As Ofgem’s Market-wide Half Hourly Settlement (MHHS) migration begins, new analysis from energy data specialist Stark warns that poor data quality across Britain’s metering system could derail the £4.5 billion in benefits the regulator expects from the reform.
The report, Bad Data, Broken Energy System, found that around 11.6 million electricity meters, roughly a third, are not sending accurate Half-Hourly data. Many are technically capable but are not configured or maintained correctly. This means the industry still relies on estimates and manual reads, which inflate costs and undermine trust.
Only a third of suppliers currently meet Half-Hourly performance standards, accounting for just 12% of consumption. In the Non-Half-Hourly market, fewer than one in five suppliers meet the benchmark.
Stark’s modelling shows that under the new performance-linked charging regime, supplier exposure can swing by up to ±£21 million a year depending on data accuracy. Poor performers will pay penalties based on estimated energy volumes, while high-performing suppliers will receive payouts. The industry as a whole nets to zero, but individual outcomes will vary sharply.
Despite this, the first phase of the programme started on Wednesday 22 October, and will eventually see suppliers settle accounts using real consumption data within seven working days. Early waves must complete by July 2026, with full market cut-over by July 2027.
Alex Warren, Chief Executive of Stark, said, “Manual readings alone cost the market more than £200 million annually, and only five of nineteen agents have so far qualified for the new Advanced Data Service (ADS) role that underpins the reform.
“Half Hourly Settlement is essential for a fair, flexible energy market, but the system can only work if the data behind it is reliable. The technology exists, but what’s missing is consistent performance and accountability.
“Without that, Ofgem’s biggest reform risks failing before it has even begun.”
The full report, Bad Data, Broken Energy System, is available here.
