providers, and stronger supplier accountability. Without these measures, the migration timetable could be derailed, it warns.