How to Visualize NEM12 Data with Charts

Choose the right chart type and build a daily energy profile in your spreadsheet

Last Updated: 2026-08-05

Key Takeaways

To chart smart meter data well, first average your 48 half-hourly intervals into one daily energy profile. Average the intervals. Do not sum them.
Match the chart to the question. A column chart compares totals, a line chart traces a trend, and a stepped area chart holds each reading flat across its own window.
Chart import (E1) and solar export (B1) together to see the solar supply window and the self-consumption gap.
A day of week pattern view sets an average weekday against an average weekend, and often shows a load-shifting opportunity.
An energy use heatmap with hour against date shows anomalies and seasonal creep at a glance.
You can visualize NEM12 data in a spreadsheet, or in a browser-based tool that reads the file directly.

Step 1 — Build a Daily Energy Profile Before You Chart

A NEM12 CSV holds 48 half-hourly interval readings per register per day. At that resolution the raw numbers hide the pattern. The first task, when you visualize NEM12 data, is to collapse the intervals into one average day.

Each interval reading is the energy used inside a fixed 30-minute window. Average each time slot across every day in the sample. A sum gives a total, and an average gives a shape you can compare.

Keep each register separate. Average E1 (import), E2 (any controlled load), and B1 (solar export) on their own. Never add an import register to an export register.
Average by time slot. The mean of every 09:00 to 09:30 reading becomes one point in the profile.
Repeat for all 48 slots. The 48 averages together form the daily energy profile.
Use a wide-format layout. One column per time interval makes the load profile straightforward to chart.

This guide starts from data that already sits in tabular form. To get the file into a spreadsheet first, see our guide to opening NEM12 data in a spreadsheet. To build the averages with a pivot table, see our guide to analysing NEM12 data in a spreadsheet.

The record layout behind the NEM12 CSV Format is a separate subject, and our guide to understanding the NEM12 CSV Format covers it. You can follow along with this sample NEM12 CSV (E1 and B1) from a real Powercor export. The same data is also published as a Google Sheet of the same sample data.

Step 2 — Match the Chart Type to Your Question

No single chart type is best for smart meter data. The right chart depends on the question you ask. Choose the chart type that answers your question, rather than the default your spreadsheet offers first.

The question you are asking	Chart type that suits it
How does total use compare across months or seasons?	Column chart
How does the level rise and fall through the day?	Line chart or stepped area chart
How much energy sits under the curve overall?	Area chart
What does a half-hourly shape really look like?	Stepped area chart
When do import and export overlap during the day?	Column or stepped area chart, two series

Column chart: compares discrete totals, because bar heights are easy to read against each other.
Line chart: traces the trend and shows how the level rises and falls through the day.
Area chart: shades the region under the line, so a winter day laid over a spring day shows the difference in cumulative kWh.
Stepped area chart: holds each reading flat across its own 30-minute window.

Column chart: household with 3 mains import registers (E1, E2, E3) and no solar - average daily mains import per register for each season

The column chart above compares average daily import per register for each season. A season-by-season comparison is a totals question, so a column chart fits it.

Step 3 — Use a Stepped Area Chart for Half-Hourly Data

Interval data is constant inside each window. A reading labelled 18:00 to 18:30 is the total energy for that whole slot, not a level at one instant. A smooth line chart draws a diagonal between two points, which implies a glide the meter never recorded.

A line chart joins the readings with diagonals. Use it for a smoothed daily-average profile, where only the broad trend matters.
A stepped area chart holds each value flat, then steps to the next value. Use it when the interval structure matters, such as a sharp switch-on event, a controlled-load cycle, or the start of solar export.

Stepped area chart: household with 1 mains import register (E1) and solar export (B1) - average daily import and solar export per month

Every 30-minute window then reads as a flat-topped plateau. The chart matches the way the meter measured the energy.

Step 4 — Chart Import and Export Together (E1 and B1)

A chart of grid import beside solar export is one of the most useful views for a solar home. E1 against B1 shows the solar supply window, and the demand the solar did not meet.

