A traditional electricity bill tells you how much energy your home used over several weeks or months. Half-hourly smart-meter data goes much further by showing when that electricity was imported from or exported to the grid.
This creates a detailed picture of how electricity moves through your home during the day. It can help you understand your baseline demand, investigate unexpected consumption, compare time-of-use tariffs and see how solar panels, batteries, electric vehicles and heat pumps affect your electricity profile.
However, smart-meter data only shows what happens at the boundary between your home and the electricity grid. It does not automatically reveal which appliance used the electricity or provide a complete picture of everything happening behind the meter.
Half-hourly data at a glance
At a glance
- A normal day contains 48 half-hour periods.
- Each reading records energy in kilowatt-hours, or kWh.
- Import and export are recorded separately.
- Half-hourly information is not the same as live power data.
- The meter records electricity for the whole property.
- It cannot directly identify individual appliances.
- Solar and battery monitoring may be needed to complete the picture.
What is half-hourly smart-meter data?
A smart electricity meter can record the amount of electricity passing through it during each 30-minute period.
Instead of receiving one total for an entire day, you can see 48 separate values:
- 00:00–00:30
- 00:30–01:00
- 01:00–01:30
- continuing through to
- 23:30–00:00
Together, these readings create the home’s daily electricity profile.
A conventional meter might show that a household used 12 kWh during one day. Half-hourly data could reveal that most of this electricity was consumed during an overnight EV charge, during a morning hot-water cycle or across the evening peak.
That timing is important when electricity prices change throughout the day or when the home contains equipment that can store or shift energy.
What does one half-hourly reading mean?
A half-hourly reading normally represents the amount of energy used during that period, measured in kWh. It is not an instantaneous power reading.
For example, if your data shows:
18:00–18:30: 1.5 kWh
the home imported 1.5 kWh of electricity during those 30 minutes.
Because half an hour is 0.5 hours, the average power during that period was:
1.5 kWh ÷ 0.5 hours = 3 kW
This does not mean the home continuously drew exactly 3 kW. It might have drawn 6 kW for 15 minutes and very little electricity for the remaining 15 minutes.
Half-hourly data smooths everything that happened during the period into one energy total. It is therefore excellent for identifying patterns but cannot show every short-lived appliance peak.
Import and export data
- Import
- Electricity drawn from the grid.
- Export
- Electricity sent from the property to the grid.
An electricity smart meter sits at the boundary between your home and the public electricity network. It can record electricity flowing in both directions.
Homes without solar panels or another form of generation will normally only have import consumption to examine.
A home with solar panels may also have export data. This shows how much surplus electricity crossed the meter and entered the grid, but it does not show the system’s total solar generation.
If the solar panels generated 4 kWh and the home used 3 kWh directly, only the remaining 1 kWh would be exported. The smart meter would see the 1 kWh export, while the solar inverter would record the complete 4 kWh of generation.
This distinction becomes particularly important when batteries are involved.
Half-hourly data versus live electricity data
Half-hourly data is sometimes described as real-time data, but the two are different.
Your supplier’s half-hourly history normally shows energy consumed during completed 30-minute periods. It may not appear in the supplier’s account until the following day or later.
An in-home display or compatible Consumer Access Device can receive much more frequent electricity information through the smart meter’s Home Area Network.
| Data source | Typical level of detail | Most useful for |
|---|---|---|
| Supplier account or download | 30-minute periods | Historical patterns and tariff analysis |
| In-home display | Near-real-time readings | Seeing immediate household demand |
| Consumer Access Device | Frequent electricity updates | Detailed monitoring and automation |
| Solar inverter platform | Device dependent | Solar generation and inverter output |
| Battery platform | Device dependent | Charging, discharge and state of charge |
| EV charger platform | Charging sessions | Vehicle charging consumption |
| Heat-pump monitoring | Device dependent | Heating and hot-water electricity use |
Use half-hourly data when you want to understand patterns over days, weeks or months. Use live monitoring when you want to see what happens as equipment switches on or off.
How to access your half-hourly data
The exact route depends on your supplier and the equipment installed in your home.
