How to Interpret Your Smart Meter Data

Register codes E1, B1, E2, Q1 and K1 explained for solar and consumption analysis

Last Updated: 2026-08-05

Key Takeaways

• Your file holds one block of Interval Data for each Meter Register, not one usage figure per day.
• E1 is a mains grid import register. Where a meter has more than one E register, E1 is almost always the Main/General register.
• B1 is always Solar Export in kWh — the register for PVOutput generation uploads and Feed-in Tariff checks.
• E2 is a second mains import register, typically a controlled load such as hot water. Your solar cannot supply a load on E2.
• Q1 and K1 measure Reactive Energy in kVARh. Residential and small business readers can ignore both registers.
• The Register Code (also called the NMI Suffix) appears in the NMIConfiguration field of each 200 record in a NEM12 file.
• Each DNSP labels the same Smart Meter Data in its own way. Some portals use the raw codes, and other portals use plain-English column names.

What Your Downloaded Smart Meter Data File Contains

Your download from the DNSP portal holds more than one stream of readings. The file records a separate block of Interval Data for each Meter Register on your connection. Every block carries its own Register Code.

• Mains import: the electricity you drew from the grid, recorded in kWh.
• Solar Export: the electricity your solar system sent to the grid, recorded in kWh.
• Controlled load import: a separately switched circuit such as hot water, recorded in kWh, present on some connections only.
• Reactive Energy: a technical measurement in kVARh, present in some files, and not used for solar analysis.

Why Your Smart Meter Data File Looks Confusing

AEMO defines the NEM12 CSV Format and uses it as one of its internal data exchange formats. AEMO supplies NEM12 CSV because the format is well defined, available, and carries interval data. AEMO does not supply it because a homeowner or an energy professional finds it easy to read.

• Cryptic codes: the Register Code is a two-character code such as E1 or B1, not a plain-English column name.
• Mixed rows: one NEM12 file holds several row types, so the file does not open as a clean table.
• Portal variation: each DNSP implements the format in its own way, so column labels vary between portals.

This guide explains the register codes. For the record structure of the format itself, see our technical guide on how to understand the NEM12 CSV format. If you have not downloaded a file yet, start with how to download your smart meter data.

What Is a Meter Register on a Smart Meter?

A smart meter is not a single counter. The meter measures several energy quantities at the same time. Each measured quantity is a Meter Register, also called a channel.

AEMO identifies each register with a two-character NMI Suffix. The 200 record at the top of each meter block lists every suffix in a field called NMIConfiguration. For example, the value "E1B1E2" tells you that the file carries three registers:

• E1: mains grid import.
• B1: solar export.
• E2: a second mains grid import register, typically a controlled load.

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Register Codes for Mains Import and Solar Export

These register codes matter for consumption analysis and solar analysis at homes and small businesses.

B1 is always Solar Export. 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.

Why the Main/General Register Matters for Solar

Solar generation on site can only supply demand from loads connected to the Main/General register. Loads on any other register cannot use your solar electricity.

• A controlled load on E2 imports at midday. The circuit draws from the grid while your solar system generates, because your solar cannot reach that circuit.
• A controlled load never appears on B1. B1 records export only, so a hot water circuit stays on a secondary import register.
• Daytime import on E2 is not a fault. Check the register code before you treat midday import as solar under-performance.

Mains Import, Solar Export and Total Demand

• Mains import: the E1 readings, plus E2 or E3 where the file carries them. This is the electricity you bought from the grid.
• Solar Export: the B1 readings. This is the solar electricity you sent to the grid rather than used on site.
• Total demand: mains import plus the solar electricity you used on site. Most NEM12 files do not record total solar generation, so you cannot calculate total demand from E1 and B1 alone.

Reactive Energy Register Codes — Q1 and K1

Some NEM12 files also carry registers labelled Q1 and K1. These registers look like extra consumption or generation channels. They measure something different.