Column chart: household with 1 mains import register (E1) and solar export (B1) - average daily import and solar export per month

B1 is always solar export — the electricity your panels sent back to the grid.
E1, E2, and E3 are always mains-grid import registers. Where a meter has more than one E-register, E1 is almost always the Main/General register.
Self-consumption is the gap between generation and B1 export. It is the solar you used on site.

From time to time a NEM12 file appears to show another register as the Main/General register. Treat such a file as suspect, and verify it before you rely on it. On-site solar can only supply demand from loads connected to the Main/General register.

A controlled load, such as a hot water service on a dedicated circuit, therefore sits on a secondary import register, typically E2, and never on B1. For a full breakdown of each register code, see our guide to interpreting your smart meter data.

Only the E1 bars fall when solar is added. That is the register solar can offset.
A controlled-load register such as E2 stays flat with or without solar, because the grid alone feeds it.

Column chart: household with 3 mains import registers (E1, E2, E3) and no solar - average daily mains import per register for each month

Chart each register as its own series to make this visible. Our guide to analysing NEM12 data in a spreadsheet covers the separation of the registers.

Stepped area chart: household with 3 mains import registers (E1, E2, E3) and no solar - average daily mains import per register for each month

A monthly column chart with three registers can become crowded. The same three registers read as separate bands on a stepped area chart.

Step 5 — Reveal the Day-of-Week Pattern

Many households assume that every day looks the same. A day of week pattern often tells a different story. Chart an average weekday profile against an average weekend profile, as two lines on one axis.

Weekday shape: a sharper morning peak near 08:00, a quiet middle of the day, then a strong evening peak from about 16:00 to 22:00.
Weekend shape: a later and gentler start that lifts through the day, without the sharp weekday morning spike.

A quiet weekday middle of the day, beside a midday solar peak, points to a load-shifting opportunity. Run the dishwasher inside the solar window, or charge a vehicle there. A line chart overlay shows the difference before you commit to a time-of-use tariff decision.

Step 6 — Spot Anomalies with an Energy Use Heatmap

An energy use heatmap shows a whole month at once. Put hours of the day on one axis and dates on the other axis. Colour each cell by its interval value.

Build it with conditional formatting. Apply a colour scale across the grid. The menu wording for conditional formatting varies by application and by version.
Read the overnight band. A steady dark strip in the small hours is your baseload. A single bright cell is an anomaly worth investigating.
Watch for seasonal creep. Bands that intensify week on week signal a rising heating or cooling load.

A heatmap needs no chart wizard, and it exposes day-of-week shifts and seasonal shifts quickly.

Step 7 — Chart Smart Meter Data in the Browser Instead

You can chart smart meter data in the browser instead of building formulas. That path is faster when you want to see the pattern before a load-shifting decision or a battery-sizing decision.

Try our NEM12 Solar-Export Battery-Sizer Tool

Loads your NEM12 CSV as it is. No manual pivot table or wide-format reshape is required.
Groups by hour, day, weekday against weekend, month, or season. The tool switches between column, line, and stepped area charts.
Keeps each register distinct, so E1, E2, and B1 stay readable on one chart.

Column chart: household with 1 mains import register (E1) and solar export (B1) - average daily import and solar export per season

The free NEM12 Smart Meter Data Analyzer runs entirely in your browser. You can browse the wider set at our online tools collection. Test either approach with the same sample NEM12 CSV before you trust it with your own data.

