Half-hourly meters: a guide for business electricity users

Half-hourly metering used to be something only factories, hospitals and big offices had to think about. That is changing. Every electricity meter in Great Britain is being moved onto half-hourly settlement by 2027, and larger sites already pay for their electricity in a way that depends on when, not just how much, they use.

This guide explains what a half-hourly (HH) meter is, when it is mandatory, what the market-wide switch means, and how HH bills are put together.

What is a half-hourly meter?

A half-hourly (HH) meter records how much electricity your site uses in every 30-minute period and sends those readings remotely, so your supply can be settled on what you actually used in each half hour rather than on an estimate.

“Settlement” is the behind-the-scenes process that squares up what your supplier bought on the wholesale market with what its customers used. Ofgem explains that this comparison is done for each half-hour period of the day.

Most sites have not historically had meters that could measure each half hour. Their use has been estimated using standard load profiles. Elexon, which runs settlement, builds those profiles from a sample of half-hourly metered sites across eight profile classes, with a target sample of 2,500 customers across the whole country.

What does profile class 00 mean on my MPAN?

The first two digits of the top line of your MPAN (the “supply number” on your bill) are the profile class. Ofgem’s guidance for businesses tells you to look at the two-digit number in the box to the right of the “S”.

• 01 to 08 are the eight estimated profiles. 01 and 02 are domestic, 03 and 04 are non-domestic unrestricted and Economy 7 supplies, and 05 to 08 are non-domestic maximum demand customers.
• 00 has traditionally meant there is no profile at all, because the site is metered and settled half-hourly.

That meaning is shifting. Under the supply number format Ofgem approved for market-wide half-hourly settlement (REC change R0083), the MHHS design stops using profile classes except for legacy non-smart meters. Once an MPAN has migrated and no longer has a profile class, suppliers populate the top line with 00. Profile classes 02 and 04 carry on as before.

The same change replaced the meter timeswitch code with a four-digit Standard Settlement Configuration ID, and the line loss factor class with a DUoS Tariff ID. So a 00 on a recent bill does not always mean you have a traditional HH meter. You can decode the rest of your number with our MPAN checker.

When is a half-hourly meter mandatory?

Three sets of rules have pushed business sites onto half-hourly metering and settlement.

Sites with demand over 100kW

The Balancing and Settlement Code (BSC) defines a “100kW Metering System” as one where the average of the maximum monthly demands in the three highest months of the last twelve exceeds 100kW. Elexon classes the metering at these sites as Measurement Class C: half-hourly metering equipment at above 100kW premises.

National Grid Electricity Distribution’s customer guide adds that if your capacity requirement is above 100kW you will generally need an agreement with the appointed meter operator for a set period, at an extra charge, with a possible exit fee if you end it early.

Profile classes 05 to 08 (P272)

Since 6 April 2014, meters in profile classes 5 to 8 have had to be advanced meters that can be read remotely and record half-hourly consumption. BSC modification P272 then made half-hourly settlement mandatory for these sites from 1 April 2017.

A related change, P322, required suppliers to move profile class 5 to 8 customers onto half-hourly settlement within 45 days of a new or renewed contract from 5 November 2015. Ofgem’s guidance is clear that you cannot choose to stay non half-hourly settled if you are in these classes and have an advanced meter.

CT-metered advanced meters (P432)

BSC modification P432, implemented on 15 April 2024, set explicit rules for current transformer (CT) advanced meters. Any still settling non half-hourly must move across by MHHS milestone M14, which Elexon lists as October 2026.

What is market-wide half-hourly settlement (MHHS)?

MHHS is the industry programme moving every electricity meter in Great Britain, including smart, non-smart, advanced and unmetered supplies, onto settlement using half-hourly data. Ofgem decided to go ahead in 2021, estimating net benefits to consumers of £1,559 million to £4,509 million over 2021 to 2045.

Ofgem appointed Elexon to lead delivery. The original plan finished in October 2025, but in November 2024 Ofgem approved a change request (CR055) that pushed the programme back by 6.5 months.

What is the MHHS timetable?