Check your supplier's app or online account
Look for sections labelled:
- Energy use
- Usage
- Energy history
- Smart-meter data
- Electricity insights
- Download data
- Export data
Some suppliers provide a detailed chart but no obvious download. Others allow customers to export readings as a CSV or spreadsheet file.
Import and export may be shown in different parts of the account, particularly when different companies provide the household’s import tariff and Smart Export Guarantee arrangement.
Check the meter's reading frequency
A smart meter may be capable of recording half-hourly data without the supplier presenting that information clearly in its customer account.
Ask your supplier whether:
- the meter is communicating correctly;
- half-hourly electricity readings are being collected;
- half-hourly sharing is enabled;
- import and export readings are available;
- the information can be downloaded.
Current data-sharing arrangements depend partly on when the meter was installed and whether the customer has switched supplier or agreed a new contract since 3 November 2022.
Ofgem explains that affected domestic customers are generally set to half-hourly sharing for regulated purposes by default but can normally request daily sharing instead. Older arrangements may differ.
Request the information directly
If the account does not provide a clear answer, ask the supplier:
Please confirm whether you are receiving half-hourly electricity readings from my smart meter and whether I can view or download my import and export data.
It is worth asking specifically about a download. A supplier may possess the information without displaying all of it in the customer-facing app.
In-home displays and connected devices
An in-home display receives information locally from the smart-meter system and can show current electricity use and estimated cost.
A compatible Consumer Access Device can also connect to the Home Area Network. Depending on the service, this may provide more frequent data, online history and integrations with home-energy platforms.
Third-party services normally need the bill payer’s permission before accessing smart-meter consumption data.
How to read a daily electricity profile
A graph containing 48 bars can initially look complicated, but it becomes much easier to understand when it is divided into a few basic features.
Start with the overnight baseline
Look at the quietest part of the night, excluding any deliberate EV or battery charging.
The electricity being used during this period may include:
- Refrigeration
- Routers and network equipment
- Standby loads
- Security equipment
- Pumps and controls
- Mechanical ventilation
- Aquariums or specialist equipment
- A heat pump maintaining the building temperature
The lowest repeated overnight demand provides an indication of the home’s baseline consumption.
A baseline of 0.15 kWh in every half-hour period is equivalent to an average continuous demand of approximately 300 W. Across a full day, that would use around 7.2 kWh if it remained unchanged.
The half-hourly information cannot identify the equipment responsible, but it can show whether the baseline is large enough to justify further investigation.
Look for peaks and sustained loads
A single high period may have been caused by several appliances operating together. A block of consecutive high readings usually suggests a longer-running load.
Examples include:
- A short cooking-related peak
- An immersion-heater cycle
- Several hours of EV charging
- A battery charging from the grid
- Electric space heating
- A heat pump operating during cold weather
Repeated patterns at approximately the same time each day are particularly useful because they may correspond with programmed schedules.
Compare similar days
One isolated day can be misleading. Compare:
- Weekdays with other weekdays
- Weekends with weekends
- Occupied and unoccupied days
- Mild and cold days
- Summer and winter
- Days before and after changing a control setting
Patterns become more reliable when they recur.
Remember that the smart meter measures the whole property. A recognisable shape may strongly suggest what happened, but it does not prove which individual appliance caused it.
How different technologies appear in the data
Half-hourly information becomes particularly valuable when the home has several electrical technologies interacting with one another.
Solar panels
Solar panels can reduce grid imports during daylight hours and create export when generation exceeds the combined needs of the home and battery.
Possible signs include:
- Lower grid imports during the middle of the day
- Periods with no grid import
- Daytime electricity export
- Much greater export during spring and summer
- Lower daytime imports on sunny days than cloudy days
However, the smart meter cannot show total solar generation.
Example
Imagine the following half-hour:
- Solar generation: 2.0 kWh
- Household demand: 1.2 kWh
- Grid export: 0.8 kWh
The smart meter records the 0.8 kWh exported. It does not directly record the 1.2 kWh of solar electricity used inside the home.
