Controversial Marinus Link notches up an “offshore electricity” first for Australia as it clear... - Renew Economy

The Marinus Link undersea interconnector between Tasmania and Victoria has cleared a regulatory hurdle, marking the first time Australia has approved an offshore electricity cable. The project aims to export renewable energy from Tasmania's wind and hydro assets to the mainland grid.

Where this fits

Marinus Link is a bet that Tasmania's weather-dependent generation can supply mainland demand at scale. It exposes two structural costs the renewable transition has underestimated. First, the cable itself, a long, specialised asset in deep water, is capital-heavy and sits idle when wind or hydro output falls short, yet must be paid for regardless. Second, it commits Australia to reliance on Tasmania's finite water storage and wind patterns to firm the eastern grid, a concentration risk that leaves no margin for drought, calm weather, or supply-chain failure on the generation side.

What it means

Marinus Link will add hundreds of millions in sunk cost to the grid without adding firm capacity. Tasmania's hydro fleet is already committed to local demand and export; the link assumes surplus generation that depends on rainfall timing and wind speed. If renewable output falls short, as it does seasonally and in high-pressure systems, the mainland will still need gas peakers or imports. Australia is building transmission infrastructure to move weather-dependent power across state lines while the fuel source itself remains uncontrollable, and betting that no alternative (such as firm, dispatchable nuclear generation) exists under law. The real cost is the whole system built around scarcity, not the cable alone.