What is half-hourly metering? A plain-English guide for UK businesses

A half-hourly meter records how much electricity your site uses in every 30-minute period of every day, and that data is collected remotely rather than read by someone on site. If your business has one, your bills, your contract prices and many of your network charges are calculated from that detailed record. This guide explains how half-hourly metering works, who needs it and what you can check on your own bill.

Key points

• A half-hourly (HH) meter records 48 readings a day: 17,520 in a normal year and 17,568 in a leap year.
• Sites whose maximum demand is over 100 kW in any half-hour must be half-hourly metered and settled. It is a kW demand threshold, not an annual kWh figure.
• If the top line of your MPAN starts with 00, your site is settled half-hourly.
• Your half-hourly data shows exactly when you use power, which is the starting point for cutting cost.

How a half-hourly meter works

The electricity market in Great Britain runs in 30-minute blocks called settlement periods. A half-hourly meter stores a reading for each one, so a day produces 48 readings and a year produces 17,520 (17,568 in a leap year). The meter is read remotely, usually once a day, and the data is passed on for billing and settlement.

On larger sites the meter is usually current transformer (CT) operated. The CTs sit around the incoming cables and step the current down to a level the meter can measure safely. Smaller supplies may use a whole-current meter, where the supply runs directly through the meter.

Many half-hourly meters record reactive energy (kVArh) as well as active energy (kWh). Reactive energy does no useful work, but it still loads the network. It is used to work out your power factor and any reactive power charges.

Why half-hourly data changes how you are billed

Suppliers buy electricity to cover their customers' demand in every half-hour. When a site is not settled half-hourly, its consumption is spread across the day using a standard profile: an estimated shape based on the type of customer. When a site is settled half-hourly, the supplier knows exactly what you used in each period. That has three practical effects:

• Contract prices reflect your real profile. A site that uses most of its power overnight is priced differently from one that peaks in the early evening.
• Network charges vary by time. Distribution charges are split into red, amber and green time bands, so timing affects cost. Our guide to DUoS red, amber and green bands explains how.
• Bills are based on measured data. As long as the meter is communicating, there should be little need for estimated readings.

Who needs a half-hourly meter

There are three routes onto half-hourly settlement.

Sites over 100 kW

Under the Balancing and Settlement Code, a site whose maximum demand is over 100 kW in any half-hour must be half-hourly metered and settled. These sites are profile class 00. People often misquote this as a 100,000 kWh a year rule, which it is not. We cover the detail in our guide to the 100 kW rule.

Former maximum demand sites (P272)

BSC modification P272, fully in force from April 2017, moved profile class 05 to 08 sites (larger non-domestic sites with maximum demand meters) to half-hourly settlement.

Everyone else, through MHHS

Market-wide Half-Hourly Settlement (MHHS) is Ofgem's programme, run by Elexon, to move every meter in Great Britain to half-hourly settlement. Suppliers began migrating meters on 22 October 2025 and the full migration deadline is May 2027. Our MHHS guide for businesses sets out the timeline, and Elexon publishes progress on its MHHS programme pages.

Being settled half-hourly through a smart meter is not quite the same as having a traditional half-hourly supply. Larger sites still use advanced metering, which under MHHS is looked after by a Metering Service Advanced (MSA) and an Advanced Data Service (ADS).

How to tell if your site is half-hourly

You can usually confirm this from a recent bill in a few minutes. Check for the following:

• The MPAN. Your 21-digit Meter Point Administration Number is printed on the bill. If the first two digits of the top line are 00, the site is half-hourly. The bottom line starts with a two-digit distributor ID that shows your network region. For example, 15 is Northern Powergrid North East and 23 is Northern Powergrid Yorkshire.
• Time-banded network charges. DUoS unit rates shown as red, amber and green.
• A capacity figure in kVA. A line for Agreed Supply Capacity (ASC) with a daily capacity charge.
• Metering and data charges. Separate charges for a meter operator and data collection, or for the new MSA and ADS roles.
• Reactive power charges. A line in kVArh, which only appears where reactive energy is measured.

If you are still not sure, ask your supplier to confirm the profile class and send you a copy of your half-hourly consumption data.

What your half-hourly data can tell you

Half-hourly data is one of the most useful sets of energy information a business has, yet it often goes unread. A simple chart of a typical week will usually show:

• Baseload: what the site draws overnight and at weekends when it should be quiet. Equipment left running shows up here.
• Peaks: the highest half-hours, which drive decisions about supply capacity.
• Red-band use: how much of your consumption falls in the most expensive network period.
• The effect of changes: new machinery, different shift patterns, LED lighting or solar panels.

A useful rule of thumb: double a half-hourly kWh reading to get the average kW across that half-hour. A reading of 60 kWh in one period means the site averaged 120 kW. Comparing your highest half-hours with your Agreed Supply Capacity (after allowing for power factor, because capacity is set in kVA) is often the first step in a capacity review. Our load profile analysis service turns this data into a short list of practical actions.

What it means for your bills and contracts

A half-hourly bill has more lines than a standard business bill. Alongside the energy cost you will see non-commodity charges: DUoS, TNUoS, BSUoS, policy costs such as Contracts for Difference and the Renewables Obligation, metering and data charges, Climate Change Levy and VAT. Our guide on how to read a half-hourly bill takes you through each one.

When you renew, suppliers price your contract using your half-hourly data. A clean, complete data history makes it easier to get accurate quotes and to choose between fixed, pass-through and flexible contracts. It is also worth knowing your contract end date, because out-of-contract rates are usually much higher than contract rates.

Get help with half-hourly metering

If you are not sure whether your site is set up correctly, or you would like someone to look through your half-hourly data and bills, we can help. We compare half-hourly electricity contracts from a range of UK suppliers and check bills for errors. If we can't find a better option, we'll tell you.

Request a free quote or bill check, or call 07565 147 170 to talk it through.

Frequently asked questions

How many readings does a half-hourly meter take?

A half-hourly meter records consumption in each 30-minute settlement period, so it takes 48 readings a day. That is 17,520 readings in a normal year and 17,568 in a leap year. The data is collected remotely, usually once a day, so nobody needs to visit the site to read the meter.

Is a half-hourly meter the same as a smart meter?

Not exactly. Both can record half-hourly data, and under MHHS smart meters are being moved to half-hourly settlement. Larger sites, however, normally use advanced metering, often current transformer operated, with separate metering and data services. Smart meters use the Smart Data Service, while advanced meters use the Advanced Data Service.

How do I know if my business has a half-hourly meter?

Look at the MPAN on your electricity bill. If the first two digits of the top line are 00, your site is half-hourly. Other clues are red, amber and green DUoS charges, a capacity charge in kVA and separate metering and data charges. Your supplier can also confirm it for you.