Smart meters and half-hourly data
Guide · updated 2026-08-23
A smart meter can record your consumption in half-hour blocks — 48 numbers a day. It is the difference between a bill you have to trust and one you can check.
Daily, half-hourly, or neither
Smart meters have a consent setting for how often readings are shared: monthly, daily, or half-hourly. It defaults conservatively, so plenty of people with a smart meter have no half-hourly data at all and do not know it.
Half-hourly consent is required for any half-hourly-settled tariff — you cannot be billed for Agile without it. Suppliers let you change the setting in the app or on request, and it takes effect within a day or two. It is not retrospective: turning it on today does not create last month's data.
SMETS1 and SMETS2
First-generation SMETS1 meters were tied to the supplier that installed them and often went "dumb" on a switch, though most have now been migrated to the national DCC network and work again. SMETS2 meters are supplier-agnostic by design and keep working through a switch.
The practical difference for data: a SMETS1 gas meter commonly reports in kWh while a SMETS2 gas meter reports in cubic metres, and anything reading that data has to detect which. Get it wrong and the figures are out by a factor of about eleven — see gas rates for the conversion.
Why the data is a day or two behind
Readings travel from the meter to the DCC and then to your supplier, and that pipeline runs on a schedule rather than instantly. One to two days of lag is normal and not a fault. Prices, by contrast, are published a day ahead — so you always know tomorrow's prices before you know yesterday's usage.
That is also why usage history on this site fills in gradually after you connect rather than appearing all at once: the first import seeds about a month, then the backfill creeps steadily back through the year.
What half-hourly data lets you see
A daily total tells you that you used 12 kWh. Half-hourly data tells you that 4 kWh of it went in the evening peak, which is the number that decides whether a time-of-use tariff will save you money. It also makes standby draw visible as a flat baseline at 03:00, and shows exactly what an immersion heater or a shower costs.
Common questions
How do I turn on half-hourly readings?
Change the meter reading frequency consent with your supplier, usually in their app or by asking. It takes a day or two to take effect and is not backdated.
Why is my smart meter data one or two days behind?
Readings pass from the meter through the DCC network to your supplier on a schedule rather than in real time. A lag of one to two days is normal.
What is the difference between SMETS1 and SMETS2?
SMETS1 meters were tied to the installing supplier and often lost functionality on a switch, though most have since been migrated. SMETS2 meters work with any supplier by design.
See it on your own numbers. halfhourly.uk shows live half-hourly prices for every GB region for free, and if you connect an Octopus account it prices your own smart-meter readings against every tariff.