Try our NEM12 Smart Meter Data Analyzer Tool

Frequently Asked Questions

What is a daily energy profile? It is the average shape of one day of electricity use, built by averaging each half-hourly interval across every day in your sample.
Should I sum or average my intervals to build a daily energy profile? Average them. A sum gives a total, and an average of each time slot gives the comparable shape you want to chart.
What data layout suits a daily energy profile chart? A wide-format layout, with one column per half-hourly interval and one row per day, charts all 48 points as a single series.
Which chart type is best to visualize NEM12 data? No single type is best. Use a column chart for totals, a line chart for trend, and a stepped area chart for half-hourly structure.
When should I use a column chart for smart meter data? Use a column chart to compare discrete totals, such as average daily use across months or seasons, where bar heights read clearly against each other.
What does an area chart show that a line chart does not? An area chart shades the region under the line, which emphasises cumulative volume rather than the exact level at one moment.
Why does a stepped area chart suit interval data? Each reading is constant inside its 30-minute window, so a stepped area chart holds it flat and then steps to the next value.
How many readings are in one day of NEM12 data? A standard NEM12 CSV records 48 half-hourly interval readings per register per day.
What does a chart of E1 against B1 show? It shows the solar supply window and the self-consumption gap, because it puts grid import beside solar export across the same day.
Can solar power supply a controlled load on E2? No. On-site solar can only supply demand from loads on the Main/General register, so a controlled load on a secondary register such as E2 stays on grid supply.
What is a day of week pattern in energy data? It is the difference between weekday and weekend shapes, typically a sharp weekday morning peak against a later and gentler weekend rise.
What is an energy use heatmap? It is a grid with hour of day on one axis and date on the other axis, where colour intensity encodes the interval value.
How do I build an energy use heatmap in a spreadsheet? Apply a conditional-formatting colour scale over the grid of values. The menu wording varies by application and by version.
Why does a monthly chart with three registers become hard to read? Three series of columns crowd each month, so a stepped area chart separates the same registers into readable bands.
Do I need a spreadsheet to chart smart meter data? No. A browser-based tool such as the NEM12 Smart Meter Data Analyzer charts a NEM12 CSV directly, without formulas.
Where does my interval data come from? It is smart meter data recorded against your NMI, and you download it from your DNSP portal or from your electricity retailer portal.
Who defines the NEM12 CSV Format? AEMO defines the NEM12 CSV Format, and market participants such as your DNSP produce files to that specification.