Q1 and K1 measure Reactive Energy in kVARh, not in kWh. Reactive energy is a property of AC circuits, related to the phase between voltage and current. Meters record it on connections with inductive loads and solar inverters.

Australian residential electricity tariffs do not include reactive energy charges. Solar design tools and monitoring portals do not use Q1 or K1. Reactive energy registers matter to large commercial and industrial customers whose tariffs include power factor penalties.

Which Register Code Do You Need?

The register you select depends on the task in front of you.

PVOutput, OpenSolar, SolarPlus, SolarProof, and Pylon accept NEM12 CSV. None of these tools requires the NEM12 CSV Format specifically. Each tool states the formats it takes, so read that list before you convert a file. For the upload steps for each solar design tool, see our guide on how to import NEM12 CSV into solar design tools.

Get an Instant Explanation of Your NEM12 CSV File

Rather than reading the register codes by hand, upload your CSV file to our free Smart Meter Data CSV File Explainer. The tool does the following automatically:

• Detects the DNSP source and the format of your file
• Lists every register found — E1, B1, E2, Q1, K1, and others
• States in plain English what each register measures, and its unit (kWh or kVARh)
• Flags which registers suit solar analysis and consumption analysis, and which registers you can ignore
• States which channel to select for an upload to PVOutput, OpenSolar, or SolarPlus

Our free online tools require no payment and no sign-up. The tools never retain your data and never share it with a third party.

How DNSP Portals Label the Same Data Differently

Not every DNSP presents Smart Meter Data in the standard NEM12 CSV Format with NMI Suffix codes. Some portals export a simplified CSV file with descriptive column headers. The same E1 and B1 readings can appear under different labels.

Portal names and column labels change from time to time. Read the file you downloaded rather than the table alone. If a tool rejects your file, our free Smart Meter Data NEM12 CSV File Validator can check it.

Free Online Tools for Smart Meter Data in NEM12 CSV Format

• NEM12 Smart Meter Data Analyzer — Visualise and summarise your E1 and B1 interval data with charts and tables
• All Free Online Tools — Browse the full set of free energy data tools

Try our NEM12 Smart Meter Data Analyzer Tool

Our free online tools require no payment and no sign-up. The tools never retain your data and never share it with a third party.

Frequently Asked Questions

• What is a Register Code in a NEM12 file? A Register Code, also called the NMI Suffix or the Meter Register, is a two-character code that labels one data stream from your smart meter. Examples include E1, B1, E2, Q1, and K1.
• Where do Register Codes appear in a NEM12 CSV file? They appear in the NMIConfiguration field of the 200 record that opens each meter block. They also appear again on each interval data row, so every row ties back to one register.
• Which Register Code is my Solar Export? B1 is always Solar Export — the electricity generated on site and fed back to the grid, measured in kWh.
• Is E1 the same as my total household consumption? No. E1 is mains grid import only, so a home with solar also consumes solar electricity that never appears on E1.
• Can I calculate total demand from E1 and B1? Not exactly. Total demand is mains import plus the solar electricity used on site, and most NEM12 files do not record total solar generation.
• What does E3 mean in a NEM12 file? E3 is a further mains grid import register. E1, E2, and E3 are always mains grid import registers, never export registers.
• Why does my hot water circuit on a controlled load import at midday? Solar generation can only supply loads connected to the Main/General register, so a controlled load on E2 draws from the grid while your solar system generates.
• Can a controlled load appear on the B1 register? No. A controlled load or dedicated circuit appears on a secondary import register, typically E2, because B1 records export only.
• Which register matches the "Generated" field in PVOutput? B1. The PVOutput Generated field takes solar export to the grid in kWh, which is what the B1 Meter Register records.
• Do PVOutput, OpenSolar and SolarPlus require a NEM12 CSV file? No. PVOutput, OpenSolar, SolarPlus, SolarProof, and Pylon accept NEM12 CSV, but none of them requires that format specifically.
• Can I check my Feed-in Tariff credit with B1 data? Yes. Sum the B1 kWh readings for the billing period, then multiply the total by your retailer FiT rate in cents per kWh.
• Why do my Q1 and K1 registers have values if I never use Reactive Energy? Your premises does draw and push reactive energy, because motors, transformers, and inverters do so. Australian residential tariffs do not charge for it.
• What is the difference between kWh and kVARh? kWh is the unit of electrical energy recorded on the E and B registers. kVARh is the unit of Reactive Energy recorded on Q1 and K1, and the two units are not interchangeable.
• My file shows "Consumption" and "Generation" instead of E1 and B1. Which is which? Consumption maps to E1, the mains grid import, and Generation maps to B1, the Solar Export. Some DNSP portals simplify the export rather than use the raw NMI Suffix codes.
• What is a DNSP, and is it the same as my Electricity Retailer? A DNSP owns the poles, the wires, and your meter, and it supplies your Smart Meter Data. Your Electricity Retailer sells you the electricity and issues the bill.
• Do I need the E2 register if my hot water is on the main circuit? No. E2 appears only where a controlled load tariff exists, and hot water on the main supply already sits inside the E1 readings.

