A widely repeated figure holds that the two Firmus facilities (St Leonards and Bell Bay) would together draw close to 15% of the power Tasmania’s grid can supply. The number is a reasonable shorthand, but it compresses several distinct concepts. This explainer separates them. DII takes no position on any individual project.
Why this matters
The claim that data centres would use 15% of Tasmania’s grid is neither wrong nor quite right; it depends on which measure of the grid is used and what new generation gets built. Those conditions are the real things to scrutinise. This explainer separates the concepts so the debate can focus on them.
What the facilities would draw. St Leonards is approved for ~90MW in Stage 1 (44MW in Stage 1a), with a further ~300MW second stage planned subject to approvals. The proposed Bell Bay facility (GEE01) is ~288MW. Full build-out across both sites is therefore several hundred megawatts of near-continuous load — data centres run at high load factors, unlike most industrial users.
What Tasmania’s system can supply. Tasmania’s generation is dominated by hydro — more than 2,600MW across 30 stations, with long-term average inflows equivalent to ~9,000GWh/year — plus ~568MW of wind and the 500MW Basslink interconnector. The energy constraint is real, not theoretical: very low rainfall in 2024-25 produced the lowest on-island hydro generation in 20 years. Two different denominators matter and are often conflated: installed capacity in MW — what can be generated at peak; and annual energy in GWh — what can be generated over a year, which for hydro is limited by rainfall, not turbines.
Why the distinction matters. A 380MW+ combined load is modest against installed peak capacity but significant against annual hydro energy, particularly in dry years. Tasmania’s hydro storages have recently been managed for firming rather than baseload, which tightens the energy budget further. Whether new load is “manageable” therefore depends on what new generation is built, Marinus Link timing and the commercial terms of supply — questions currently under negotiation between Firmus, Hydro Tasmania and TasNetworks and not yet public.
The factual bottom line. The 15% figure is neither scaremongering nor spin: it is roughly right as a share of energy at full build-out under today’s system and too high if new generation and interconnection arrive as planned. The honest answer is conditional and the conditions — new generation commitments, tariff terms, curtailment provisions — are the things worth scrutinising in the approval process.
The Digital Infrastructure Institute is an independent research and education organisation. It takes no position for or against individual projects and accepts no proponent funding.
Sources: DCD — Firmus 288MW Bell Bay; DCD — St Leonards approval; Hydro Tasmania — power stations; RenewEconomy — hydro storages shift to firming; Tasmanian Economic Regulator — Annual Energy Security Review 2024-25; IEA Hydropower — Hydro Tasmania fleet