Marketwide Half Hourly Settlement is due to begin rolling out from September 2025, according to a Which? policy research report published in November 20241. The report states that the rollout will mean suppliers face a greater incentive to offer tariffs to consumers which more accurately reflect the real-time costs of supply1.
The report, which examined how consumers find, choose and use demand-side response (DSR) tariffs, sets the settlement change in the context of slow take-up of flexible tariffs. Which? Sustainability Tracker 2024 found 8% of adults across the UK said they had a static time-of-use tariff, 5% said they had a dynamic time-of-use tariff and 3% a type of use tariff1. A static time-of-use tariff offers two or more rates for electricity at fixed times of the day, while a dynamic time-of-use tariff offers a different price per unit depending on the time of day, with times and rates that can change from day to day1.
The report also notes that an estimated 3 million consumers remain on legacy time-of-use tariffs such as Economy 7 and Economy 10, originally designed for households with electric storage heaters, with concerns around fair treatment raised in recent years1. On the potential scale of flexible consumption, it states that if realised, the benefits could save consumers billions of pounds per year by 2030, and potentially tens of billions by 20401.
The research drew on 25 in-depth interviews with consumers currently on or considering DSR tariffs and an online survey of 1,136 Which? members in August 2024, in which 21% of respondents reported being on a DSR tariff1. Among those members on a DSR tariff, 31% identified their energy supplier's guidance as the primary reason for their initial awareness of the tariff, and 47% reported visiting energy providers' websites as their most common action1. The report found 44% reported spending under an hour on their journey, while 35% reported spending multiple hours researching, often over multiple sessions1.
"However, progress is slow and needs to speed up, particularly with Marketwide Half Hourly Settlement due to begin rolling out from September 2025."
The report adds that in a June 2024 Sustainability Tracker Survey, only half of consumers with an electric vehicle said they were on a DSR tariff (51%), and that the DESNZ Public Attitudes Tracker found two-thirds of consumers know at most "a little" about time-of-use tariffs1. It also records that 96% of cars on the road run on fossil fuels, with around 3.75% fully electric1.
Why it matters for households
Settlement is the back-office process that determines what suppliers pay for the electricity their customers use. Moving the market to half-hourly settlement means consumption is accounted for in half-hour periods rather than through profiled estimates, so the cost of supplying power at a particular time is attributed more directly to the households using it. The report's expectation is that this gives suppliers a stronger commercial reason to design tariffs around when electricity is cheap, which is the mechanism by which households with a smart meter could be offered more time-of-use and dynamic products.
For a household, the practical effect depends on whether it can move consumption, such as EV charging, heating or appliances, away from peak periods. The report notes that consumers able to shift more of their consumption to off-peak or high-generation times can benefit directly by substantially reducing their bills, and that higher take-up of flexible consumption can reduce costs for all consumers by lowering overall peak demand1. It also identifies frictions: consumers often miss out on DSR tariffs, find research time consuming and stressful, and cannot always tell whether they are benefiting financially1. Comparison services rarely cover these tariffs in full, it adds1.
What happens next
The report says Which? will continue work identifying the policy changes required to address the challenges it sets out, with recommendations to be detailed in a forthcoming policy report1. It invites engagement from interested stakeholders as it shapes those proposals1. No further dates for the settlement rollout beyond September 2025 are given in the report1.
Sources1 cited
- DSR Report draft v2, media.product.which.co.uk