Half-hourly Settlement One Year On: What UK Businesses Need to Know

Half-Hourly Settlement, One Year On: A Practical Retrospective

A year after Ofgem’s Market-wide Half-Hourly Settlement (MHHS) was fully implemented, the UK energy market has undergone a fundamental shift in how consumption is measured, priced, and managed. For businesses with half-hourly (HH) meters, the change is no longer theoretical—it’s operational. The new settlement regime, which replaced the legacy half-hourly data (HHD) system with a market-wide standard, has eliminated discrepancies between actual usage and billed consumption, improved transparency, and unlocked new opportunities for cost optimisation. However, a significant number of businesses remain on contracts that treat them as if they are still on non-HH tariffs, missing out on savings and exposure to avoidable costs.

The core thesis is simple: MHHS has transformed energy management from a passive billing exercise into an active, data-driven function. Businesses that have adapted—by leveraging their half-hourly data, engaging in flexibility markets, or switching to dynamic tariffs—have already seen measurable savings. Those that haven’t are effectively paying a premium for outdated assumptions.

What Has Changed Since MHHS Launch?

MHHS, introduced in January 2023 and fully operational by January 2024, mandates that all electricity suppliers settle with the market based on actual half-hourly consumption data. This means that billing is now aligned with real-time usage, eliminating the previous lag and estimation errors that affected both suppliers and consumers. For businesses, this translates into:

• Accurate billing: No more estimated bills. Consumption is settled on a half-hourly basis, reducing disputes and improving forecast accuracy.
• Visibility into load patterns: Real-time data reveals peaks, off-peak periods, and inefficiencies that were previously hidden.
• Access to new tariff structures: Dynamic pricing, time-of-use (ToU) tariffs, and flexibility services are now viable options for HH-metered sites.

Ofgem’s move was driven by the need to support the integration of renewables and demand-side response. With the UK’s grid becoming more variable, accurate, granular data is essential for balancing supply and demand. The new system also supports the upcoming capacity market reforms and the evolution of the Balancing and Settlement Code (BSC).

Where Are the Savings Now?

The most immediate opportunity for savings lies in tariff switching. Traditional fixed-rate contracts are no longer appropriate for HH-metered sites. Instead, businesses should consider:

• Time-of-use tariffs: These charge different rates based on the time of day. For example, a site with high consumption during off-peak hours (e.g., overnight charging or manufacturing) can reduce costs by shifting load.

• Dynamic pricing contracts: These adjust rates in real time based on grid conditions. TUS has seen clients achieve average savings of 27% by switching to such tariffs, using the Yolk platform to monitor and respond to price signals.

• Flexibility participation: Sites with controllable loads (e.g., battery storage, EV charging, or industrial processes) can earn income by offering grid services. With MHHS, the data required to participate in the Capacity Market, the Balancing Mechanism, or the Demand Side Response (DSR) markets is now available and verifiable.

TUS manages over 150 GWh of demand under flex management, and in the last 12 months, we’ve consistently beaten supplier projections by 20%. This is not a one-off—it’s a result of real-time data utilisation and strategic load shifting.

The Hidden Risk: Contracts That Still Treat You as Non-HH

Despite the rollout, many businesses are still operating under contracts that assume they are not half-hourly. These contracts typically:

• Use annual fixed rates with no granular pricing.
• Ignore peak demand charges (which are now calculated on a half-hourly basis).
• Fail to account for the true cost of high consumption during constrained periods.

This mismatch creates a risk of significant overpayment. For example, a site with a peak demand of 1.2 MW during a half-hourly window may be charged at a rate that reflects the highest 12 months of demand, even if it’s only a one-off event. Under MHHS, such peaks are now precisely captured and priced, making it essential to have a contract that reflects this reality.

Furthermore, suppliers are now able to price risk more accurately. If your contract doesn’t reflect your actual half-hourly profile, you are likely being charged a premium to cover the uncertainty. This is especially true for sites with variable or high-impact loads.

What Should You Do Now?

The first step is to audit your current contract. Ask your supplier:

• Is my tariff based on half-hourly data?
• Are peak demand charges calculated on a half-hourly basis?
• Does my contract allow for load shifting or flexibility participation?

If the answer to any of these is no—or if your contract is silent on half-hourly settlement—then you are likely missing out on savings.

Next, assess your data. You should be able to access your half-hourly consumption data via your supplier or through a third-party portal like Yolk, which TUS uses to deliver free, real-time visibility to clients. This data is the foundation of any energy optimisation strategy.

Finally, engage with a specialist. TUS works with over 30 suppliers and uses a data-driven approach to identify savings opportunities. For example, voltage optimisation—deployed at sites with 5–15% savings potential—can deliver a 2–3 year payback, especially when paired with half-hourly data to track performance.

Bottom Line

One year after MHHS, the UK energy market is more transparent, more dynamic, and more responsive to real-time conditions. But this transformation only benefits those who act. Businesses still on outdated contracts are effectively subsidising inefficiency. The opportunity to reduce costs, improve grid resilience, and unlock new revenue streams through flexibility is now available. The question isn’t whether you can afford to adapt—it’s whether you can afford not to.

The transition to MHHS is not a one-time event. It’s the beginning of a new era in energy management. The time to act is now.