Date	Milestone
22 September 2025	Elexon’s new central systems go live (M10 approved on 24 September)
22 October 2025	Suppliers start migrating meters (M11 and M12)
2026	MHHS Programme reports 50% of all industry MPANs migrated
October 2026	M14: qualified participants authorised to operate under MHHS; about 80% of meters expected to have migrated
May 2027	M15: migration complete
July 2027	M16: cutover to the new settlement timetable

Elexon puts the job at around 33 million meters over an 18-month migration period, coordinated through a Migration Control Centre working with suppliers. Once cutover is done, Elexon says settlement will be completed in four months instead of 14.

Does my business need to do anything?

Migration is carried out by suppliers and their agents, so it is not something you apply for. What changes is how your supplier’s costs are calculated. Ofgem expects MHHS to give suppliers reasons to offer new products such as time-of-use tariffs, and Elexon says the data also supports demand-side response.

If you are offered a new tariff type at renewal, check the terms carefully and compare it with a standard contract. Our guide to fixed vs flexible contracts covers the basics.

What’s on a half-hourly electricity bill?

Larger half-hourly sites usually see more lines on their bill than a small shop or office. Northern Powergrid explains that for industrial and commercial customers its charges may be identifiable on the bill, and are made up of a daily fixed charge, time-of-use unit charges, a charge for the capacity reserved on its network, and reactive power charges. For small businesses these network charges are generally built into the prices you pay.

These charges come from your distribution network operator (DNO) and are passed through by your supplier. See what is a DNO for who runs your area.

Component	Unit	What it covers
Red, amber and green unit charges	p/kWh	Network use, priced by time of day
Fixed charge	p per MPAN per day	A daily standing element
Capacity charge	p/kVA/day	The Maximum Import Capacity (MIC) reserved for you
Excess capacity charge	p/kVA/day	Demand above your agreed MIC
Reactive power charge	p/kVArh	Reactive power outside a 0.95 power factor

Your supplier’s own energy prices and taxes such as the Climate Change Levy sit on top of these.

Red, amber and green time bands

Distribution use of system (DUoS) unit charges vary by time of day. Red is the peak, highest-priced band, green the lowest and amber sits between. The exact hours differ between distributors and are set out in each DNO’s charging statement. National Grid Electricity Distribution’s guide describes its red period as weekday early evening.

Because these bands are only visible in half-hourly data, a site that moves heavy use out of the red band can see lower network costs.

Capacity (kVA) and your MIC

Your MIC is the capacity your DNO has reserved for you, and the capacity charge is based on it whether you use it or not. Ofgem’s guidance suggests contacting your DNO if you think your MIC is too high.

National Grid Electricity Distribution’s guide sets out its own rules:

• No reduction is allowed for 12 months after an MIC is agreed, and reductions are allowed only once in any 12-month period.
• Capacity you give back may be used elsewhere, so getting more later could mean paying for network reinforcement.
• Exceeding a reduced MIC triggers an excess capacity charge, which it says is typically two or three times the base capacity rate.

Reactive power

Reactive power charges apply to half-hourly metered connections. Motors, transformers and fluorescent lighting can cause a poor power factor. National Grid Electricity Distribution says these charges are generally avoidable if the installation keeps a power factor between 0.95 and unity, which power factor correction equipment can help with.

Who needs a half-hourly quote?

You will generally be looking at half-hourly contracts if:

• your site’s maximum demand is over 100kW, or it has a CT meter
• your MPAN shows profile class 05 to 08, or a traditional 00 half-hourly supply
• your current bill shows capacity (kVA), time-band DUoS or reactive power charges

If you are not sure, check your bill against the table above. Smaller sites whose MPAN has simply migrated under MHHS will not usually see these extra lines.

What to have ready

• Your MPAN and your agreed MIC.
• Your half-hourly consumption data. Since 1 December 2022, non-domestic customers of any size can ask their supplier for up to 12 months of historic smart or advanced meter data free, and suppliers must respond within 10 working days.
• Your contract end date and any notice period (see contract renewal).
• A letter of authority if a broker is gathering data for you.

Having the data to hand lets anyone quoting see when you use power, which matters because network charges vary by time band. For groups with several large sites, our multi-site guide covers managing contracts together.

Can I appoint my own meter operator and data collector?

Yes. Ofgem’s guidance says suppliers appoint agents to install and maintain your meter and collect and process your data, but there is no reason you cannot appoint your own. It suggests shopping around for half-hourly qualified agents and checking their contract length matches your supply contract. Under MHHS these roles are being renamed: the REC now refers to a Metering Service and a Data Service rather than a meter operator and data collector.

Frequently asked questions