To understand total generation and self-consumption, combine smart-meter import and export with information from the solar inverter or monitoring platform.
Learn more in Solar Export Explained.
Home batteries
A home battery can change the grid-facing profile significantly.
When the battery charges from the grid, the smart meter sees increased import. When the battery discharges to supply the home, grid import falls or stops.
Possible patterns include:
- A concentrated block of overnight import
- Reduced imports during expensive tariff periods
- Very low evening grid demand
- Export during selected high-price periods
- Solar export beginning only after the battery is full
A high overnight reading does not necessarily mean electricity was immediately consumed by household appliances. Some of it may have been stored for later use.
Likewise, low grid import during the evening does not necessarily mean household demand was low. The battery may have been meeting a substantial load behind the meter.
This is why an import profile from a battery-equipped home should not be treated as a complete record of household electricity demand.
The future Home Battery Sizing Calculator will help turn consumption patterns into a more structured battery assessment.
Electric vehicles
An electric vehicle often produces one of the clearest patterns in half-hourly data: a sustained block of relatively high consumption.
The profile may help you establish:
- When charging started and finished
- The approximate amount of energy delivered
- Whether charging occurred during the intended tariff window
- Whether another major load operated at the same time
- How charging changed the home’s maximum demand
For example, a 7 kW charger running continuously would use approximately 3.5 kWh during each complete half-hour period. Charging power may be lower in practice because of the vehicle, charger, supply capacity or programmed controls.
A similar pattern could be produced by another large load, so the smart-meter data still cannot identify the charger with certainty. Comparing it with the charger’s own records provides confirmation.
Use the EV Charging Time & Cost Calculator to explore charging time, energy and tariff costs.
Heat pumps
Heat pumps tend to operate differently from traditional boilers. Rather than producing a short burst of high-temperature heat, a well-controlled heat pump may run at lower output for long periods.
Possible signs in the electricity data include:
- Sustained consumption across the day
- Greater demand during colder weather
- A separate domestic-hot-water cycle
- Changes corresponding with heating schedules or setback periods
- Occasional higher demand if auxiliary electrical heating operates
Half-hourly data can reveal when electricity was consumed, but it cannot calculate heat-pump efficiency by itself.
Calculating COP requires both:
- electrical energy supplied to the heat pump; and
- useful heat delivered by the system.
Smart-meter data may also include electricity used by everything else in the home. Dedicated heat-pump monitoring is therefore preferable when assessing detailed performance.
Read Heat Pumps in a Whole-Home Energy System for the wider relationship between heating, tariffs, solar panels, batteries and household demand.
Why smart-meter data is not a complete energy-flow picture
The smart meter provides the grid-facing part of the energy picture. Equipment behind the meter determines what happens inside the home.
A simplified whole-home energy balance is:
Grid import + solar generation + battery discharge = household consumption + battery charging + grid export
In practice, there are also inverter, battery and charging losses, but this simplified relationship shows why smart-meter data cannot answer every question independently.
| Question | Can smart-meter data answer it alone? |
|---|---|
| How much electricity entered from the grid? | Yes |
| When was electricity imported? | Yes, where half-hourly data is available |
| How much electricity was exported? | Usually, if export data is available |
| How much solar electricity was generated? | No |
| How much solar was consumed directly? | Not reliably |
| How much electricity charged the battery? | Not by itself |
| How much energy did the battery discharge? | Not by itself |
| Which appliance caused a peak? | No |
| When was the EV probably charging? | It may show a recognisable pattern |
| How efficiently is the heat pump operating? | No — heat-output information is also needed |
For the most complete picture, combine smart-meter information with data from the solar inverter, battery, EV charger and heat-pump monitoring system.
Explore the relationship further in Solar + Battery + EV: How They Work Together.
A five-step method for analysing your data
You do not need specialist software to learn something useful from half-hourly readings.
Collect a representative period
Begin with at least one normal week. Avoid holidays, unusual occupancy or periods when significant equipment was not operating normally. For investment or tariff decisions, analyse a much longer period where possible.