Try our NEM12 Smart Meter Data Analyzer Tool

Glossary

AEMO: Australian Energy Market Operator — the body that administers the National Electricity Market and defines and maintains the NEM12 specification.
Area Chart: A chart that fills the region between a line and the axis, emphasising the cumulative volume (the area) rather than the precise level at each point.
B1: In the NEM12 Format, the Meter Register code for Solar Export — electricity generated on site and fed back to the grid, typically measured in kWh.
Baseload: The continuous background electricity draw. In a Residential Home, when active appliances are off, estimated from the overnight minimum.
Check Digit: The 11th digit of a full NMI — calculated from the first ten digits to detect transcription errors; some DNSP portals require it. Also called a 'Checksum'.
Column Chart: A chart that represents each value as a vertical bar, well suited to comparing discrete totals such as average daily use across months or seasons.
Controlled Load: A separately metered circuit controlled by a signal from the DNSP. These circuits typically contain a single specific appliance or type of appliance - eg. an Electric Hot Water Service (and historically Air-Conditioners or Electric Slab Heating). They are typically billed at a discounted rate and often run only during off-peak hours. They appear on a separate Meter Register on an Electricity Bill. See also: Dedicated Circuit.
CSV: Comma-Separated Values — a plain text file in which each row is a record and fields are separated by commas.
Daily Energy Profile: The average shape of a single day's electricity use or generation, produced by averaging each time interval across many days. A daily-grained load profile. See also: Load Profile.
Day of Week Pattern: The characteristic difference in an electricity profile between weekdays and weekends, reflecting occupancy and household routine.
Dedicated Circuit: The physical wiring and breaker serving a Controlled Load device, isolated so the DNSP can independently control supply. See also: Controlled Load.
DNSP: Distribution Network Service Provider - the company that owns and operates the physical poles and wires of the local electricity network, and usually provides the smart meter data portal. Not the same as your Electricity Retailer. See also: Electricity Retailer.
E1: In the NEM12 Format, the Meter Register code (or NMI Suffix) for the sole/main/primary mains grid import channel — electricity drawn from the network. Where there is No (Solar) Generation on site, this is the Total Consumption. Typically measured in kWh.
E2: In the NEM12 Format, the Meter Register code (or NMI Suffix) for a secondary mains grid import channel — typically controlled-load or off-peak consumption such as dedicated hot water. Present only where that tariff exists.
Electricity Retailer: The company that sells electricity to the consumer, issues the bill, and manages the account. Not the same as your DNSP (Distribution Network Service Provider) which owns and operates the network. See also: DNSP.
Energy Use Heatmap: A grid visualisation with the hour of day on one axis and the date on the other, where colour intensity encodes energy use — useful for spotting anomalies at a glance.
Half-Hourly Data: Interval data recorded every 30 minutes — 48 readings per register per day.
Interval Data: Energy readings recorded at fixed time steps — typically every 30 minutes (but sometimes 5 or 15 minutes on newer meters) rather than as a single billing total. This allows charging different Tariffs at different times of day or days of the week. See also: Time-of-Use (TOU) Tariff.
kW: KiloWatt — the standard unit of (Electrical) Power: 1,000 Watts of Power used continuously for one hour is equivalent to 1000 Watt-Hours or 1 KiloWatt-Hour of Energy. Power is not an Amount of Energy but a Rate of Energy Transfer. See also: kWh.
kWh: KiloWatt-Hour — the standard unit of (Electrical) Energy: 1,000 Watts of Power used continuously for one hour is equivalent to 1000 Watt-Hours or 1 KiloWatt-Hour. NEM12 CSV records Electricity Use in kWh. See also: kW.
Line Chart: A chart that joins successive values with straight segments to trace a trend over time; it implies continuous change between the plotted points.
Load Profile: The pattern of a site's electricity use over time, derived from its interval data. The granularity or resolution of the Profile is the Interval Length (eg. 30 Minutes, Hours), and is typically based on averages for a longer period (eg. Months, Seasons).
NEM: The Australian National Electricity Market — the interconnected electricity grid covering Queensland, New South Wales, Victoria, South Australia, Tasmania and the ACT. Western Australia and the Northern Territory operate separate grids.
NEM12: The AEMO file format (version 12) for exchanging Interval Data from Smart Meters across the Australian National Electricity Market (NEM). NEM12 Format records the Amount of Energy per Time Interval in kWh. And also other types of data, using specific types of labelled rows or records (100, 200, 300, 400, 900) to record different types of data. This makes it a 'Semi-Structured' 'Non-Tabular' Format. See also: AEMO, NEM, kWh, Semi-Structured, Non-Tabular.
NEM12 CSV: A NEM12 File stored as comma-separated values — the form most DNSP and retailer portals distribute. See also: NEM12, CSV.
NMI: National Metering Identifier — the unique 10-digit identifier for an electricity connection point (11 with the Check Digit), permanent to the property. Note that the electricity connection point identified by the NMI, typically has multiple NMI Suffixes, and can have multiple Physical Meters. See also: Check Digit, NMI Suffix.
NMI Suffix: In the NEM12 Format, the short two-character code (E1, E2, E3, B1, B2, Q1, K1) identifying a specific Meter Register for recording electricity flows on the mains electricity connection identified by that NMI — also called the Meter Register or Register Code. See also: NMI, NEM12.
Non-Tabular: Data that does not fit a single consistent grid — in NEM12's case because of its semi-structure, hierarchy and mixed-record layout.
Self-Consumption: The share of the electricity generated by your own solar panels that your household uses on site, rather than exporting it to the grid.
Semi-Structured: A data format that follows strict syntactic rules (e.g. comma separation, defined record codes) but does not enforce a consistent column schema across all rows. NEM12 is a Semi-Structured Format. See also: NEM12.
Smart Meter Data: Electricity import and export readings recorded by a digital interval meter at regular intervals. In Australia, typically supplied in NEM12 CSV Format with 30 Minute Intervals. See also: NEM12 CSV.
Stepped Area Chart: An area chart that holds each value flat across its interval and steps to the next, honestly representing constant-within-interval meter readings rather than smoothing between them.
Time-of-Use (TOU) Tariff: A tariff with different prices at different times of day or days of the week (Peak, Shoulder, Off-Peak).
Wide Format: A table shape with one row per day per Meter Register and one column per Time Interval — good for charting a Load Profile. See also: Load Profile.

Try our NEM12 Smart Meter Data Analyzer Tool