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Glossary

AEMO

Australian Energy Market Operator — the body that administers the National Electricity Market and defines and maintains the NEM12 specification.

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.

Channel

See NMI Suffix.

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'.

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.

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.

Feed-in Tariff

The rate a retailer credits you for electricity your system exports to the grid, usually counted per kilowatt hour.

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.

K1

In the NEM12 Format, the NMI Suffix for Reactive Energy Export (kVARh). Appears most often in larger commercial but also in some residential NEM12 files but is never relevant for solar analysis or consumption analysis. See also: Reactive Energy, kVARh, NEM12, NMI.

kVARh

Kilovolt-Ampere Reactive Hour — the unit of Reactive Energy. Not the same as kWh. Reactive energy (kVARh) is measured by Q1 and K1 registers. It does not appear on residential electricity bills and is not used by solar analysis tools. See also: Reactive Energy.

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.

Meter Register

See NMI Suffix.

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.

NMIConfiguration

The field on a NEM12 200 record listing every NMI Suffix present for the meter (e.g. "E1B1") — the quickest way to see which channels a file carries. See also: NMI, NMI Suffix.

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.

Q1

In the NEM12 Format, the NMI Suffix for Reactive Energy Import (kVARh). Appears in some residential NEM12 files but is never relevant for solar analysis or consumption analysis. See also: Reactive Energy, kVARh, NEM12, NMI.

Quality Flag

In the NEM12 Format, a single-letter code on each interval reading showing how the value was obtained — e.g. A (Actual), E (Estimated), S (Substituted), F (Final Substitute). See also: NEM12.

Reactive Energy

A property of AC electrical circuits related to the phase relationship between voltage and current. Measured in kVARh (not kWh). Recorded in Q1 (import) and K1 (export) registers. Not charged on residential electricity bills in Australia; not used by solar design tools or energy monitoring portals. See also: kVARh.

Register Code

See NMI Suffix.

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.

Solar Export Limit

The maximum rate (in kW) at which your DNSP permits your solar system to export electricity to the Mains Grid. In Victoria, the standard limit for single-phase connections is 5 kW. Export above this limit is prevented by your inverter. See also: DNSP, kW.

Solar Feed-in Tariff (FiT)

The credit paid (in cents per kWh) by your Electricity Retailer for solar electricity you export to the grid (B1 Meter Register). In Victoria, a minimum rate was historically set annually by the Essential Services Commission (ESC). However, since July 2025, the ESC no longer sets a minimum, and Electricity Retailers are free to pay a Market Rate.

Time-of-Use (TOU) Tariff

A tariff with different prices at different times of day or days of the week (Peak, Shoulder, Off-Peak).

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