Half-Hourly Meters Explained

What Does a Half-Hourly Meter Actually Do?

A standard business meter keeps a running total. Someone (or something) reads it, and the industry then estimates how that total was spread across the day using a standard shape for customers like you. A half-hourly meter doesn’t need the guesswork. It stores a reading for each half-hour, and a data service retrieves those readings and passes them into settlement, the process that works out who supplied what and who pays for it.

Elexon, which runs electricity settlement in Great Britain, sorts metering into “measurement classes” by how consumption is measured. Non-half-hourly meters are class A. Half-hourly metering at premises above 100kW is class C, and half-hourly metering at premises below 100kW is classes E, F and G, split by whether the meter uses current transformers and whether the premises are domestic. So half-hourly metering isn’t one product. It’s a way of measuring that covers everything from a factory’s high-voltage supply to a small shop with a smart meter.

Why should you care? Because the half-hourly readings are what your supplier is charged on. Network charges for half-hourly metered sites change by time of day. On National Grid Electricity Distribution’s network, for example, DUoS charges come in red, amber and green time bands, with red covering the weekday early evening peak. If your usage is measured half-hour by half-hour, the price you’re quoted can reflect when you really use power, not an average, and that’s exactly what we look at when we compare prices for you.

Does Your Site Need a Half-Hourly Meter?

The 100kW line goes back a long way. It was written into the Electricity Act in 1989, and deciding whether a site is over or under it has always needed some interpretation. If your site’s demand is above 100kW, you’ll be in half-hourly metering already.

Below 100kW, half-hourly settlement has spread in stages. P272 brought maximum demand sites across in 2017. Then modification P432, approved by Ofgem, means current transformer (CT) advanced meters have to be settled half-hourly by MHHS milestone M14, which the MHHS Programme says was delivered on time on 28 October 2026. CT meters measure the supply through current transformers rather than carrying the whole current through the meter.

So do you need one? If your site is above 100kW or has a CT advanced meter, it’ll already be half-hourly settled, and under MHHS every remaining site is moving onto half-hourly settlement too. Not sure where your sites sit? Send us a recent bill and our Energy Team will tell you.

What Does Profile Class 00 Mean?

Before half-hourly settlement, every non-half-hourly supply was given a profile class: a two-digit code telling the industry which standard usage shape to apply. There are eight:

• Profile classes 1 and 2: Domestic customers, on an unrestricted supply (1) or an Economy 7 type off-peak tariff (2).
• Profile classes 3 and 4: Non-domestic customers, on an unrestricted supply (3) or an off-peak tariff (4).
• Profile classes 5 to 8: Maximum demand customers, grouped by peak load factor, from below 20% (5) to above 40% (8).

A half-hourly settled supply doesn’t need a usage shape, because its real half-hourly readings are used instead. That’s what profile class 00 tells you. Under the MHHS supply number format, the profile class stays on the top line of your supply number, the MPAN printed on your bill, and any migrated MPAN without a profile class shows “00”. Supplies with a profile class of 02 or 04 keep their code.

P272: When Maximum Demand Meters Went Half-Hourly

P272 is history, but it’s the reason so many business sites changed. It was the industry rule change that made half-hourly settlement mandatory for profile classes 5 to 8, and it took effect in April 2017. Maximum demand sites without a half-hourly meter can only use historic load profiles because, as of October 2026, Elexon updates load profiles for profile classes 1 to 4 only.

If your site moved across under P272, you’ll have seen the change in your bills. Half-hourly metered connections pay network charges by time band, plus a capacity charge in pence per kVA per day based on the site’s agreed capacity. We check both on your bills for you.

What Does MHHS Change?

MHHS takes the half-hourly approach and applies it to every meter. Here’s the MHHS timeline in brief: suppliers began migrating meters on 22 October 2025, full migration is due to finish on 7 May 2027 (milestone M15), and on 2 July 2027 (milestone M16) the industry cuts over to a shorter settlement timetable, with settlement taking about four months instead of 14.

The familiar agent roles are changing too. Under MHHS, the Metering Service (Advanced) installs and maintains meters in the advanced segment, and the Advanced Data Service retrieves and processes their readings, taking over from the meter operator and data collector roles. That’s work for your supplier and its agents, so there’s nothing you need to sign. You may just see the new names in contract packs and on bills, along with a slightly different top line on your supply number. If anything looks unfamiliar, give us a call and we’ll talk you through it.