Before we can assess how well renewable supply matches customer demand, we need to understand what that demand actually looks like.
For the first time, newly available public data lets us track exactly when Britain's energy suppliers are serving power to their customers. The patterns reveal as much about the suppliers themselves as they do about the renewable matching challenge.
Where demand data comes from
Elexon publishes half-hourly metered volumes for every Balancing Mechanism Unit on the grid. This includes the Supplier BMUs that track each supplier's customer demand.
We aggregate these settlement volumes to determine the total demand for each supplier, with a calibration to account for embedded generation (see our methodology for details).
Daily and seasonal patterns
Demand isn't constant. It varies by hour, by day, by season—and by the type of customer a supplier serves.
Take a winter weekday evening. Demand surges as people return home, switch on lights and heating, start cooking. A supplier serving residential customers sees sharp peaks around 6pm. But a supplier focused on industrial contracts might see steadier demand throughout the day, with different peak hours driven by shift patterns and manufacturing processes.
Seasonal variation matters too. A domestic supplier's winter demand can be almost twice that of summer, driven by heating demand and shorter daylight hours.
Then there's the business mix. Many suppliers predominantly or only serve business customers, many with base-load requirements. For example, Drax's demand profile is remarkably stable—gentle daily variation, modest seasonal swings. Compare that to Octopus who are serving millions of homes. Their profiles show pronounced daily peaks and dramatic seasonal differences.
Market dynamics
Demand changes for another reason: customer movement. Suppliers win and lose customers constantly. When Bulb collapsed in 2021, its 1.5 million customers were allocated to Octopus, whose demand jumped accordingly. When smaller suppliers exit the market, their load gets redistributed to whoever picks up the customers.
The data shows this clearly. Some suppliers grew demand by 15-20% year-on-year in 2024. Others shrank. In a competitive retail market where margins are tight, even modest customer loss shows up immediately in half-hourly settlement data.
Business-to-business suppliers face different dynamics. Fewer customers, larger contracts, longer commitment periods. A single large industrial customer can represent as much load as several thousand homes. When B2B suppliers win or lose a major contract, demand can shift by tens of megawatts overnight. If you select Bryt Energy and Brook Green in the chart above, you'll see what appears to be a direct transfer of demand between them.
Why half-hourly demand matters for matching
Accurate renewable matching depends on knowing exactly when customers use power. Annual matching—the current standard—obscures this entirely. Suppliers are perfectly allowed to accumulate cheap summer solar certificates and claim "100% renewable" while serving fossil power on windless January evenings. The demand profile makes that disconnect obvious.
When we track demand at half-hourly resolution, we can compare it directly with when renewables are actually generated, and what customers actually receive.
The charts above show total demand for major UK suppliers through 2024/25. Watch how profiles diverge—some steady, some volatile, all responding to the same physical need for supply and demand to be balanced at all times.
The Matched Clean Power Index
In October, we'll publish the Matched Clean Power Index—the first independent ranking of UK energy suppliers by the clean power they deliver to their customers. Using the demand data shown here, combined with half-hourly renewable generation profiles, we can calculate matching scores for every major supplier.
Suppliers or other interested parties who'd like to preview the index ahead of publication can contact us at contact@matched.energy.