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Half-hourly meter

What is a half-hourly (HH) meter?

Two business sites can have the same annual electricity consumption and end up with completely different bills. The reason is usually that one is on a half-hourly meter and the other is not. A half-hourly meter, almost always shortened to HH meter, is a UK electricity meter that records consumption in 30-minute intervals across the day and pushes the data automatically to industry systems. Every site has 48 settlement periods each day. The meter measures consumption in each one, the data flows through a Data Collector and Data Aggregator to the supplier, and the bill is built from actual half-hourly numbers rather than monthly meter reads paired with seasonal estimates. HH metering is mandatory on UK electricity supplies above 100 kW maximum demand (roughly 100,000 kWh per year). Increasingly it is used voluntarily on smaller sites where time-of-use tariffs or pass-through contracts need the granular data.

HH meters typically appear at the larger end of business electricity consumption, often as part of a wider meter installation or upgrade project.

For UK business customers, moving to a half-hourly meter changes everything about how the bill is calculated and how procurement works. Bigger sites have been on HH for decades. Mid-market sites are increasingly moving onto HH as Market-wide Half-Hourly Settlement (MHHS) rolls out across the country. The change reshapes which charges apply, who you contract with for the metering itself, and how much detail you can interrogate in the bill.

What a half-hourly meter actually does

An HH meter records electricity consumption in 30-minute intervals throughout the day.

• 48 settlement periods per day, each 30 minutes long.
• The meter stores a kWh consumption value for every period.
• The data is collected automatically (no meter reader visits) via a modem, SIM card, or wired data link.
• The supplier bills from actual HH data rather than monthly meter readings.

The combination of granular data and automatic collection makes HH metering fundamentally different to non-half-hourly (NHH) metering. NHH bills consumption over weeks or months using estimated reads in between. HH bills the actual consumption for each individual half-hour.

When a site must be on HH

HH metering is mandatory on UK electricity supplies that exceed either of the following triggers.

• Maximum demand above 100 kW.
• Annual consumption above approximately 100,000 kWh (the rule of thumb associated with 100 kW peak).

Sites at or above these thresholds are required by industry rules to install HH metering and operate under HH settlement. Below the threshold, HH is voluntary. A growing number of mid-market sites move to HH voluntarily to access time-of-use tariffs, pass-through contracts, or flexibility revenue opportunities.

The three industry roles around HH

Three separate parties operate around an HH meter, distinct from the energy supplier.

• Meter Operator (MOP). Installs, maintains, and replaces the meter and the data communications equipment. See the MOP glossary entry.
• Data Collector (DC). Reads the HH data from the meter and validates it.
• Data Aggregator (DA). Aggregates the validated data and passes it to the supplier for billing.

For UK businesses on HH supplies, the MOP and DC/DA contracts can be supplier-bundled or held directly with the customer. Larger portfolios usually contract directly for better pricing and continuity across supplier switches.

How HH data flows

1. The HH meter records 48 consumption values each day.
2. The data is collected automatically by the Data Collector via the communications equipment maintained by the MOP.
3. The Data Collector validates the data and corrects any obvious anomalies.
4. The Data Aggregator combines validated HH data across all of a supplier’s sites.
5. The supplier uses the aggregated data to settle wholesale costs and to bill the customer.
6. The customer can usually access the raw HH data via the supplier portal, normally with a 1-2 day lag.

How HH metering changes the bill

Several bill components only apply on HH sites.

• Capacity charges. Half-hourly meters drive the capacity charge based on agreed supply capacity (ASC). See kVA.
• DUoS charges. Distribution Use of System charges are applied with red/amber/green bands that vary by half-hour.
• TNUoS charges. Transmission Network Use of System charges including triad band exposure where applicable.
• BSUoS charges. Balancing Services Use of System charges.
• Wholesale unit rate. Can be billed as a flat per kWh rate, or passed through at the actual half-hourly wholesale price, depending on contract structure.

The result is a bill with materially more line items than an NHH bill, and substantially more opportunity for both cost reduction (through targeted load management) and bill errors (through complex charge calculations).

Cost example: HH vs NHH

To show how the maths plays out, here is a simple illustrative example for a site that consumes 200,000 kWh per year. Assume a fixed all-in rate of 28 p/kWh on the NHH equivalent, and an HH bundle that prices the energy at 24 p/kWh but adds capacity, DUoS, TNUoS and BSUoS as separate lines.

Example only. Real HH vs NHH economics depend on the site’s consumption shape, ASC sizing, DUoS band exposure, and contract structure. The above figures are illustrative.

On this example, total cost is close to neutral. The HH structure becomes cheaper when load management can lower peak DUoS or capacity costs, or when wholesale pass-through delivers a lower energy rate than the fixed all-in NHH price. The HH structure becomes more expensive when load is heavily concentrated in peak periods or when capacity is oversized.

Pros and cons of HH metering

Managing HH portfolios

For UK businesses with multiple HH-metered sites, the operational pattern is fairly consistent.

• One MOP contract covering all sites, with service-level commitments on fault response and data availability.
• One DC/DA arrangement covering all sites, often bundled with the MOP supplier.
• A bill validation routine that audits HH bills against contract terms, with a tolerance threshold for human review.
• An energy data system (in-house or via a third party) that pulls HH data from the supplier portal daily and produces consumption analysis for operations.
• An annual capacity review across sites to align ASC to actual peak demand.

The combination produces useful insight (which sites are heavy on red-band DUoS, which sites are close to capacity excess, which sites have an unused ASC margin) and reliable bill accuracy.

Market-wide Half-Hourly Settlement (MHHS)

MHHS is the UK industry programme moving all sites to half-hourly settlement by 2026. The programme is rolling out in tranches.

• Larger non-domestic supplies were always HH.
• Smaller non-domestic supplies (the bulk of UK businesses) are migrating during the MHHS rollout.
• Domestic supplies follow over the next 2-3 years.

The effect on bills will vary by tariff. For most customers the change is invisible operationally, though the underlying settlement and supplier-side cost recovery becomes more sensitive to when energy is used.

Moving a site onto HH

Voluntary move from NHH to HH involves:

1. Confirming the meter type. Some smart meters can operate in HH mode without replacement.
2. Engaging a MOP and DC/DA (directly or via the supplier).
3. Submitting a change of metering arrangement through industry data systems.
4. Establishing a new HH-priced supply contract or moving onto an HH-eligible variant of the existing contract.
5. Going live on the agreed effective date.

The process typically takes 6 to 12 weeks. Costs include the new MOP/DC/DA arrangements, any meter replacement, and the time to evaluate and procure HH-priced contracts.

Related entries. Meter Operator (MOP), kVA, MPAN, smart meter (SMETS2), bill validation, profile class.

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