An NMI (National Metering Identifier) is the unique code that identifies an electricity connection point in Australia's National Electricity Market. A MIRN (Meter Installation Registration Number) is its equivalent for gas. Every site you buy energy for has one, and it's the reference that ties metered consumption, network tariffs, and billing back to a single connection.
For a single site, the NMI is a number on a bill you rarely think about. Across a portfolio of dozens or hundreds of connections, these identifiers are the primary key for everything: which meter belongs to which site, which tariff applies, and whether an invoice can be trusted. Get them wrong and consumption attaches to the wrong site, bills go unvalidated, and reports don't reconcile.
This guide covers what an NMI is, how it's structured, what a MIRN and a DPI are for gas, how the two identifiers differ, why they matter for commercial energy management, and where they tend to break at portfolio scale.
What Is an NMI (National Metering Identifier)?
An NMI is a unique identifier assigned to every electricity connection point, or grid connection point, in the National Electricity Market. It's allocated by the local distributor, the business that owns the poles and wires in your area, and stored centrally in AEMO's Market Settlement and Transfer Solution (MSATS), the registry that tracks every connection in the NEM. The NMI identifies the connection point, not the physical meter. One NMI can have several meters or registers sitting behind it.
The base NMI is ten characters, usually shown on a bill with an eleventh digit on the end. The characters are generally numeric, but a valid NMI can contain letters in limited circumstances. Two parts are worth knowing.
The first characters identify the network. Every distributor is allocated its own block of NMIs, so the opening characters tell you which distribution region a connection sits in, and therefore which set of network tariffs applies to it.
The last digit is a checksum. The eleventh character is a check digit calculated from the other ten. Checking it helps catch data-entry mistakes. It doesn't replace matching the identifier to the correct supply address and connection.
You'll find the NMI on your electricity bill, usually under the supply or connection details rather than next to the charges. It stays with the connection, not the retailer, so it doesn't change when you switch energy providers.
What Is a MIRN, and What's a DPI?
A MIRN (Meter Installation Registration Number, sometimes called a Meter Installation Reference Number) is the gas equivalent of an NMI. It uniquely identifies a gas connection point, and it's allocated by the gas distributor for the network the site sits in. The naming isn't consistent across the country, which is the part that catches people out.
MIRN is the term used in Victoria, Queensland, and South Australia.
DPI (Delivery Point Identifier) is the same identifier under a different name, used in New South Wales and the ACT.
A MIRN or DPI is a ten-character identifier that starts with 5, sometimes shown with an eleventh checksum digit. The first two digits map to the state: 53 for Victoria, 54 for Queensland, 55 for South Australia, and 52 for New South Wales and the ACT. Like the NMI, it identifies the delivery point rather than the meter hardware, and it stays with the connection when you change retailer.
How Do NMI and MIRN Differ?
They do the same job for different fuels. Four distinctions matter in practice.
Fuel. The NMI identifies an electricity connection. The MIRN or DPI identifies a gas connection. A site with both power and gas has one of each, and they share no numbering.
Format. An NMI is ten characters and usually numeric. A MIRN or DPI starts with 5. That difference alone is often enough to tell which identifier you're looking at.
Terminology. Electricity is consistent nationwide: it's always an NMI. Gas isn't. The same identifier is a MIRN in most states and a DPI in New South Wales and the ACT, which trips up anyone consolidating gas data across a national portfolio.
Who issues it. Both are allocated by the relevant distributor and stay attached to the connection, independent of which retailer bills it. Switching providers never changes the identifier.
Why Do Meter Identifiers Matter for Commercial Energy?
For one site, the NMI is trivia. Across a portfolio, it's infrastructure. Four reasons it matters.
It's the primary key for consumption data. Every meter read and every interval of consumption is tagged to a NMI or MIRN. Data arrives keyed to the identifier, and matching it to the right site is the first step in making it useful.
It's how invoices get validated. Validating an invoice means tying the billed charges back to the metered consumption for a specific connection. Without a clean NMI-to-site mapping, you can't tell whether a bill even belongs to the site it's charged to, let alone whether the charges are right.
It's the backbone of a procurement tender. A credible energy tender needs a complete register of every connection with its NMI or MIRN, its historical consumption, and its network tariff. Retailers price off the NMI list. Miss a connection and the contract that comes back doesn't cover the whole portfolio.
It's how reporting rolls up. NABERS ratings, Scope 2 emissions, and site-level benchmarking all aggregate consumption by connection. If two sites share a NMI in the data, or one site's NMI is missing, the numbers don't reconcile against the bills.
Where Meter Identifiers Cause Problems at Scale
Most identifier problems don't show up until a portfolio grows past what a spreadsheet can track. A few recur.
Missing or duplicated identifiers. A connection with no NMI recorded, or the same NMI entered twice against different sites, quietly corrupts every total built on top of it.
Gas terminology drift. The MIRN-versus-DPI split means the same field is labelled differently across states, so a national dataset assembled by hand ends up with gas connections in two naming conventions that don't line up.
Embedded networks and child NMIs. Shopping centres, office towers, and industrial estates often sit behind a parent connection with child NMIs for individual tenancies. Mapping those correctly matters for tenant billing and for multi-site reporting, and it's easy to get wrong by hand.
The common thread is manual handling. A NMI copied from a PDF into a spreadsheet is a single keystroke away from pointing at the wrong connection, which is exactly why the checksum digit exists. Identifiers break where people retype them.
How Utilified Uses NMI and MIRN as a Data Spine
Utilified's Utility Management System (UMS) organises companies, sites, connections and registers in one unified hierarchy. NMI and MIRN records help link electricity and gas consumption, invoices and recorded contracts to the right connection. Water and waste can sit alongside them in the portfolio using the relevant service identifiers. Available source feeds and validation coverage depend on the utility, account configuration and supporting data.
UMS supports invoice validation and exception review against recorded rates and, where supported, interval data. Joule helps authorised users investigate portfolio questions using the available platform tools and permissions. Keeping connection identifiers accurate gives these workflows a reliable starting point for utility decisions.
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Frequently Asked Questions
What is an NMI?
An NMI (National Metering Identifier) is the unique code that identifies an electricity connection point in Australia's National Electricity Market. It's ten characters, sometimes shown with an eleventh checksum digit, allocated by the local distributor and stored in AEMO's MSATS registry. It identifies the connection, not the meter, and stays the same when you switch retailer.
What is a MIRN?
A MIRN (Meter Installation Registration Number) is the gas equivalent of an NMI. It uniquely identifies a gas connection point, is a ten-character identifier starting with 5 (sometimes shown with an eleventh checksum digit), and is allocated by the gas distributor. The term is used in Victoria, Queensland, and South Australia.
What's the difference between a MIRN and a DPI?
None in function. A MIRN and a DPI (Delivery Point Identifier) are the same gas connection identifier under different names. MIRN is used in Victoria, Queensland, and South Australia. DPI is the term used in New South Wales and the ACT.
Where do I find my NMI or MIRN?
The NMI is on your electricity bill, usually under the supply or connection details. The MIRN or DPI is on your gas bill, often on the second page. Both stay with the connection rather than the retailer, so neither changes when you switch providers.
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