A large inverter-based load is a facility, such as a data centre or hydrogen electrolyser, that draws its power through power electronics rather than motors or resistive equipment. AEMO wants performance standards for these loads because many of them can trip together during a grid fault. The AEMC's March 2026 draft rule set a 30 MW threshold with three size tiers; the final rule is still to be confirmed.
Where the Rule Change Stands
ERC0394 status at 6 November 2026
- Rule change: Improving the NEM access standards, Package 2 (ERC0394)
- Draft determination and draft rule published 12 March 2026
- Submissions on the draft closed 7 May 2026
- Final determination deadline extended, with publication targeted for 29 October 2026
- No final determination had been published as at 6 November 2026
- Check the AEMC project page for the final rule before relying on any threshold
The AEMC extended its timeline after submissions on the draft raised complex issues, including where the threshold should sit. Treat this article as a guide to what the draft proposes; the engineering logic will hold, but the numbers might move.
Why Loads Now Need Performance Standards
For decades the National Electricity Rules treated load as passive. Generators had to ride through faults and provide models; loads mostly did not, because a smelter or a mine behaves predictably during a disturbance.
Data centres behave differently. A hyperscale facility sits behind rectifiers, UPS systems and switch-mode power supplies. Those front ends are designed to protect the IT load, not the grid. When voltage dips during a transmission fault, a UPS will often transfer to battery within a few milliseconds and stay there until it decides the supply is healthy again.
One facility doing that is a nuisance. Several hundred megawatts doing it at once, across a cluster of sites in the same part of the network, is a sudden load rejection. Frequency rises, voltages swing high, and generators that were dispatched to serve that load now have to back off fast. NERC's incident review of a July 2024 event in Northern Virginia describes about 1,500 MW of voltage-sensitive data centre load disconnecting after a single 230 kV line fault. AEMO's concern is the same pattern in the NEM, where data centre connection enquiries now run to tens of gigawatts.
So the policy intent is simple. If a load is large enough to move system frequency or voltage when it trips, it should be required to stay connected through disturbances it can survive, and to tell the network how it will behave.
Thresholds and Tiers in the Draft Rule
Until now the working figure has been 5 MW, the screening threshold for inverter-based loads in AEMO's system strength impact assessment guidelines and the figure the 2025 consultation worked from. The draft rule put a definition in the Rules for the first time and lifted it to 30 MW.
| Tier (draft) | Size | What the draft proposes | Status |
|---|---|---|---|
| Tier 1 | Below 30 MW | Not classed as a large inverter-based load. Load-specific standards only at the network service provider's discretion | Draft only, verify against final |
| Tier 2 | 30 MW to 100 MW | Classed as a large inverter-based load. The network service provider can apply the new standards, with ride-through and information provision at the core | Draft only, verify against final |
| Tier 3 | 100 MW and above | Automatically subject to the full set of new Schedule 5.3 access standards | Draft only, verify against final |
Two things are worth noting about these tiers.
First, the thresholds were contested. Some energy-user groups argued in submissions that capturing loads below 100 MW would add cost and red tape for little system benefit. Others argued the definition should depend on how the load connects, for example whether its grid-facing interface uses actively controlled converters, rather than on size alone. Either argument could shift the final numbers.
Second, size is measured at the connection point. A campus built in stages can start in one tier and finish in another. If your master plan ends above 100 MW, design the first hall as though the full standards apply.
Technical Requirements in Engineering Terms
The draft borrows its structure from the generator access standards in NER Schedule 5.2.5, adapted for load. If you know how AEMO Generator Performance Standards work, the shape will be familiar: an automatic access standard, a minimum access standard, and room to negotiate between them.
Disturbance ride-through
This is the centre of the rule. A large inverter-based load would need to remain connected through defined voltage and frequency disturbances rather than disconnecting or transferring to backup. In practice that means:
- Riding through voltage dips caused by faults elsewhere on the network, for the duration and depth set out in the standard.
- Riding through frequency excursions and rate of change of frequency events without tripping.
- Tolerating multiple faults in a short period, which is where many UPS and protection schemes are weakest.
The exact voltage-duration envelope and frequency limits are among the details most likely to be refined in the final rule. Do not design to numbers quoted second-hand.
Active power recovery
Staying connected is not enough if the load sits at near-zero consumption for seconds after the fault clears. The draft requires consumption to be restored within defined timeframes after a disturbance. For a data centre, that is a control question: how fast the rectifiers ramp back to full draw, and whether the UPS returns load from battery to mains in a single step or a controlled ramp.
Too slow and the load behaves like a trip. Too fast and a large step increase can itself disturb a weak network. The right answer depends on the system strength at the connection point.
