Half-Hourly, Half-Yours: Taking Your Energy History to the Next Tariff

Switching energy supplier used to be a paperwork ritual: final reading, closing bill, new logo. In 2026, the meter itself is part of the paperwork. If you have a smart meter, it is probably logging your electricity use every 30 minutes — and that half-hourly trail says more about your household than a monthly total ever could. It can show whether you charge an EV overnight, whether the heat pump runs at 6am, whether the tumble dryer is a Sunday habit. That is valuable for planning a tariff. It is also valuable data. The question worth asking before your next deal is not just 'what will this cost?' but 'who keeps the record, and what can they do with it?'

A diary written in 30-minute slices

Your smart meter does not send one vague number to a mysterious cloud. It records consumption at set intervals, and those readings travel through the national smart meter communications network — the Data Communications Company, or DCC — before reaching your supplier. For billing, a supplier may only need a monthly or daily read. For half-hourly settlement, the behind-the-scenes maths that matches what the country used with what was bought, the finer detail matters.

That is why time-of-use tariffs lean on half-hourly data. If you pay less between midnight and 5am, someone has to know how much you actually used in that window. The same record can support flexibility schemes, demand-shifting trials and smart charging. None of that is sinister on its own. But it does mean the meter is no longer just a cash register. It is a logbook.

The access list is longer than the bill

Your supplier is the obvious reader. Behind it, network operators and meter operators have defined roles in keeping the system running. The DCC moves the messages. Third parties — comparison services, energy-management apps, flexibility platforms — should only get your data with consent, and the consent should be specific enough to mean something.

The UK's data access and privacy framework sets out what domestic smart meter data can be used for. Billing and settlement are core purposes. Marketing and wider sharing are not the same thing. In practice, the difference often lives in a privacy notice nobody reads and a settings screen nobody opens. That is not a reason to panic. It is a reason to ask a blunt question before you sign: what exactly am I agreeing to share, with whom, and for how long?

When you switch, history does not always follow

On switch day, your new supplier can take over the supply point and read the meter. That does not mean your old half-hourly history arrives in the new app like a playlist moving between streaming services. Some data flows through industry systems for billing and settlement. Anything beyond that may need a request, and the answer can depend on the supplier, the tariff and the consent you gave.

This is where data portability gets practical. If you have spent two winters on a heat pump tariff, that history is useful when you are choosing the next one. It can show whether an off-peak deal actually suits your routine or just sounds good on a comparison site. Asking for an export is not a niche tech demand. It is the equivalent of taking your bank statements with you when you move accounts.

Moving house is the awkward bit

The meter stays. The account ends. In the rush of a move, it is easy to forget that the energy history attached to the property is not automatically packed in a box. Take a final reading, settle the closing bill and ask your supplier for a copy of your consumption data before the account closes. If you are moving into a new place, ask the current supplier what history exists and how the previous account was closed. You will not get someone else's personal data, but you should understand what the property's record looks like.

The next occupant does not inherit your account, but the supply point has a past. That is normal. What matters is that the handover is clean, the readings are agreed and your own data does not disappear into a filing cabinet you cannot reach.

Consent is a setting, not a ceremony

Most of us tick through privacy notices the way we click 'accept' on a cookie banner. Smart meter data deserves a little more attention. Check whether you have agreed to half-hourly sharing, whether third-party access is switched on and whether marketing permissions have been bundled into something else. If you join a time-of-use tariff, half-hourly data is part of the bargain — you cannot get the off-peak price without the measurement. That is fair enough. The point is to know it.

Consent should also be reversible where the purpose allows. If you stop using an energy app, ask what happens to the data it already collected. If you leave a flexibility scheme, check whether your half-hourly readings keep flowing. These are boring questions until they are not.

Seven questions for the next energy deal

1. What meter readings do you collect from my smart meter, and how often?
2. Do you use half-hourly data for billing, settlement or both?
3. Will my historical consumption move with me when I switch, or do I need to request it?
4. Who else can see my data, and what consent have I given?
5. How long do you keep half-hourly readings after I leave?
6. Can I export my usage history in a usable format?
7. What happens to my data if I move home or join a third-party app?

Check your own paper trail

You can ask your supplier for a copy of your personal data. A subject access request should get a response within a month, and it should cover the account data they hold about you. You can also look at the privacy notice for retention periods and sharing arrangements. If something does not add up, the Information Commissioner's Office is the backstop.

None of this is about refusing to share data. A smart meter that nobody reads is just a plastic ornament. The useful version is one where you know what is being recorded, who benefits and how to take your history with you. Your home's energy record should not become an asset you cannot see, export or challenge. The meter remembers — but you should be able to as well.