Keep Gösgen and Leibstadt where safety and owner economics permit. Develop two new reactors. Secure winter supply before Beznau retires.
Heating and transport need more electricity as they leave fuel behind. These three actions preserve useful production, replace retiring plants and provide a basis for that growth. Hydro, renewables and paid flexibility complete the proposal.
- 2032–2035
Keep supply ahead of retirements
Replace Beznau on its announced retirement timetable. Keep Gösgen, Leibstadt, hydro and trade, and develop 26 GWp of solar by 2035.
Buy winter electricity before the old reactors close, allowing for low lake levels and restricted imports. Buy immediate backup and sustained outage cover as separate services.
The lake range, import reliance and outage cover → - 2047–2050
Bring two new reactors into service
Our programme aims for a first unit in 2047 and a second in 2050, with overlapping construction. Begin owner-led development now, and maintain replacement supply for a delay to 2053 or later.
The programme, budget and remaining supply → - 2050
Supply an electrified economy
Plan around 94.2 TWh a year used by customers, including the programme’s data center allowance. Generation also covers losses and any net exports. Further demand growth needs additional supply.
The demand assumptions →
In the demanding 2016/17 weather case, two new units still leave 4.6 TWh missing over the year, with imports up to 2 GW and recorded October lake stocks. Additional power is also needed in cold hours. Dates and demand are planning assumptions; delays need longer replacement contracts.
Generation, water and import assumptions
Matched weather cases, nuclear dates and demand allowance · Regular supply and reserve boundaries · Nuclear schedule sensitivities
The scale of the task
The supply programme uses 94.2 TWh of customer electricity a year in 2050, including a data center allowance. It is a scenario, before grid losses. Retiring plants remove production while demand rises; expansion must address both.
Programme demand and boundariesThe demand chapter explains the growth. The programme compares reactor fleets and the electricity still missing.
The mix we recommend
Keep safe reactors
Pursue Gösgen and Leibstadt extensions early. Preserving safe, viable output reduces the production that must be replaced. Safety review and the owner’s investment case determine continued operation.
Evidence and conditionsSecure the Beznau replacement early
Beznau’s announced closure precedes our new-reactor schedules. Electricity suppliers should secure replacement delivery and separate emergency cover, without assuming the earliest nuclear date will hold.
Evidence and conditionsDevelop new nuclear
Develop two units and assess a third against the remaining winter need. Our working dates are 2047 and 2050, conditional on legal change, sites, approvals, suppliers and finance. A permitted project must carry its construction, waste and insurance obligations; extend replacement contracts if delivery slips.
Evidence and conditionsIn the demanding-winter 2050 case, two new reactors cut the electricity still missing over the year from 13.3 to 4.6 TWh. This uses 2016/17 weather, recorded October water and imports up to 2 GW, with planned maintenance and no prolonged outage. The tested solar-and-battery alternative leaves more missing annually, but lowers the largest hourly gap further in the 2011/12 cold spell.
Matched reactor and solar-and-battery packagesExpand useful hydro
Prioritise Grimsel 4’s power, Grimselsee’s storage and a viable Mattmark winter shift. Pay owners for water held back and lost sales. Current hourly cases credit no extra supply from these future projects; signed delivery and permits determine when benefits can enter the plan.
Evidence and conditionsBuild valuable renewables
Build solar and wind where useful output, connections and willing buyers justify investment. The tested 2035 package uses 26 GWp of solar. Further panels need complementary supply at night and through poor weather; a large annual total alone does not settle that need.
Evidence and conditionsUse storage for the right job
Use batteries for short gaps and contracted grid services. Their energy must come from somewhere and their owners need income. Keep bulk seasonal lithium-battery storage outside the base plan; assess heat stores for suitable heating systems.
Evidence and conditionsElectrify efficiently
Combine heat pumps and electric transport with better buildings and voluntary flexible demand. Our demand scenario already includes efficiency gains: count only further savings as reductions. Verify installed heating performance and allow separately for growth beyond the sector assumptions.
