From $77m to $193m: South Island households to foot grid bill

Monday, 25 August 2025

Transmission lines run across farmland in Canterbury, with the Southern Alps in the background.

South Island households face higher power bills as Transpower’s planned grid upgrade balloons from $77 million to $193m, with consumers now expected to shoulder most of the cost.

The national grid operator has lodged its $193m upper South Island grid upgrade proposal with the Commerce Commission, seeking approval to build new switching stations, upgrade transmission lines, and install voltage support equipment.

The project’s price tag has nearly tripled since it was first floated in 2022 at $77m, then revised to $164m earlier this year, and now set at $193m.

Transpower says the increase reflects a more detailed design, inflation, and the cost of keeping supply stable as demand rises from irrigation, farm electrification and population growth.

Price rise for households

But households will bear the brunt. For a typical Christchurch family, the upgrade would add about $35 to the annual power bill. The actual impact will depend on how Orion sets its tariffs and how demand grows.

In Marlborough and South Canterbury the hit per household could be higher because costs are spread across fewer customers.

Transpower says the project is unavoidable if the South Island is to keep pace with growing demand.

“With more homes and businesses switching to electricity use, and forecast electrification of South Canterbury’s farming and primary processing sectors, demand for electricity is expected to increase even further,” said Matt Webb, Transpower’s general manager of grid development.

A grid under pressure

Without the upgrades, areas north of Twizel could face voltage instability and forced outages by the late 2020s.

Without upgrades, Transpower warns parts of the upper South Island could face voltage instability and forced outages by the late 2020s.

The Transpower plan lands on top of Orion’s separate $1.73 billion local overhaul across Christchurch and Selwyn. The Orion project, due to start in 2028, could add about $8 a month to household bills.

Orion owns the local lines that carry power from Transpower’s grid to nearly 230,000 homes and businesses, meaning Canterbury consumers face higher charges from both national and local investment programmes.

It comes as electricity prices have already been climbing. New data from Statistics New Zealand shows power prices have jumped 6.2% in the past year, while Consumer NZ surveying found one in five people have experienced financial difficulty paying their power bill in the last 12 months.

Who pays, and how much

For the Transpower proposal, most of the cost will fall on consumers in Canterbury, Marlborough, Nelson, Tasman and the West Coast, where the reliability improvements are expected to have the greatest impact.

Transpower’s modelling shows Orion would face the largest overall bill at about $10.3m a year.

Alpine Energy, which supplies South Canterbury, would pay about $3.2m a year. In Marlborough, the charge is about $2.4m a year.

The Commerce Commission will consult on Transpower's $193m upper South Island grid upgrade proposal.

Some regional lines companies and industrial users say the cost allocation is unfair.

Westpower argued in its submission that the transmission pricing method penalises smaller regions.

In a submission to the proposal, Orion questioned whether the Transpower project is needed yet, citing updated forecasts that suggest some grid pressure may not arrive until the 2030s. It has also criticised the short time given to explore alternatives such as large-scale battery storage.

Is it worth it?

Major Electricity Users Group (MEUG) executive director Karen Boyes said the upgrade highlights a regulatory model that “is no longer working”.

“The risk sits entirely on consumers - they will face the cost of this investment whether the demand arises or not,” she said. “That imbalance between regulated businesses like Transpower and Orion, and the customers who have to pay for them, is becoming unsustainable.”

The $193m project is expected to future-proof supply into the 2030s, but critics warn consumers are being asked to shoulder too much of the risk.

Boyes said the sharp level of investment, based on forecasts that could yet shift, raised concerns about affordability. “Consumers are being asked to pay now for assets that future customers will benefit from, and if the demand does not turn up, households are still stuck with the bill.”

She said MEUG wanted greater use of non-transmission solutions such as batteries or smarter use of local networks before committing nearly $200m to new assets. “The investment is certainly needed for reliability, but future demand should not all fall on today’s consumers.”

Transpower maintains it has consulted widely and included $7m for “non-transmission solutions” that could help defer some work, though it says these will not remove the need for the main upgrade.

What’s at stake

Transpower estimates the upgrade will deliver a net benefit of $95m over 20 years, largely by avoiding blackouts and reducing the need for more expensive local generation during dry years.

Without it, voltage support across the upper South Island could falter during peak demand, especially in summer when irrigation pumps run flat out. The grid operator says the work will future-proof supply into the 2030s.

The Commerce Commission will now consult on the $193m proposal before deciding in 2025 or early 2026 whether it can go ahead.

If approved, work would begin soon after and be completed by the end of the decade, ahead of expected grid stability issues in the early 2030s. A second stage of upgrades may be required in the 2030s if demand keeps rising.