Global Nuclear Capacity Stagnates with Marginal 133 MW Net Gain in 2025 as Major Reactors Retire

For all the press releases, policy reversals, and ambitious pledges surrounding atomic energy over the past year, the actual expansion of the global nuclear grid in 2025 tells a much quieter story. Despite a surge in political momentum, the world’s operating nuclear capacity grew by a razor-thin margin of just 133 megawatts (MW) last year. To put that figure into perspective, a single large-scale offshore wind turbine can now boast a capacity of 15 MW. The stagnation highlights a fundamental friction in the global energy transition: the race to build next-generation nuclear plants is currently locked in a dead heat with the retirement of the 20th-century fleet.[1][2]

The math behind the 133 MW net gain is straightforward but revealing. According to data from the International Atomic Energy Agency (IAEA) and the World Nuclear Industry Status Report, only three new nuclear reactors were connected to the global grid in 2025. These new units—located in Russia, India, and China—added a combined 2,956 MW of fresh generating capacity. However, that progress was almost entirely erased by the permanent shutdown of seven older reactors worldwide, which removed 2,823 MW from the grid.[1][3][4]

The three new additions reflect the current center of gravity for nuclear engineering. Russia commissioned the Kursk 2-1 reactor, adding 1,200 MW of capacity. India connected the 630 MW Rajasthan-7 unit, while China brought the 1,126 MW Zhangzhou-2 reactor online. These projects represent years of capital-intensive construction finally reaching the finish line, underscoring the dominance of Asian and Eastern European state-backed developers in executing large-scale nuclear infrastructure.[1][5]

On the other side of the ledger, the retirements were driven by a mix of aging infrastructure and long-standing political mandates. Belgium led the retreat by shuttering three major units: Doel 1, Doel 2, and Tihange-1. Together, these closures removed over 1,800 MW of capacity. The shutdowns proceeded even as Belgian lawmakers fiercely debated the country's broader nuclear phaseout, illustrating how difficult it is to reverse course once a plant's decommissioning process is set in motion.[1][2]

Taiwan also marked a historic milestone in 2025, permanently closing the Maanshan-2 reactor on the island's southern tip. The 938 MW unit was the last operating nuclear power plant in Taiwan, and its closure completed the territory's long-planned exit from atomic energy. Rounding out the global retirements, Russia decommissioned three tiny 11 MW units at the Bilibino plant in the Arctic, replacing them with newer floating nuclear technology.[1][2]

To understand why the global nuclear fleet is treading water, one must look at the demographics of the reactors themselves. The world currently relies on roughly 410 operating commercial reactors, but the fleet is undeniably graying. The average age of an operating nuclear reactor is now 32.4 years. More than 260 of these units have been in service for over three decades, and over 140 have surpassed the 40-year mark.[4][7]

Nuclear power plants are marvels of engineering, but they are not immortal. Components degrade under intense radiation and thermal stress, and upgrading a 40-year-old facility to meet modern safety standards often requires billions of dollars. For many utilities, especially those operating in competitive, deregulated electricity markets, the math simply does not support life extensions. As a result, the industry is fighting a constant battle of attrition, needing to build massive new plants just to replace the baseline capacity that is aging out of the system.[3][7]

This dynamic explains why the much-discussed "nuclear renaissance" has yet to materialize in actual generation statistics. While global electricity demand is surging—driven by electrification, data centers, and artificial intelligence—nuclear's share of global commercial electricity generation slipped to roughly 9% in 2024 and 2025. This represents its lowest share in four decades, a stark contrast to the explosive, exponential growth of solar and wind power over the same period.[3][7]

Yet, industry analysts caution against interpreting the 2025 stagnation as a terminal decline. The current data reflects investment decisions made a decade or more ago, owing to the notoriously long lead times of nuclear construction. Today, the pipeline of future capacity tells a very different story. There are currently over 60 reactors under construction across 15 countries, representing nearly 80 gigawatts (GW) of future capacity. This is one of the highest levels of active nuclear construction seen in the last 30 years.[2][4]

The geographic distribution of this pipeline, however, is heavily skewed. China alone accounts for roughly half of the global capacity under construction, with plans to reach 100 GW of installed nuclear capacity by 2030. Over the past decade, 94% of the nuclear reactors that began construction worldwide were of Chinese or Russian design. This shift has raised alarms in Western capitals, where policymakers are increasingly viewing nuclear energy not just as a climate tool, but as a critical pillar of national security and technological leadership.[4][5]

In response, Western nations are deploying a two-pronged strategy. First, they are aggressively pursuing Long-Term Operation (LTO) licenses to keep their existing fleets running. By extending the operational lifespan of a reactor from 40 to 60—or even 80—years, countries can preserve their zero-carbon baseload power without the crippling capital costs of new builds. The International Atomic Energy Agency notes that these life extensions are currently the most cost-effective way to maintain global nuclear capacity.[4][6]

Second, the industry is betting heavily on the commercialization of Small Modular Reactors (SMRs). Unlike traditional gigawatt-scale plants, which are bespoke mega-projects prone to massive cost overruns and decade-long delays, SMRs are designed to be manufactured in factories and assembled on-site. While China and Russia already operate early-stage SMRs, Western developers in the United States, Canada, and the United Kingdom are racing to deploy their own commercial models by the early 2030s.[4][6]

The turning point for the global fleet may arrive sooner than the SMR revolution. According to projections from BloombergNEF, 2026 is slated to be the first year in at least a decade and a half where zero reactors worldwide are scheduled for permanent shutdown. With the wave of retirements temporarily pausing, the new reactors coming online over the next few years will finally translate into pure net growth for the grid.[2]

The International Atomic Energy Agency recently revised its long-term projections upward for the fifth consecutive year, estimating that global nuclear capacity could more than double by 2050 in its high-case scenario. Achieving that, however, will require the industry to overcome its historical struggles with supply chain bottlenecks, specialized labor shortages, and financing hurdles.[6]

Ultimately, the story of nuclear energy in 2025 is one of a massive, slow-turning ship. The 133 MW net gain is a humble figure, reflecting the heavy anchor of an aging 20th-century fleet. But beneath the surface, the engines are running hotter than they have in decades. As the retirement curve flattens and the current wave of global construction reaches completion, the atomic grid is quietly positioning itself for its next era of expansion.[2][4][7]