Synergy’s 142-megawatt King Rocks windfarm near Hyden will be delivered at a cost above $500 million, around $200 million higher than a price tag placed on the project in 2022.

The cost of delivery was revealed in an Infrastructure Western Australia assessment of the project plan, conducted late last year and published publicly in recent days.

The assessment placed an estimated cost of $504 million on the project, which includes 23 wind turbines with 142 megawatts of capacity, as well as connection works to existing transmission infrastructure.

It’s $200 million higher than the $300 million assigned to the project when it was put before the Shire of Kondinin in 2022 – and was recommended by the council for Regional Joint Development Assessment Panel approval.

That submission included provisions for a “maximum of 30” wind turbines along with transmission lines connecting the existing high voltage line that cuts through the area.

The scope of the work covered individually by the JDAP application and the project plan is not like-for-like, making it difficult to ascertain the exact scale of cost hikes which may have impacted the project over the past two years.

An earlier assessment into Water Corporation’s plans to develop the Flat Rocks stage two wind farm at Kojonup warned of the potential for cost and timeline blowouts as demand for renewables work in the state grows in the years ahead.

Stage one of Flat Rocks, which is being rolled out by Enel Green Power, was retrospectively approved by the WA Planning Commission in April.

IWA said Synergy’s plan had factored in schedule risks associated with connections to Western Power’s transmission network, along with staff attraction, retention and housing, community consultation and freight and logistics for the project’s enormous infrastructure requirements.

“IWA considers that there are risks to the delivery schedule, and notes that Synergy is working to mitigate these risks,” the report said.

Synergy plans to begin construction at King Rocks in 2025 and hopes to have the project up and running by the middle of 2026.

IWA noted King Rocks was heavily aligned with the state’s renewable energy push and had the potential to decrease carbon dioxide equivalent emissions in the state by around 120,000-360,000 tonnes between 2026 and 2035.

At its peak the project will have the ability to generate enough energy to power 100,000 average homes, according to the utility.

The 2024-25 state budget set aside $69 million for decarbonisation works by Synergy, a figure primarily assigned to the King Rocks project.