Smart Meters in Great Britain: What They Do (and What They Don't)
Over 35 million smart meters have now been installed across Great Britain. Yet many households with smart meters still don't know what they can actually do — or aren't taking advantage of the most useful features.
Smart meters are the foundation of the smart energy system that makes Octopus Agile, time-of-use tariffs, and home energy optimisation possible. This guide explains what they are, how they work, and how to use them to your advantage.
What Is a Smart Meter?
A smart meter is a digital electricity (and usually gas) meter that replaces the older mechanical meter in your home. Unlike traditional meters, which require a meter reader to physically visit and check a spinning dial, a smart meter:
- Records consumption in 30-minute intervals rather than a single daily or monthly total
- Transmits this data wirelessly to your energy supplier via the Smart Metering Wide Area Network (SMWAN)
- Communicates with your In-Home Display (IHD) — a small screen that shows real-time usage and cost
- Enables remote switching — your supplier can change your tariff rates without visiting your home
SMETS1 vs SMETS2: The Upgrade That Mattered
Early smart meters (SMETS1, installed 2013–2018) had a major flaw: they only "worked smart" with the supplier that installed them. If you switched supplier, the meter often reverted to dumb mode, requiring manual readings again.
SMETS2 meters, rolled out from 2018 onwards, use a centralised Data Communications Company (DCC) network. This means:
- They work smart with any supplier — switching doesn't break them
- Half-hourly data is accessible to any licensed supplier you switch to
- Remote updates and tariff changes are possible without an engineer visit
If you have a SMETS1 meter, your supplier may have remotely upgraded it to behave like SMETS2 via a firmware update — most have been migrated.
What Data Does Your Smart Meter Collect?
Your smart meter records electricity consumption in 30-minute intervals (half-hour periods). This creates a detailed profile of your daily usage — when you're home, when major appliances run, and how your consumption varies seasonally.
This data is used by:
- Your supplier: For accurate billing, tariff design, and time-of-use pricing
- Grid operators: Aggregated anonymised data helps National Grid ESO understand demand patterns
- You: Via your IHD, your supplier's app, or third-party tools
You can choose how much historical data your supplier shares — you can opt for daily totals only, or full 30-minute data. Opting in to 30-minute data sharing is required for time-of-use tariffs like Octopus Agile.
The IHD: More Useful Than Most People Think
The In-Home Display (IHD) that comes with your smart meter shows:
- Real-time power consumption (watts) — watch it jump when you turn on the kettle
- Cost per hour at current usage
- Daily, weekly, and monthly totals
- Traffic light indicator — green (low use), amber (medium), red (high)
Most people glance at it once and put it in a drawer. But the IHD is genuinely useful for:
- Finding energy hogs: Turn on the oven, check the watt reading. Turn on the tumble dryer. Understand which devices actually cost money
- Understanding standby load: Check the IHD when "nothing is on" — if it reads 200W+, something is drawing significant standby power
- Validating efficiency improvements: Check before and after switching from an old boiler to a heat pump, or adding loft insulation
Smart Meters and Time-of-Use Tariffs
Smart meters are the prerequisite for time-of-use tariffs. Without half-hourly metering, a supplier can't charge you different rates at different times of day — they have no way of knowing when you used the electricity.
With SMETS2 and half-hourly data sharing enabled, you can access:
- Octopus Agile: Half-hourly prices matching the wholesale market — the most sophisticated time-of-use tariff available
- Octopus Flux: A solar export and import tariff with structured time-of-use pricing
- Octopus Go: Fixed cheap overnight rate (typically 7.5p/kWh) for EV charging, 2 standard rates otherwise
- Octopus Cosy: Cheap "cosy hours" 4 times per day, designed for heat pumps
- E.ON Next Drive: Similar overnight EV charging tariff
- Economy 7/10: Older tariffs using simple time switches rather than half-hourly metering
The Market Prices dashboard shows how wholesale electricity prices vary throughout the day — the same signal that drives Agile tariff pricing.
What Smart Meters Don't Do
Despite the name, smart meters have some important limitations:
They don't show per-appliance consumption — the meter reads total household consumption. To understand individual appliance usage, you need a separate energy monitor (Emporia, Shelly EM, etc.) installed at the fuseboard.
They don't control anything — a smart meter alone doesn't switch appliances on or off, schedule your EV charger, or manage your battery. These are separate smart home devices that respond to signals from apps and tariff integrations.
They don't guarantee smart tariffs automatically — you need to actively switch to a time-of-use tariff and enable half-hourly data sharing with your supplier. Simply having a smart meter doesn't change your pricing.
SMETS1 meters may have limited functionality — if your meter is older and shows symptoms of dumb mode (supplier has to estimate bills, IHD stopped working after a switch), contact your supplier about a SMETS2 upgrade.
Getting the Most From Your Smart Meter
- Enable half-hourly data sharing with your supplier (usually in your online account settings) — required for time-of-use tariffs
- Download your supplier's app and look at your consumption patterns — most suppliers now show half-hourly usage graphs
- Consider switching to a time-of-use tariff if you have any flexible loads (EV, battery, heat pump, flexible washing/dishwasher habits)
- Use the IHD to understand your home's energy profile — even a few minutes of investigation reveals useful information
- Compare your usage year-on-year in the app — see how changes like insulation, appliance upgrades, or habit changes affect consumption
Smart Meters and the Energy Transition
At a grid level, smart meters are infrastructure for the future:
- They allow demand flexibility — suppliers can offer incentives to shift consumption during grid stress events
- They support peer-to-peer energy trading and community energy schemes
- They enable accurate forecasting of demand patterns, improving grid stability
- They make half-hourly settlement of the electricity market possible — the foundation for aligning retail prices with grid conditions
Great Britain completed its transition to half-hourly settlement in 2024, meaning smart meters are now a genuine part of how the grid is managed — not just convenient billing tools.
Summary
- SMETS2 meters record 30-minute consumption and work with any supplier
- The IHD shows real-time usage — useful for identifying energy hogs and standby loads
- Half-hourly data sharing must be enabled to access time-of-use tariffs like Octopus Agile
- Smart meters don't control appliances or guarantee savings — but they enable the tools that do
- Wholesale electricity prices vary significantly through the day — see the live view at Market Prices