Reconciling operational realities with high-flexibility green hydrogen: A case study of Australia's national hydrogen plan.

Global energy transition roadmaps increasingly rely on green hydrogen as a flexible load to mitigate renewable curtailment and defer transmission investment, yet a gap remains between grid planners' least-cost optimization and the engineering limits of large-scale electrolysis. This perspective examines the hydrogen-as-a-flexible-load strategy, focusing on technology-specific minimum stable loads and deep-flexibility risks in grid models. Australia is a pivotal case study: the draft 2026 Integrated System Plan (ISP) shifts to weekly production balancing to halve 2050 curtailment to 10%, yet relies on a technical floor unproven at scale. We identify a flexibility paradox in which electrolyzers are forced into high-frequency grid stabilization without accounting for efficiency penalties and degradation from sub-nominal cycling. Contrasting ISP targets with operational data, manufacturer specifications and project reports, we distil six variables for planning models and identify the research and policy pathways needed to keep hydrogen's grid role viable and sustainable.