The Iran War’s Oil Shock Is Tightening the Vise on Japan’s Sento Operators

An oil shock from the war in the Middle East involving Iran is squeezing Japan’s public bathhouses, which have already lived through decades of demographic decline, the rise of private home bathing, and two years of pandemic closures.

Global fuel oil prices have jumped since the war began, and Japan’s sento operators heat thousands of gallons of water daily using heavy oil boilers. The Japan National Sento Association told ruling-party lawmakers on April 9 that fuel costs have risen 1.4 to 1.5 times their pre-conflict levels, an increase of as much as 50 percent.

Sento operators have almost no room to pass that on.

Prefectures cap the admission price

Unlike Western bathhouse operators, who set their own ticket prices, Japanese sento operate under a postwar price regulation that caps what they can charge. Each prefecture’s governor sets a maximum admission fee under the Price Control Ordinance (Bukka Tōsei Rei), a framework originally enacted to contain post-World War II inflation. Tokyo currently caps adult admission at 550 yen (about $3.80). Other prefectures set their caps between roughly 500 and 600 yen, according to publicly posted prefectural schedules.

When input costs rise, a company like Bathhouse, which is on pace for $120 million in annual revenue, can adjust its $60-plus session fee. Sant Roch in Paris manages margins by capping capacity at half its physical seats. A sento operator in Aomori or Aichi has neither option. The ceiling on revenue is set by regulation, and the floor on costs is set by the global oil market.

Fuel is the dominant variable cost. A Teikoku Databank industry analysis published April 11 describes boiler heavy oil as the bulk of a sento operator’s expenses, and found that a 30 percent rise in fuel costs reduces the average sento’s operating profit by 30 percent, compared with roughly 5 percent for Japanese businesses overall. The sensitivity is six times the national average.

More than 60 percent of operators report worse results

The Teikoku Databank survey found that more than 60 percent of sento operators reported worsening financial results as of late March 2026, the highest share since the pandemic. Industry-wide profits for fiscal year 2025 are projected at roughly 2.7 billion yen, down from 4.9 billion yen the prior year. One in four operators ran at a loss in fiscal year 2024.

Shinichi Uno, executive director of the Japan National Sento Association, estimated that as many as one-fifth of the country’s operators have temporarily closed or slashed operating hours since the war began. One named closure and one cutback have been reported in recent weeks: Katsuragi Onsen in Aomori announced it will close at the end of May, and Ikesu Onsen in Aichi, founded in 1919, has delayed its daily opening by an hour since late March after its monthly fuel delivery was halved.

The broader decline predates the current crisis by decades. The association counted 1,562 member bathhouses nationwide in 2025, down from a peak of 17,999 in 1968. (The association count represents dues-paying members. The Ministry of Health, Labour and Welfare counted 2,847 general public baths as of March 2024, a somewhat broader category.) Roughly 95.5 percent of Japanese households now have private bathing facilities, per the ministry, so over six decades most of the customers sento once served have moved to bathing at home.

The association wants fuel subsidies, not a higher cap

On April 9, the Japan National Sento Association met with Liberal Democratic Party lawmakers to deliver a formal emergency request for government support. The federation’s ask centers on fuel subsidies and relief measures that would offset the oil price rise without requiring operators to seek approval for price cap increases, a slow and politically difficult process.

Sento occupy a distinct cultural and social welfare role in Japan. They are classified under public health law, not commercial hospitality, and many local governments view the regulated pricing as a public-access guarantee rather than a market constraint. Raising the cap, even modestly, is a decision that carries voter-facing weight. Subsidies avoid that friction but do not address the underlying structural exposure.

Fuel-fired operators with fixed prices face the same squeeze

Sento operators depend on fossil fuel boilers and cannot set their own prices. Any operator whose heating costs are tied to fossil fuel commodity prices and whose pricing power is constrained (by regulation, by competition, or by consumer expectation) faces a version of the same squeeze when energy markets spike.

Japan imports more than 90 percent of its crude oil from the Middle East, a concentration that makes sento operators unusually exposed to any disruption in the region. The IEEPA-driven tariff and trade pressure on the US and European sauna supply chain is a similar shock: policy decisions that change bathing businesses’ costs without their say.

Roughly 30 percent of Japan’s sento still rely on fuel oil boilers, according to the association. The operators that have converted to gas or electric heating face a less acute version of the same cost pressure. Changing heat source takes capital, and most operators in the industry are running at or below breakeven.

The cultural exchange between Japanese bathing tradition and the Western sauna sector has mostly been about design, ritual, and aesthetics. In 2021, a Tokyo sento owner told Reuters that his monthly fuel bill had jumped from 300,000 yen to 450,000 yen during an earlier, smaller price spike. The current shock is larger.

By the end of March 2025, Japan was down to 2,730 sento, and licensed sauna baths were close to outnumbering them, according to health ministry records.