2026 Integrated System Plan · $16 billion of transmission on the optimal path, published 25 June 2026
Where it stands: 2026 ISP published 25 June 2026 and operative; three newly actionable projects in non-network options consultation
AEMO's 2026 ISP, published on 25 June 2026, sets the optimal development path for the NEM to 2050: about $106 billion of annualised capital, $16 billion of upfront transmission capital, a 14 per cent (6,000 km) expansion of the 44,000 km grid and $30 billion of avoided cost for consumers. Actionable status in the ISP is what unlocks regulated revenue for HumeLink, VNI West, Marinus and three newly actionable Queensland and Tasmanian projects.
The problem
Australia's transmission network was built to move power from coal basins to capital cities. The resource that replaces coal sits elsewhere: wind in western Victoria, Tasmania, New England and central Queensland, solar in the Murray and central-west New South Wales, offshore wind in Gippsland. Without new lines the cheapest generation cannot reach load, renewable energy zones fill up and curtail, and interconnectors cannot share firming capacity between regions. Transmission is also the slowest element of the transition: a major line takes the better part of a decade from identified need to energisation, faces the hardest social licence problems of any energy infrastructure, and cannot be built speculatively because network revenue is regulated. The ISP exists to solve that coordination problem, giving transmission businesses a regulatory basis to spend ahead of generation that has not yet committed.
What it does
Prepared every two years under the National Electricity Rules, the ISP identifies an optimal development path and confers actionable status on specific projects, which lets a transmission network service provider run the regulatory investment test for transmission and seek an AER contingent project determination. AEMO published the 2026 ISP on 25 June 2026 after testing around 1,000 combinations of generation, storage, network and consumer investment across three scenarios, engaging close to 2,000 stakeholders and considering more than 300 submissions. Under the Step Change scenario the path involves about $106 billion in annualised capital costs to 2050 across generation, storage, transmission, distribution and system security; the upfront capital cost of the path's transmission projects is $16 billion in today's dollars, of which $6 billion is recognised to 2050. The current 44,000 km grid expands by about 14 per cent, or 6,000 km, with more than half the new lines already under way. Committed and actionable projects include HumeLink, VNI West, Project Marinus Stages 1 and 2, Project EnergyConnect, CopperString, Sydney Ring North and South, QNI Connect and the Central-West Orana, New England and Hunter-Central Coast renewable energy zone network infrastructure projects. Three projects are newly actionable in the 2026 ISP: the Brisbane Area 275 kV Reinforcement, Central to North Queensland Reinforcement Stage 1 and the Tasmania REZ Expansion, with AEMO calling for non-network options to meet their identified need by Thursday 17 September 2026. By 2050 the path delivers about 66 per cent of capacity from wind and solar supplying 96 per cent of annual generation, rising to about 98 per cent renewable with hydro, with flexible gas providing a small share of energy but critical backup.
Market effect
Actionable status is the single most valuable regulatory event in Australian transmission, because it converts a line from a study into a fundable asset with a path to a regulated revenue determination; conversely, projects dropped from the path lose their case, and several have been removed in the 2026 plan. The build reshapes locational value: AEMO estimates transmission saves consumers $30 billion under Step Change in avoided capital, operating and fuel costs compared with a path without these investments, and every megawatt of new interconnection narrows the interregional price spread that traders and battery owners monetise. Marinus and VNI West in particular move Tasmanian hydro and Victorian wind against mainland scarcity, compressing Tasmania-Victoria and Victoria-New South Wales spreads. For developers the signal is where to site: the ISP's indicative renewable energy zone boundaries and sub-regional traces tell you which connection points will have headroom, and with 67 GW of grid-scale renewables and storage in development against 34 GW operating, access is the binding constraint. For consumers the counterpart is bills, since the $16 billion is recovered through regulated network charges, which is why AER contingent project determinations for the large projects have been contested on cost. The non-network options consultation closing 17 September 2026 is a genuine opening for storage and demand response to displace part of the Queensland and Tasmanian network spend.
Key numbers
- Annualised capital cost of the optimal development path to 2050
- About $106 billion under Step Change, in today's dollars
- Upfront transmission capital on the path
- $16 billion, of which $6 billion is recognised to 2050
- Modelled consumer saving from transmission
- $30 billion in avoided capital, operating and fuel costs
- Network expansion
- About 6,000 km added to a 44,000 km grid, a 14 per cent increase
- System mix by 2050
- About 66 per cent of capacity from wind and solar, delivering 96 per cent of annual generation
Who gains and who pays
- Transmission network service providers (gains): Actionable status underpins the RIT-T and AER contingent project revenue for HumeLink, VNI West, Marinus and the new projects.
- Renewable developers in renewable energy zones (gains): New network capacity determines which connection points can host the 67 GW in development.
- Electricity consumers (costs): Pay the $16 billion of transmission capital through regulated network charges against $30 billion of modelled avoided cost.
- Interconnector-exposed traders and storage operators (mixed): New interconnection narrows the interregional spreads that support arbitrage.
- Landholders and host communities (costs): Bear easement, amenity and land-use impacts of about 6,000 km of new lines.
- Non-network providers of storage and demand response (gains): Can bid to meet the identified need for the three newly actionable projects by 17 September 2026.
Implementation
Actionable projects proceed through the regulatory investment test for transmission, an AER contingent project determination and then construction, with cost recovery through the network service provider's revenue determination; changed circumstances between plans are handled through ISP feedback loop notices. AEMO is consulting on non-network options for the Brisbane Area 275 kV Reinforcement, Central to North Queensland Reinforcement Stage 1 and the Tasmania REZ Expansion, with submissions due 17 September 2026. Inputs come from the 2025 Inputs, Assumptions and Scenarios Report published on 31 July 2025 and its addendum of 10 December 2025, and from the Demand Side Factors Information Guidelines developed between August and December 2025 in response to a December 2024 AEMC rule change requiring better treatment of demand-side factors in the ISP. State schemes, notably the New South Wales renewable energy zone network infrastructure projects and Victoria's transmission arrangements, deliver much of the actual construction, and a ministerial letter on the New England REZ network infrastructure project is published alongside the 2026 plan. The next plan is the 2028 ISP, whose consumer panel is already established.
Concerns
- Delivery risk and cost escalation on HumeLink, VNI West and Marinus against the ISP's cost assumptions
- Social licence and landholder opposition delaying easements and approvals
- Recovery of $16 billion of transmission capital through consumer network charges
- Generation committing ahead of, or behind, the network build, producing curtailment or underused lines
- Scenario sensitivity: the path depends on Step Change demand and coal retirement assumptions
- Workforce and supply chain constraints across simultaneous multi-billion-dollar projects
Dates to watch
- 17 September 2026: Non-network options consultation closes for Brisbane Area 275 kV, Central to North Queensland Stage 1 and Tasmania REZ Expansion
- 2027: Inputs, assumptions and scenarios consultation for the 2028 Integrated System Plan
- 2028: Publication of the 2028 Integrated System Plan
Sources
- AEMO: 2026 Integrated System Plan, published 25 June 2026, with appendices and supporting materials, Australian Energy Market Operator (official text)
- AEMO: 2026 Integrated System Plan Explainer (cost, network expansion and 2050 system mix figures), Australian Energy Market Operator
- AEMO: Integrated System Plan publication series, Australian Energy Market Operator
- AEMC: Review of the Integrated System Plan framework, Australian Energy Market Commission
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