What is half-hourly electricity?

The short answer

A half-hourly (HH) electricity supply has a meter that records how much electricity your site uses in every 30-minute period of the day. That is 48 readings a day and 17,520 a year (17,568 in a leap year). The readings are collected remotely, usually every day, so there are no manual meter reads and no estimates when the data flows properly.

Those readings are used in two ways. Your supplier uses them to bill you, and the industry uses them to settle – to work out how much electricity your supplier had to buy for you in each half hour. Because cost depends on when you use power, a half-hourly supply prices your actual pattern of use rather than an average.

How a half-hourly meter works

Half-hourly sites have an advanced meter – an AMR (automatic meter reading) meter, or for larger supplies a CT (current transformer) meter, where the supply is too big to pass straight through the meter. The meter stores each half hour’s reading and a communications link sends the data to a data service, which checks it and passes it on for billing and settlement.

Two companies sit alongside your supplier:

• The metering service installs and maintains the meter (traditionally called the Meter Operator, or MOP).
• The data service collects and checks the readings (traditionally the Half-Hourly Data Collector, HHDC).

Under Market-wide Half-Hourly Settlement these roles are being renamed: the metering role for advanced meters becomes Metering Service Advanced (MSA) and the data role becomes the Advanced Data Service (ADS). If either contract lapses, data can stop flowing and bills can fall back on estimates. Metering and data service contracts explains what to check.

Who has to be half-hourly?

There are three routes onto a half-hourly supply.

Sites over 100 kW

If a site’s maximum demand is over 100 kW in any half hour, the Balancing and Settlement Code requires it to be half-hourly metered and settled. These are profile class 00 sites. Note that this is a demand rule measured in kW, not an annual consumption rule in kWh – a common misunderstanding. A busy factory, cold store, hospital or large office often goes over it; a site that uses a lot of energy steadily at low power might not. Our guide to the 100 kW rule goes into detail.

Profile classes 05 to 08 (P272)

Industry change P272, fully in force from April 2017, moved larger non-domestic sites with maximum demand meters – profile classes 05 to 08 – onto half-hourly settlement. Many medium-sized businesses became half-hourly then without changing anything on site.

Everyone else (MHHS)

Market-wide Half-Hourly Settlement is moving every meter in Great Britain to half-hourly settlement, with a deadline of May 2027. Understanding MHHS explains what that means for you.

How to tell if your site is half-hourly

Look for the box marked “S” on your bill: that is your MPAN (Meter Point Administration Number). The first two digits of the top line are the profile class – 00 means half-hourly. The first two digits of the bottom line are the distributor ID, which tells you which electricity network region you are in. Our home page has a quick MPAN checker.

Other clues on a half-hourly bill: an Agreed Supply Capacity in kVA, a capacity charge, unit rates split into red, amber and green bands, and charges for reactive power.

What is on a half-hourly bill

The biggest difference between a half-hourly bill and a standard business bill is how much of it is not the energy itself:

• Energy charges – the commodity, per kWh.
• DUoS (Distribution Use of System) – unit charges in red, amber and green time bands, a fixed daily charge, a capacity charge per kVA of Agreed Supply Capacity, excess capacity charges and reactive power charges.
• TNUoS (transmission) – since April 2023 mostly a fixed daily charge based on your site’s band.
• BSUoS and policy costs – balancing, Contracts for Difference, the Renewables Obligation, Feed-in Tariffs and the Capacity Market.
• Metering and data charges.
• Climate Change Levy – 0.801p per kWh for electricity from 1 April 2026 (8% of that for sites with a Climate Change Agreement) – and VAT.

Each of these can be wrong, and several can be reduced. How to read a half-hourly bill goes through them line by line.

Why timing matters

Network operators charge more for electricity used when the network is busiest. The red band – usually late afternoon on weekdays – can cost many times more per kWh in DUoS than the green band overnight and at weekends. Each of the 14 network regions sets its own times. With half-hourly data you can see exactly how much of your use falls in each band and whether any of it could move. Read more in DUoS red, amber and green bands.

Does half-hourly cost more?

Not in itself. A half-hourly supply prices your real pattern of use. Sites that use most of their power at night or at weekends can benefit; sites with heavy red-band use or an oversized capacity can pay more than they need to. The data is what lets you tell the difference.

What to do next

1. Find a recent bill and check the profile class on your MPAN.
2. Note your contract end date and Agreed Supply Capacity (kVA).
3. Send it to us for a free half-hourly bill check, or call 07565 147 170.

Frequently asked questions

What does half-hourly electricity mean?

It means your electricity is metered, settled and billed in 30-minute periods. The meter records 48 readings a day and sends them remotely, so your bill reflects exactly when you used power rather than an estimate or an average profile.

Is the half-hourly threshold 100,000 kWh a year?

No. The mandatory threshold is a maximum demand of more than 100 kW in any half hour (profile class 00). It is about how much power you draw at once, not how many kWh you use over a year. P272 and MHHS have since moved other business sites to half-hourly settlement too.

How do I know if my meter is half-hourly?

Look at the S box (MPAN) on your bill. If the first two digits of the top line are 00, your supply is half-hourly. Bills that show a kVA capacity, a capacity charge or red, amber and green unit rates are also half-hourly.