Establish the baseline
Find the repeated minimum demand during quiet overnight periods. Estimate its annual significance, but remember that heating and seasonal equipment can change the baseline throughout the year.
Mark recurring high-consumption periods
Look for consistent overnight charging, morning or evening peaks, hot-water cycles, prolonged winter demand, unexpected daytime consumption, and loads operating outside their intended tariff windows.
Compare the profile with equipment schedules
Check the smart-meter profile against EV charger history, battery schedules, solar generation, heat-pump controls, immersion-heater settings and time-of-use tariff periods. This helps distinguish deliberate demand from unexpected consumption.
Test what can realistically change
Not all electricity use should be shifted simply because another period is cheaper. Consider whether the equipment can be scheduled safely, the amount of energy that genuinely needs moving, battery charging and conversion losses, comfort and hot-water requirements, vehicle departure times, maximum import capacity, and whether an apparent saving depends on an export tariff.
The purpose is not merely to minimise one period’s grid consumption. It is to make the whole system work effectively.
Using half-hourly data to compare tariffs
Annual electricity consumption alone cannot reveal whether a time-of-use tariff will be suitable.
Two homes might each consume 5,000 kWh annually but have completely different profiles:
- One may use most electricity during the evening peak.
- Another may charge an EV and battery overnight.
- A third may import little electricity during summer because it has solar panels.
Applying each tariff’s prices to the home’s actual half-hourly consumption provides a much stronger comparison than assuming a standard household pattern.
A proper comparison should include:
- Import prices for every charging period
- Standing charges
- Export payments
- Battery losses
- Seasonal variation
- Any tariff eligibility requirements
- The household’s realistic ability to shift demand
Historical data is valuable, but it must be adjusted when future consumption will change. A household planning to install an EV or heat pump should not assume its old electricity profile will remain valid.
Using the data for battery planning
Half-hourly data can help identify:
- Evening grid demand
- Cheap-rate charging opportunities
- Solar export that might otherwise be stored
- The amount of consumption occurring outside solar-generation hours
- How frequently a proposed battery capacity might be used
There are two important traps.
First, smart-meter import from a solar-equipped home is not the same as total household demand because some electricity is already being supplied directly by the panels.
Second, smart-meter import from a battery-equipped home has already been reshaped by the existing battery. It may show when electricity crossed the meter rather than when the household ultimately consumed it.
Battery planning is strongest when grid data is combined with solar generation and existing device information.
How much data should you analyse?
- One day
- Helps explain the format.
- One week
- Can reveal repeated household routines.
- Several weeks
- Provide a more reliable normal-use pattern.
- Summer and winter
- Show how seasons affect generation and demand.
- Twelve months
- Provide the strongest basis for tariff and investment decisions.
The appropriate period depends on the decision being made.
Avoid sizing equipment or selecting a long-term tariff from one unusually sunny, cold or unoccupied week.
Future changes also matter. Adjust historical information if you expect to add:
- An electric vehicle
- A heat pump
- Electric water heating
- Solar panels
- A home battery
- Air conditioning
- A significant change in occupancy
Half-hourly data describes what happened in the past. Planning still requires a realistic view of what will happen next.
Missing, delayed or confusing data
Smart-meter information is not always complete or immediately available.
Missing half-hour periods
A missing reading should not automatically be treated as zero consumption. It may indicate:
- A temporary communication failure
- Delayed retrieval
- A supplier-platform problem
- A meter configuration issue
- Missing data after a supplier or tariff change
If several periods are absent, ask the supplier whether they are missing, delayed or estimated.
Delayed information
Supplier data is normally historical. Information shown by an IHD or Consumer Access Device may update much sooner than the graph in an online energy account.
A delay does not necessarily mean the smart meter has stopped working.
Import is available but export is missing
Export data may:
- appear in a separate account;
- be handled by a different supplier;
- require an export meter-point registration;
- be absent from the customer-facing portal even if readings are collected.
Ask the relevant export supplier where the half-hourly export information can be viewed or downloaded.
The times appear one hour out
Downloaded information may use Coordinated Universal Time, or UTC, rather than British local time.
