LITTLETON, Colorado, Dec 17 (Reuters) - One of the world's largest oil, gas and coal importers - Japan - has cut fossil fuel electricity generation to the lowest levels in more than a decade so far in 2025, thanks in large part to an ongoing recovery in nuclear power output.

Japan's fleet of nuclear reactors has generated the largest amount of electricity this year since 2011, when a tsunami triggered a meltdown at the Fukushima power plant and sparked a curtailment of most of the country's nuclear reactors.

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Alongside record renewable energy output, Japan's nuclear rebound has supplied utilities with the largest volume of clean power since 2010, and allowed power firms to cut the use of gas-fired power plants to the lowest in at least six years.

Japan's energy transition momentum away from fossil fuels will likely accelerate further in 2026 as the country restarts the world's largest nuclear reactor at Kashiwazaki-Kariwa and brings on additional renewable energy generation capacity.

For natural gas exporters, the steady decline in fossil fuel generation in such a prominent economy will be a cause for concern, and will likely force them to seek out other buyers for the extra gas supplies they plan to market in 2026 and beyond.

CLEAN MOMENTUM

Japan's electricity generation system has sharply boosted output from a slew of clean power sources so far in 2025.

During January to October, generation from bioenergy plants, nuclear reactors and solar and wind farms all increased by at least 10% compared to the same months in 2024, data from Ember shows.

Bioenergy and solar power sources also registered their largest-ever shares of total utility electricity supplies, at 7% and 14% respectively, while nuclear reactors generated over 10% of total utility electricity for the first time since 2011.

In all, total clean electricity output during the first 10 months of 2025 was 326.3 terawatt hours (TWh), a 9% jump from the same months in 2024 and the highest during any full year since 2010.

NUCLEAR DRIVE

The steady return of Japan's nuclear reactor fleet has been a major driver of the clean power supply growth seen in recent years.

Following the total shutdown of the country's 54 reactors in 2014, Japan's authorities have gradually resumed reactor output with generation climbing from less than 5 TWh in 2015 to close to 78 TWh so far in 2025.

Japan has restarted 14 of the 33 reactors that remain operable in the country, and plans to reboot two of the reactors at the Kashiwazaki-Kariwa nuclear power plant over the coming months.

Further restarts of idled nuclear capacity are expected, as Japan's new Prime Minister Sanae Takaichi made pledges during her campaign to boost local electricity supplies, lower electricity costs and reduce fossil fuel imports.

Japan spent 10.7 trillion yen ($68 billion) in 2024 on imported liquefied natural gas and coal, a tenth of its total import costs.

Those import tallies look primed to decline going forward as the country's supplies of power from its nuclear plants and clean energy assets continue to grow.

Gas and coal exporters may take a hit as Japan's imports shrink, but as utilities lift electricity output from nuclear reactors and cut back on output from plants that burn imported gas, Japan's power supplies should get both cleaner and cheaper.

The opinions expressed here are those of the author, a columnist for Reuters.

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https://www.reuters.com/business/energy/japans-fossil-fuel-power-output-sinks-again-nuclear-rebound-2025-12-17/