What is a half-hourly meter (and what P272 means)

A half-hourly meter is an electricity meter that records how much power a site uses in every half hour of the day and passes those readings on for settlement, the process by which a supplier is charged for the energy a site draws. Most larger commercial and industrial sites have one. If your site has recently moved onto, or has been described as being on, a half-hourly meter, the readings it produces are the exact record a solar and battery feasibility study is built from. The change that moved a large band of mid-size sites onto half-hourly settlement was called P272, approved by Ofgem on 29 October 2014 and in force from 1 April 2017, the dates recorded in Elexon's page on the P272 modification.

What is a half-hourly meter?

A half-hourly meter measures the electricity flowing into a site and stores a separate reading for each 30-minute period. Over a year those readings build into a continuous record of demand, one value after the next, which is why a single year's file is enough to describe how a site uses electricity across the whole year. The way that file is laid out, and what its numbers reveal about peak demand and load shape, is covered in how to read half-hourly electricity data.

The alternative is a non-half-hourly meter, read only at intervals, often quarterly, from which a site's half-hourly shape is estimated against a standard profile rather than measured directly. For a small shop or office that estimate is accurate enough for billing. A site large enough to consider solar or storage needs more than that, because the value of both depends on the timing of demand, which only a measured half-hourly record carries.

How do I know if my site is on one?

Non-domestic sites are grouped into profile classes. The largest, with a maximum demand of 100 kW or more, have long been metered and settled half-hourly and sit outside the profile classes; the profiling sample that builds the standard profiles covers customers below that level, as Elexon's description of the profile classes sets out. Smaller maximum-demand sites fall into profile classes 5 to 8, graded by their peak load factor: class 5 for a load factor below 20 per cent, classes 6 and 7 for the bands up to 40 per cent, and class 8 above 40 per cent, in the same Elexon description. The load factor is the average demand as a proportion of the peak, so a site that runs steadily sits in a higher class than one with sharp peaks.

A site in profile classes 5 to 8 is the mid-size band that P272 moved onto half-hourly settlement. If you are unsure which class a site sits in, the supplier or the meter operator can confirm it, along with whether the meter installed is capable of recording half-hourly data.

What did P272 change?

Until the P272 reform, a site in profile classes 5 to 8 could be settled on an estimated profile even where the meter fitted was capable of recording half-hourly data. P272 required those sites, where such metering had been installed, to be settled on their actual half-hourly readings. Ofgem approved the change on 29 October 2014, first for a 2016 start, and after a one-year extension requested through the industry panel the final compliance date became 1 April 2017, the dates set out by Elexon. From that point a large population of mid-size commercial sites began producing a reading for every half hour of the year.

P272 settled that mid-size band, and the reform now extending the same half-hourly basis to homes and the smallest businesses is market-wide half-hourly settlement, set out in market-wide half-hourly settlement. A site already settled half-hourly after P272 is unaffected in how its own energy is settled by that later change.

What a half-hourly meter means for solar and storage

Because a half-hourly meter records the timing of a site's demand, each half hour separately rather than a quarter's total, it captures what decides the value of on-site solar and a battery. The single highest reading in the year is the site's peak demand, which drives the import capacity the connection needs. The time stamp on each reading shows how much of the demand lands in the expensive network and tariff windows, which is where a battery lowers the cost by shifting demand out of those periods, including through the P415 route to wholesale value. An annual or quarterly total cannot answer those questions, because it records the quantity without the timing.

So the moment a site moves onto a half-hourly meter, it starts to hold the one dataset a feasibility study needs. Lupa takes that half-hourly file together with the site's electricity invoice and turns them into a feasibility report, and the platform reads the file's peaks, load shape and tariff bands to model how solar and storage would perform against the site's real demand.