This becomes particularly noticeable during British Summer Time. The days when the clocks change also contain a different number of local half-hour periods from a normal 24-hour day.
Check the file’s timestamp format before comparing it with appliance schedules or supplier prices.
The supplier graph does not match the bill
Differences can arise from:
- Estimated values
- Later corrections
- Different date boundaries
- Rounding
- UTC and local-time handling
- Billing periods that do not align with calendar days
Treat the bill as the supplier’s billing record and the half-hourly information as the detailed consumption history. Ask the supplier to investigate any material discrepancy.
Smart-meter data privacy
Smart meters record energy information for the property. They do not contain audio or video recordings, and they do not directly know which individual appliances are operating.
The meter itself does not need to store your name, bank details or account correspondence. However, consumption information held by a supplier can still be linked with a household energy account and should be treated as personal data.
Detailed patterns may reveal when a property is normally active or unoccupied. This is one reason access to the data is controlled.
In general:
- Suppliers and network organisations can use information for billing and other regulated purposes.
- Data-sharing choices depend on the applicable smart-meter arrangements.
- Marketing use requires appropriate permission.
- Third-party services require consumer authorisation.
- Customers can ask their supplier how frequently information is being collected and how it is used.
The Ofgem smart-meter guidance provides current information about domestic data-sharing choices.
What is Market-wide Half-Hourly Settlement?
Electricity suppliers must match the electricity purchased for their customers with the amount those customers consume.
Historically, much domestic electricity use was allocated across the day using estimated household profiles. Market-wide Half-Hourly Settlement is moving the industry towards using actual half-hourly consumption where available.
This creates a stronger connection between when electricity is consumed and the costs faced by suppliers. It is expected to support more:
- Time-of-use tariffs
- Flexible-energy rewards
- Automated charging services
- Battery products
- Demand-shifting schemes
The industry transition is continuing through 2027.
Half-hourly settlement does not mean every household will automatically pay a different price every 30 minutes. It changes the industry’s settlement process and creates better conditions for suppliers to offer flexible tariffs. Customers still need to choose a suitable retail tariff.
Frequently asked questions
Does a smart meter record electricity every half hour?
Smart electricity meters are capable of recording consumption in half-hour periods. Whether you can see or download those readings depends on the meter’s communication status, sharing settings and the services provided by your supplier.
Is half-hourly data the same as a live meter reading?
No. Half-hourly data records the energy consumed during completed 30-minute periods. Live or near-real-time monitoring provides much more frequent information about current electricity demand.
Can I download my half-hourly data?
Some suppliers allow customers to download CSV or spreadsheet files. Others only provide charts or require customers to request the information. Ask specifically whether import and export data can be downloaded.
Can the data identify individual appliances?
Not directly. The meter records total property consumption. Equipment can sometimes produce recognisable patterns, but another load could create a similar result.
Does the smart meter show total solar generation?
No. It can record electricity exported across the grid connection, but solar electricity used directly inside the home does not pass through the meter as export. Use the solar inverter or monitoring platform to obtain total generation.
Why are some readings missing?
Possible causes include communication interruptions, delayed data retrieval, supplier-platform problems or configuration changes. Do not assume a missing reading means zero consumption.
Can I use the data to choose a tariff?
Yes. Applying tariff rates to actual half-hourly consumption provides a much better comparison than annual consumption alone. Include standing charges, export payments and realistic future changes in demand.
Can half-hourly data size a home battery?
It is an important input, but it should not be used in isolation. Solar generation, export, future demand, battery losses, tariffs and the household’s objectives also need to be considered.
Bringing the information together
Half-hourly data transforms one electricity total into a detailed timeline. It can show when your home relies on the grid, when it exports surplus electricity and whether large flexible loads are operating at the intended times.
Its main limitation is equally important: the smart meter only sees electricity crossing the grid boundary.
Combine it with information from your solar inverter, battery, EV charger and heat-pump monitoring to understand the complete system. That combined picture can support better tariff selection, more effective controls and more realistic decisions about future equipment.