Evidence and conditionsA timetable for decisions and delivery
What should change in the 2050 strategy?
Make dependable winter supply and viable investment the organising priorities. Include new nuclear explicitly. The current policy already addresses winter imports and supply security. Our criticism concerns how generation targets, delivery and owner income fit together.
Permission needs an owner, a budget and a delivery date
The Federal Council proposed lifting the new-nuclear ban and Parliament agreed. DETEC expects a referendum vote in 2027. The ban remains in force during this process; repeal would not itself approve a plant. DETEC: vote expected in 2027
Our proposal is to turn that option into accountable project development, while buying the earlier replacement supply independently.
| Official path | What our proposal must deliver |
|---|---|
| 35 TWh non-hydro renewable generation in 2035 | Our tested 26 GWp solar fleet falls short. Even counting all other mixed generation as renewable gives only 27.5 TWh with 2016/17 weather. Keep renewable development beyond this test package; it is not a target-compliant construction plan. |
| 5 TWh winter net-import guide value | Measure net imports, gross import dependence and hourly access separately. Our 2 GW import sensitivity does not establish compliance or guaranteed foreign supply. |
| A possible return to new nuclear | Develop two standardised units, assess a third, retain safe extensions and secure supply before Beznau retires. Every project needs approvals, an owner and viable finance. |
Energy Act, Article 2 · Generation accounting and target comparison
Why our demand path differs from grid-planning scenarios
Swissgrid’s framework raises consumption by 4–16 TWh between 2019 and 2040. Our 2035 reference is about 73.5 TWh before the separate data center increment. It deliberately tests substantial heating and transport conversion earlier. The different base years prevent a direct like-for-like comparison; our demand is a planning choice, not a more certain forecast.
BFE says EP2050+ no longer reflects all recent developments adequately. Its EP2060 results are expected towards the end of 2027. Update the supply programme when stronger demand and delivery evidence becomes available.
Swissgrid demand scenarios, page 22 · Demand conversion assumptions · BFE: EP2060 work and timetable
An annual surplus is not enough
In our 2050 model, the same plants with the same shortfalls can end the year as a net importer or a net exporter. The balance depends on how much summer surplus is exported rather than left unused. Annual exports therefore do not show that winter hours are supplied.
Export ranges with equal supply shortfallsThe ETH–PSI study excludes supply stress tests and leaves the winter net-import goal outside its models. Our supply plan must additionally test restricted imports, difficult weather and coincident outages for every proposed mix.
Study scope, page 2 Winter import goal, pages 7 and 11Possible exports and the limits of the trade calculation
| Weather | Minimum | Maximum |
|---|---|---|
| 2011/12 | -8.1 | +11.6 |
| 2016/17 | -8.1 | +8.5 |
| 2021/22 | -7.7 | +7.4 |
Each range fixes annual unmet electricity, the largest hourly gap and annual gross imports at the reference values. Exports can use up to 8 GW. Demand still remains uncovered: these are possible schedules, not forecasts of a complete supply plan. Actual trade depends on prices and foreign demand.
What could change our recommendation?
We propose two new reactors as an initial programme, while keeping further units under review. The remaining hourly supply, national investment total and household tariff still need a complete portfolio assessment. The hourly screening simplifies reservoir connections and omits internal grid constraints. A buildable programme needs those physical and financial details.
A matched comparison must include the same demand, dry and cold years, correlated outages, import restrictions, grid work and retirement dates. New nuclear must carry its construction, financing, waste and insurance costs. Other options must carry their own backup, storage and connection costs.
If a permitted alternative provides the same dependable supply at lower whole-system cost and credible commercial terms, prefer it. If nuclear offers lack credible delivery or financing, revise the build programme and secure other supply. Apply the same rule to hydro, renewables and storage.
These conditions can change project selection. Reactor-extension work, efficient electrification and preparation of new supply projects should proceed while those choices are resolved.
Compare the quantities, financing and remaining supply in the 2050 programme.
