How to read an AEMO NEM12 interval metering file: what each record type means, how to read quality flags and the timezone trap that quietly shifts your readings.
A NEM12 file is the standard format AEMO defines for sharing interval electricity metering data in the National Electricity Market. It follows AEMO’s Meter Data File Format (MDFF) specification. Your electricity retailer or metering data provider produces it, and it records the energy a site consumed or exported in each metering interval across a date range.
NMI = National Metering Identifier, the unique ID for a connection point.
A NEM12 file is a flat CSV built from numbered record types. Reading them in order tells you whose meter it is, at what resolution, then the readings themselves:
The 200 record sets the interval length, usually 5, 15 or 30 minutes. A 30-minute file therefore carries 48 readings per 300 row, a 5-minute file carries 288. Every reading carries a quality flag that tells you how trustworthy it is:
For an audit-defensible Scope 2 calculation, knowing how much of a period is actual versus substituted matters. A month that is mostly substituted data is weaker evidence than one that is fully metered.
NEM12 timestamps are local time on a fixed offset with no daylight saving. The eastern states use AEST (UTC+10) all year and Western Australia uses AWST (UTC+8). If you load a file and convert it assuming the local clock observed daylight saving, every interval shifts by an hour for the months daylight saving is in effect, which quietly misaligns the data against time-of-use periods and time-matched carbon factors.
What is a NEM12 file?
A NEM12 file is the standard format AEMO defines for sharing interval electricity metering data in the National Electricity Market. It follows the Meter Data File Format (MDFF) specification and records how much energy a site consumed or exported in each metering interval across a date range.
What is the difference between NEM12 and NEM13?
NEM12 carries interval data, with a reading for every 5, 15 or 30-minute interval. NEM13 carries accumulated (basic) metering data, typically a single total between manual reads. Time-matched Scope 2 and load analysis need NEM12 interval data.
Where do I get my NEM12 file?
From your electricity retailer or your metering data provider (MDP). Most retailers can email a NEM12 export for a billing period on request, and larger sites often receive them as part of regular data services.
Why do my NEM12 timestamps look an hour off?
NEM12 timestamps are local time on a fixed offset with no daylight saving. The eastern states use AEST (UTC+10) all year and Western Australia uses AWST (UTC+8). Converting the readings as if they observed daylight saving shifts every interval by an hour for part of the year.
gridIQ reads NEM12 natively. Drop the file your metering provider sent and gridIQ maps each NMI to its market region and returns dual-method Scope 2 with a DCCEEW factor audit trail.
Free Scope 2 calculator →Scope 2 guide