Who actually pays for Australia's utility megaprojects

When a road or a hospital costs more than forecast, the money comes from consolidated revenue. It appears in budget papers, gets examined by an auditor-general, and can be raised in parliament.

Most of Australia's utility megaprojects work differently — and the pipeline is tilting toward them. Infrastructure Australia's 2025 Infrastructure Market Capacity Report projects utilities investment, led by energy transmission, more than doubling to $36 billion over the next five years.

Across four projects covered by this masthead, two routes emerge. For transmission, the people paying are electricity customers, and the scrutiny happens in front of an economic regulator rather than a parliament — a regulator that decides how much of any overrun customers carry. Water can be different: Western Australia is paying for its next desalination plant from the State budget.

Four projects, two routes

HumeLink — about $4.6 billion approved. A regulated asset. Through its contingent project process, the Australian Energy Regulator approved $4,573.5 million ($2022–23) of capital expenditure across HumeLink's early works and delivery stages in August 2024, against the $4.88 billion Transgrid proposed. Approved costs are recovered from consumers through network charges; spending above the allowance is not recovered automatically, but is assessed by the AER after the fact.

CopperString. The Queensland Investment Corporation's October 2025 review recommended that the Eastern Link backbone be delivered as a regulated asset, by a new regulated entity that would develop, construct, operate and maintain it. Under the recommended model the regulated asset base is set by ministerial direction under Queensland's Priority Transmission Infrastructure framework, with the AER as independent expert, while spur lines and generator connection assets — scoped at up to $1.3 billion — would be delivered by private capital on commercial terms. Under the earlier model the State would have funded the whole Eastern Link; the 2025–26 Queensland Budget allocated $2.4 billion to the project.

Marinus Link — Stage 1. Costs will be recovered through transmission charges on Victorian and Tasmanian customers once the link starts operating, expected in 2030, under an agreed allocation: Tasmanian customers carry 27.6 per cent, Victorians 72.4 per cent. In February 2026 the AER set the Stage 1 construction allowance at $3,470.6 million ($2023), giving a forecast opening regulated asset base of about $4.9 billion (nominal) in July 2030. Financial close in September 2025 secured $3.8 billion of Clean Energy Finance Corporation funding alongside equity from the Commonwealth, Victoria and Tasmania.

Alkimos Seawater Desalination Plant — $2.8 billion. The other route. The WA Government announced the plant in December 2023 as a $2.8 billion investment supported by the Budget surplus, and Water Corporation confirmed in September 2026 that it is funded from the State's budget position.

What changes when a regulator holds the pen

For anyone working on the transmission projects, three consequences follow — and they are not obvious from the outside.

Variations are harder, and slower. A client recovering costs through regulated charges cannot simply agree a variation and absorb it. Every dollar eventually has to be justified to a regulator, in a public process, with consumer advocates arguing the other way. That reduces the client's appetite for scope growth and lengthens the time it takes to settle a claim.

The cost increase is public, and so is the argument. Applications, submissions and the AER's reasoning are published. What they do not usually provide is a single, standard split showing how much of an increase is scope, how much escalation and how much delivery performance — the same gap that runs through every project in this series.

The client's incentive is to show it managed the project prudently, because that is what determines how much is recovered. That is a genuine discipline, and it shapes how clients approach both disclosure and claims.

The political economy is the real story

The transmission build-out is enormous and it is only beginning. If cost increases on the first major projects flow through to household bills, the politics of the entire program changes — and it changes at exactly the moment the pipeline is scaling up.

The first test case is under way, and it is not HumeLink. On 1 September 2026 the AER published a preliminary position on Transgrid's application to reopen its 2023–28 revenue determination for Project EnergyConnect, the 900 km South Australia–NSW interconnector. Transgrid is seeking an additional $1.2 billion ($2022–23) for the NSW component, on top of the $2.1 billion approved in 2023. The AER's preliminary view is that two of the seven reopener criteria are not met: that the "contract failure" event Transgrid relies on is not a valid reopener event, and that Transgrid has not shown that failing to deliver, or materially delaying, the project would be likely to materially affect the reliability or security of the transmission system. ElectraNet, which built the South Australian section, says it delivered that section on time and within budget.

That does not mean the company simply pays. The AER says its position, if made final, would not prevent Transgrid from recovering prudent and efficient expenditure: any overspend not approved through the reopener can be assessed in an ex post review as part of Transgrid's 2028–33 revenue determination, where the regulator decides how much, if any, is added to the regulated asset base. Submissions closed on 1 October 2026 and the final decision is still to come. The answer to this article's question is therefore a split: customers pay for what the regulator judges prudent and efficient; the network company carries what it does not. That expectation applies to VNI West, Hunter Transmission, CopperString and everything behind them.

Marinus Link shows the split being set in advance. Tasmania is about 7.5 per cent of the combined Tasmanian and Victorian population (ABS, March 2026) and its customers carry 27.6 per cent of the link's costs — an allocation the Tasmanian Government says it secured in 2022 to reduce costs for its consumers. The AER's February 2026 decision also sets how a construction overrun is shared: under its capital expenditure sharing scheme, Marinus Link Pty Ltd bears 30 per cent of any overspend up to 10 per cent of the allowance, and 10 per cent of any overspend beyond that. Settling both before construction removed major uncertainties for the project.

Water can take a different route

Alkimos shows that a utility megaproject does not have to be paid for through bills. The WA Government is funding the $2.8 billion plant from the State's budget position. Water Corporation, the state-owned utility delivering it through the Alkimos Seawater Alliance, says it is on track to be fully operational in 2028, supplying an initial 50 billion litres of drinking water a year.

Water pricing is set state by state rather than nationally, so there is no single public process comparable to an AER determination, and the funding route for a major water asset varies by jurisdiction and by project.

The comparison that makes the point

Set the four utility projects against others covered by this masthead:

M6 is the outlier and worth noting. After two subsidence events in March 2024 and a notice of default issued by Transport for NSW in March 2026, the NSW Government announced on 19 June 2026 that the CGU consortium (CPB Contractors, Ghella and UGL) would resume work under the original design-and-construct contract, would not pursue contractual claims for costs related to the subsidence events, and would rectify the affected area. The government says the agreement is at no extra cost to NSW taxpayers.

Melbourne Airport's third runway is the other end. The airport is building the roughly $3 billion runway itself, with opening due in 2031, so its cost sits within the airport's own commercial arrangements rather than a budget paper or a regulatory determination.

What to watch

1. The AER's final decision on the EnergyConnect reopener, and the ex post review in Transgrid's 2028–33 revenue determination. Together they set the precedent for every transmission project behind it.
2. Whether any Australian utility publishes a cost decomposition — scope, escalation and delivery variance separated.
3. The CopperString regulated entity, and the regulatory process that follows it.
4. How states fund and price new desalination capacity, as Alkimos and other plants come online.
5. Whether consumer advocates become a routine party to major project cost disputes. They already are in electricity.

Published 1 September 2026 · Updated 4 October 2026