The U.S. Strategic Petroleum Reserve (SPR) has fallen to its lowest level since 1983, as inventories already depleted before the Iran war face continued pressure from emergency drawdowns.

Data released by the Department of Energy on Monday showed that SPR inventories declined by 6.1 million barrels last week, ending the period at 298.7 million barrels. According to the Energy Information Administration's (EIA) weekly data on SPR stocks, this marks the lowest level recorded since January 1983. The current inventory level represents less than half of the reserve's congressionally authorized maximum of approximately 714 million barrels, leaving a smaller buffer for future supply disruptions.

The decline comes after President Donald Trump authorized the release of up to 172 million barrels in March 2026, in response to the Iran war's impact on global energy supplies. Iranian attacks have disrupted the flow of tanker traffic through the Strait of Hormuz, a critical chokepoint through which roughly 20 million barrels of oil pass daily, accounting for about a fifth of global petroleum consumption. The Trump administration formally announced the releases on March 11, 2026.

EIA data indicates that the SPR held approximately 415.4 million barrels of oil in mid-March. As of early August, inventories have dropped by roughly 116 million barrels from that level.

History of Drawdowns

The current releases follow a multi-year period of historic drawdowns. The Biden administration authorized the release of 180 million barrels in response to Russia's invasion of Ukraine in early 2022. At the beginning of 2022, SPR inventories stood at approximately 600 million barrels and fell to 375 million barrels by year's end.

After hitting a low of about 347 million barrels in the summer of 2023, reserves gradually recovered, reaching 400 million barrels in May 2025. Inventories reached a recent peak of over 415 million barrels in February 2026, before the latest round of drawdowns commenced in March. The back-to-back emergency releases across two administrations underscore the SPR's central role as the government's primary tool for cushioning oil market shocks, but also highlight how each major drawdown resets the timeline for replenishment.

Origins and Structure of the SPR

The SPR was established in 1975 under the Energy Policy and Conservation Act, created in response to the OPEC oil embargo of 1973–74. Arab members of OPEC imposed the embargo in retaliation for U.S. resupply of Israel's military during the Yom Kippur War.

The reserve was initially intended to have a capacity of 1 billion barrels, a level it never reached. Currently, the SPR has a congressionally authorized maximum of approximately 714 million barrels. Its highest-ever inventory was 726.6 million barrels, recorded in December 2009, when the authorized capacity stood at 727 million barrels.

SPR reserves are stored at four locations, thousands of feet below ground in salt caverns. These geological formations offer advantages over surface facilities in terms of cost, maintenance, environmental impact, and security. Geological pressure naturally seals cracks that develop in salt formations, preventing oil from leaking out, while temperature differentials keep the oil circulating to maintain quality. Salt caverns can also be expanded to precise dimensions through a solution-mining process that dissolves salt using fresh water.

Oversight and Funding

In May, the Government Accountability Office (GAO) issued a report warning that Congress and the Department of Energy must develop a unified long-term plan to address the SPR's maintenance needs and establish a strategy for managing future inventory levels. The GAO's warning takes on added urgency as consecutive emergency releases have reduced the reserve well below levels historically maintained during peacetime.

The One Big Beautiful Bill Act, enacted by Republicans in Congress and President Trump in July 2025, included $171 million for acquiring petroleum products for the SPR and $218 million for facility maintenance.