Reactive power and voltage behaviour
Power electronic loads can draw or inject reactive power during and after a fault, and that behaviour affects how quickly voltage recovers. Expect the network service provider to ask how the facility behaves during low voltage, whether it contributes to delayed voltage recovery, and what reactive capability it has in steady state.
Models and information
The draft requires large inverter-based loads to give network service providers and AEMO detailed information on how they respond to disturbances. For tier 3 at least, that points toward the same kind of model package generators provide: site-specific RMS models for PSS/E and, where the network is weak or the plant is complex, EMT models for PSCAD.
The hard part is that most UPS and rectifier vendors have never been asked for a validated grid model. On generation projects, getting accurate inverter models from OEMs is routinely one of the slowest steps. Our overview of PSS/E and PSCAD modelling explains what a usable model package looks like.
Related Rule Requests to Watch
ERC0394 is not the only change aimed at large loads. Two further workstreams are moving at the same time.
Operational visibility
On 21 July 2026 AEMO lodged a rule request on the operational integration and visibility of large inverter-based loads (ERC0455). The aim is for AEMO to see what large loads are doing in real time, and to know in advance when they plan to ramp, test or switch to backup. The request also proposes registration and classification of large loads, and a public register, hosted by AEMO, of existing and prospective large loads. For a data centre this points to SCADA and telemetry obligations similar to those already placed on scheduled generators.
Network cost recovery
Separate rule requests deal with who pays for network augmentation driven by large loads. The AEMC published a consultation paper on cost recovery for network augmentations on 24 September 2026. These do not change the technical design, but they will change connection budgets and the commercial case for building out a site in stages.
What This Changes in a Data Centre Design
The rule moves several decisions that used to sit only with the IT and mechanical teams into the grid connection scope.
| Design area | Before | Under the draft standards |
|---|---|---|
| UPS and rectifier specification | Chosen for IT reliability and efficiency | Must also meet ride-through and recovery behaviour, with vendor evidence |
| UPS transfer settings | Transfer to battery at the first sign of a sag | Settings coordinated with the ride-through envelope |
| Protection settings | Under-voltage and frequency trips set conservatively to protect equipment | Coordinated so the site does not trip inside the required envelope |
| Reactive compensation | Sized for power factor and harmonics | Also assessed for fault and post-fault voltage behaviour |
| Model deliverables | Simple load model, if any | Validated RMS and possibly EMT models |
| Commissioning | Electrical and IT acceptance testing | Likely to include disturbance response verification |
The practical levers are the UPS and power conversion tender, where ride-through, recovery and model deliverables are cheapest to secure, and a protection coordination study that checks every upstream trip setting against the required envelope. Connection studies for a 100 MW-plus site will look much like a generator's, so build that time into the program. Our article on data centre fault ride-through covers the physics and these design levers in detail.
The renewable energy obligations for data centres add a further layer if you plan on-site solar or a battery, because those assets bring their own generator performance standards.
Engineer Your Data Centre Connection
Getting the UPS specification, protection settings and models right at design stage costs far less than fixing them during a connection assessment or after a trip.
ElectraGlobe provides data centre grid connection engineering: connection applications, access standards compliance for inverter-based loads, and power system studies in PSS/E and PSCAD. If you have a site under assessment or an enquiry already lodged, talk to our team about where the access standards will bite.
Frequently Asked Questions
What counts as a large inverter-based load in the NEM?
Under the AEMC's March 2026 draft rule, a large inverter-based load is a load of 30 MW or more that connects through power electronics, such as a data centre or hydrogen electrolyser. The consultation stage had worked from 5 MW. The draft splits loads into three tiers: below 30 MW, 30 to 100 MW, and 100 MW and above. The final definition and thresholds may differ, so check the AEMC's final determination.
Do the new access standards apply to existing data centres?
Access standards in the National Electricity Rules have generally applied when plant connects or is altered, not retrospectively to plant already in service. Whether and how the large-load standards apply to existing facilities, or to expansions of them, depends on the transitional provisions in the final rule. If you are planning a new hall or an increase in maximum demand, assume the expansion may be assessed against the new standards.
What is ERC0394?
ERC0394 is the AEMC's reference for the rule change "Improving the NEM access standards, Package 2". It combines rule requests from AEMO and others, and its main new element is a set of access standards for large inverter-based loads. The draft was published on 12 March 2026. The final determination was targeted for 29 October 2026, but none had been published as at 6 November 2026.
Will data centres need PSCAD models?
Large data centres should expect to provide dynamic models, and the draft rule requires detailed information on how a facility responds to disturbances. RMS models for PSS/E are the likely baseline. EMT models for PSCAD are likely where the network is weak, the plant is large, or the network service provider asks for them. Ask your UPS and rectifier vendors now whether they can supply validated models.