Switzerland’s nuclear policy contains an important contradiction. The country decided after Fukushima to prohibit new reactors, yet it still relies on four operating units for a large share of its electricity. Those plants may remain online while regulators consider them safe, but the oldest will close in the early 2030s. Concerns about winter supply, imports and future demand have therefore reopened the question of whether a permanent new-build ban is sustainable.
This is not yet a nuclear revival. Switzerland has no approved replacement reactor or active construction project. The immediate debate is whether utilities should once again be allowed to apply for permission to build one.
Four Reactors Support a Hydropower-Dominated Electricity System
Switzerland operates four reactors at three stations. Beznau 1 and Beznau 2 are pressurized water reactors in Aargau, each providing about 365 megawatts of net capacity. Gösgen in Solothurn contributes about 1,010 megawatts, while Leibstadt, also in Aargau, is the largest unit at approximately 1,233 megawatts. Combined capacity is just under 3 gigawatts.
The reactors generated almost 23 terawatt-hours in 2024, equal to 28.4% of domestic electricity production. Hydropower remains the largest source, but nuclear energy supplies steady output that complements reservoirs and run-of-river plants. This combination has helped Switzerland maintain a low-carbon power system without relying entirely on variable wind and solar generation.
The fleet is small enough that one long outage can change the national balance. Gösgen remained offline for about ten months while work was completed on its feedwater system and other upgrades. The nuclear regulator approved its restart in March 2026 after reviewing the modifications.
Mühleberg, Switzerland’s fifth commercial reactor, stopped operating in 2019 and is being dismantled. Its closure showed that one plant can leave the system without an immediate crisis, but replacing several reactors within a short period would be a much larger task.
Beznau’s Closure Dates Put the Replacement Question on a Clock
Beznau is among the world’s oldest operating commercial nuclear sites. Its units entered service in 1969 and 1971. Operator Axpo plans to keep Beznau 2 online until 2032 and Beznau 1 until 2033 before beginning full decommissioning.
Together, the units provide 730 megawatts. That is far less than Leibstadt, but their output remains valuable during periods when hydropower production is lower and electricity demand is high.
Switzerland does not impose a fixed reactor lifetime. Continued operation depends on safety requirements, upgrades and proof that aging equipment remains reliable. Gösgen and Leibstadt may therefore operate beyond Beznau, but every extension requires investment and cannot provide a permanent answer.
Renewables will cover part of the replacement need. Solar capacity is growing quickly, and hydropower will remain the system’s foundation. However, solar output is strongest in summer, while Switzerland is most exposed to import dependence in winter. Reservoirs, transmission links, demand management and efficiency can narrow the gap, but Beznau’s closure schedule has strengthened the argument for keeping a nuclear option available.
The New-Build Ban Is Back Before Parliament
Switzerland’s current restriction began with the policy response to Fukushima. The Federal Council chose a gradual phase-out in 2011, and voters approved the revised Energy Act in 2017. Existing reactors received no fixed closure dates, but replacements could not be licensed.
The position began to shift as European energy markets tightened and electricity-security concerns grew. In August 2025, the Federal Council adopted an indirect counterproposal to the “Stop Blackout” initiative. Rather than supporting the initiative’s constitutional language, it recommended changing the Nuclear Energy Act so that new reactors could again be licensed.
The proposal would remove a prohibition; it would not approve a plant, choose a site or guarantee financing. Any project would still require an investor, safety and environmental reviews, planning approval and a credible waste strategy.
Parliament had not resolved the issue by June 2026. The Council of States voted in March to remove the ban. The National Council then voted narrowly in June to return the proposal to the Federal Council for more work, including greater detail on financing and the relationship between nuclear construction and renewable expansion. The Council of States rejected that delay, sending the dispute back to the lower chamber.
Switzerland has therefore moved from treating the phase-out as settled policy to debating the conditions under which it might be reversed.
Winter Electricity Security Is Driving the Reconsideration
The strongest case for retaining nuclear power concerns seasonal security rather than annual totals. Switzerland can export electricity during favorable periods and import it when domestic production is insufficient. Winter is the main vulnerability because demand rises while river flows and solar production are lower.
Cross-border trade is a major strength. Switzerland is connected to the continental European grid and plays an important role in regional electricity flows. Imports, however, cannot be treated as unlimited firm capacity. Neighboring countries are also electrifying transport, buildings and industry, and several markets may experience tight supply during the same cold period.
The wider Swiss energy system remains heavily dependent on imported oil, natural gas and nuclear fuel. Electrification can reduce fossil-fuel use, but it will increase demand for dependable power. Nuclear supporters present new capacity as insurance against excessive winter imports. Opponents argue that large reactors are too expensive and slow, and that solar power, efficiency, storage and stronger connections offer a more flexible path.
This explains why the present debate centers on optionality. Removing the ban would permit project investigation without committing Switzerland to construction. Keeping it would require long-term planning to exclude nuclear replacement even if demand or regional conditions change.
Waste Disposal Continues Regardless of the New-Build Decision
Switzerland must manage radioactive waste whether it builds another reactor or completes the phase-out. Nagra, the national waste-management cooperative, has selected Nördlich Lägern in northern Switzerland as the proposed location for a deep geological repository.
Nagra submitted its general licence application in November 2024. Federal authorities are reviewing it, with a government decision expected around 2029 and public participation forming part of the process. The repository is intended for both high-level and lower-level radioactive waste.
The project is essential under either policy path. Ending nuclear generation does not remove the need for a permanent solution to existing spent fuel. Authorizing new reactors would require Switzerland to show that additional waste can be handled without weakening safety standards or postponing responsibility.
Switzerland Has Reopened an Option, Not Started a Building Program
Switzerland’s four reactors remain valuable, but the fleet is approaching a period of change. Beznau has closure dates, Gösgen and Leibstadt require continuing investment, and winter security is becoming more important as the economy electrifies.
The country has not decided to replace its reactors. It is deciding whether replacement should remain legally possible. Even if the ban is removed, a project would face difficult questions about cost, ownership, construction time and public acceptance. The near-term strategy will still depend on safe operation of the existing fleet, renewable expansion, hydropower flexibility and European grid connections.
Switzerland’s nuclear future will be decided in stages. The first decision is legal. The harder questions—who would build, who would pay and whether nuclear could compete with other sources—would come afterward.
