Coal and gas still ran most of Japan's grid in March as nuclear stays sidelined

Coal and gas still ran most of Japan's grid in March as nuclear stays sidelined Latest generation data show thermal fuels dominating Japan's power mix, keeping Tokyo baseload supported even as policy targets renewables and data-center demand climbs. Coal supplied 32.43% of Japan's electricity in March (2026-03) and gas a further 31.30%, Ember data show, leaving the two thermal fuels in command of the grid while nuclear managed just 8.94%.³ That balance sits awkwardly against the official plan. Japan's latest energy strategy targets renewables at 40-50% of generation by 2040, up from around 25% last year, yet solar reached only 8.81% in March (2026-03) and nuclear remains far below its pre-Fukushima role.³ By 2010 Japan ran 54 reactors that supplied some 25% of its electricity, and the government once aimed to lift that to around 50% by 2030.³ Fifteen years after Fukushima the share sits near a third of the 2010 level, and the Kashiwazaki-Kariwa station, the world's largest nuclear plant, remains the test case as local opposition and regulatory review keep its restart uncertain.³ Gas demand is tied to the power sector, which absorbs roughly 55-65% of consumption.¹ Japan imported 66.3 Mt of LNG in 2025, down 1.5% on the year but still the world's second-largest volume after China, with about 98% of domestic gas demand met by imports.¹ The counterweight to falling consumption is demand from data centers. Wood Mackenzie projects it will more than triple from 19 TWh in 2024 to between 57 and 66 TWh by 2034, accounting for 60% of Japan's power demand growth as hyperscalers commit US$28 billion.⁴ The government has named Oracle, Google and Microsoft as official cloud providers, anchoring that investment and putting a floor under baseload that policy targets cannot quickly remove.⁴ Storage projects took roughly 60% of successful bids in the latest fiscal-year capacity auction, a sign investors treat intermittency as the binding constraint.² But storage smooths peaks rather than replacing round-the-clock thermal output, so coal and gas keep running through the night and prolonged low-solar spells.² The bearish case on Tokyo baseload rests on policy decarbonisation and a gradual nuclear comeback.³ Yet the March mix points the other way: thermal fuels still supplied close to two-thirds of generation, a share not falling fast enough to hit the 2040 renewables goal, let alone the 70% penetration Lawrence Berkeley National Laboratory researchers argue is achievable.³ The signal that would shift the balance is the pace of reactor restart approvals.³ Each unit cleared cuts the gas burn needed for baseload and narrows coal's role as a swing fuel; without that momentum, the targets stay aspirational and data-center growth keeps Tokyo baseload supported.^4,3