The Closure Scenario: What Happens to Global Energy in Week One, Month One, Month Three
The Strait of Hormuz has never been closed. The threat of closure has been used repeatedly as a diplomatic instrument by Iran, and incidents in the strait have periodically elevated insurance premiums, rerouted tankers, and spiked oil prices. What has not happened, in the modern era of global oil dependence, is a complete cessation of transit. This absence of precedent does not mean the scenario is implausible. It means that the consequences of closure must be modeled rather than observed, and the models are sobering.
In the first week of a complete closure, the most immediate effect would be on oil prices rather than on physical supply. Storage inventories, in-transit cargoes, and strategic reserves are sufficient to buffer physical shortfalls for the opening days of any crisis. The price signal, however, would be instantaneous and severe. A complete Hormuz closure would remove roughly 20% of global oil supply from the market. Futures markets would price this disruption forward, and the resulting spike — analysts have estimated effects ranging from $50 to $150 per barrel above pre-closure levels, depending on assumptions about demand response and reserve releases — would itself impose economic damage before a single refinery ran short of feedstock.
The strategic petroleum reserve releases would begin in week one. The United States, Japan, South Korea, and IEA members hold coordinated reserves that can be released in a crisis. The IEA collective reserve is approximately 1.5 billion barrels, and coordinated release mechanisms exist. However, the release capacity — the rate at which reserves can be extracted, transported, and delivered — is limited. A sustained closure would deplete accessible reserves in weeks if physical supply was completely cut.
By month one, physical shortfalls would begin to appear in the most exposed markets. East Asian refiners — particularly Japan and South Korea, which have limited domestic production and tight storage capacity — would face feedstock constraints affecting refinery run rates. The industrial consequences would be visible in production statistics and electricity generation data before they became visible in retail energy prices, because regulated or subsidized energy markets delay price transmission into consumer behavior. The underlying physical constraint would be real regardless of what the price signals showed domestically.
China’s situation in month one would depend heavily on the strategic reserve releases that Beijing would almost certainly initiate. Estimated SPR volumes sufficient for sixty to ninety days of import replacement exist in theory. The rate at which they can be deployed is constrained by the infrastructure for extracting, moving, and delivering the reserves to refineries. China’s refinery base is not uniformly positioned near its storage sites. Getting reserve crude from storage to the processing capacity that needs it is a logistics problem, not just a volume problem.
Month three is where the models diverge most significantly, because by month three the range of outcomes is determined by political variables that are impossible to model precisely. Has the military conflict that closed the strait been resolved? Has Iran agreed to terms that reopen transit in exchange for political concessions? Has the US conducted a military operation to force reopening? Has the prolonged economic disruption produced political instability in importing nations that changes the diplomatic calculus? The economic models can describe the physical and financial damage accumulating during month three. They cannot determine whether the political system will have found an exit before the damage becomes irreversible.
What the models agree on is the asymmetry of the scenario. The cost of a month-three closure to the global economy — measured in GDP losses, industrial output reductions, inflation, and financial market damage — is enormous. The cost to Iran of a month-three closure includes everything it would lose economically but also must be weighed against whatever political objective the closure was meant to serve. Iran has shown, under sustained sanctions pressure, that it is capable of accepting severe economic damage in service of political goals. The world’s assumption that economic rationality will always open the strait has not been tested. It may not hold under conditions where Iran’s leadership concludes that the alternative to closure is worse.