References
- Winter supply, lake access and nuclear fleet comparisons
WattInfo · Calibrated hourly scenarios, 26 September 2026 - Import reliance, winter solar inputs and forced shortages
WattInfo · Archived-input calculations, 25 September 2026 - Programme assumptions, dispatch choices and cost scope
WattInfo · Archived-input interpretation, 25 September 2026 - WattInfo electricity programme: 66 hourly cases, delivery dates and owner finance
WattInfo · Conditional programme, 19 September 2026 - WattInfo: regular winter supply, immediate backup and prolonged-outage cover
WattInfo · Supply-service interpretation, 18 September 2026 - WattInfo archive-to-model checks: demand, thirteen weather years and heat storage
WattInfo · Additive model evidence review, 18 September 2026 - WattInfo proposed supply path: decisions and supporting calculations
WattInfo · Proposed priorities and fixed-charging supply screen, 18 September 2026 - 2035 day/night supply and vehicle-flexibility model
WattInfo · First 2035 supply package and 12 matched/sensitivity runs - Independent demand model v1
Swiss Energy research project · Frozen research output - Nuclear generation and capacity factors, 2016–2025
WattInfo / Niko Storni · Historical comparison v1 - Economics of extending Gösgen and Leibstadt to 80 years
BFE commissioned research · Report dated 12 March 2026; publication date not established - Mattmark: proposed dam raising
Axpo · Published 2025-01-16 - Cost comparisons: inputs, calculations and boundaries
WattInfo · Curated from the cost-metrics research package, 17 September 2026 - Storage owner economics: historical-price benchmark
Swiss Energy research project · Frozen research output - Energy Strategy 2050: Monitoring Report 2025, full report
Swiss Federal Office of Energy (BFE) · 2025 report, corrected March 2026 - Swiss solar and associated storage statistics for 2025
Swissolar for BFE · Reference year 2025; report dated 9 July 2026 - Nuclear construction records and conditional Swiss delivery cases
WattInfo · Delivery evidence, 17 September 2026 - Convention on Nuclear Safety: tenth Swiss report
Swiss Federal Nuclear Safety Inspectorate (ENSI) · Tenth report - Historical nuclear proposals: selected data and reuse assessment
WattInfo · Historical proposals, reviewed 18 September 2026 - ETH–PSI study: conditions, model inputs and reading notes
WattInfo · Study review, 18 September 2026 - ETH–PSI: Nuclear Power and the Future Swiss Energy System
ETH Zurich and PSI; 19 authors including Manera · 2026-06-29 - ETH–PSI: nuclear white paper modelling documentation
ETH Zurich and PSI · 2026-06-29 - Beznau: owner decision and longer-operation FAQ
Axpo · 2024-12-05 - Gösgen restart permission after the extended shutdown
Swiss Federal Nuclear Safety Inspectorate (ENSI) · 2026-09-26 - ENSI: followup-ensi-restart-2017-reader
ENSI · 2017-02-16 - Parliament: consideration of the main reserve credit suspended
Swiss Parliament · 2026-08-11 - Energy Act
Swiss Confederation · 2026-01-01 - Energieperspektiven 2060: purpose and timetable
BFE · Undated page; checked 2 October 2026 - Swiss energy consumption and production: nuclear policy status
DETEC · 2026-06-29 - Matched electricity, peak-power and trade comparisons
WattInfo · 2026-10-02 - Swissgrid strategic grid2040 technical report
Swissgrid · Undated page; checked 2 October 2026 - Nationalrat spricht Geld für Vorarbeiten für Reservekraftwerke
Swissinfo / Keystone-SDA · 2026-09-28 - Federal Chancellery nuclear and electricity-law referendum observations
Federal Chancellery / LINDAS · Official snapshot modified 13 October 2026; checked 14 October - Kernenergiegesetz: Referendum zustande gekommen
Federal Chancellery · 2026-10-19 - UVEK current votes: nuclear-law referendum in 2027
UVEK · 2026-10-23
Find definitions, calculations and model inputs in the source register.