Beznau’s announced retirement comes before the new reactors in our schedules. Secure its replacement independently. Its two units produced an average of 5.56 TWh a year in 2021–2025, including outages. Growing demand adds to the task.

Electricity suppliers need ordinary winter supply. The country also needs standby cover when normal supply fails. Paying for emergency readiness alone does not replace a retiring plant’s everyday production.

Beznau’s recorded output Retirement and conditional delivery dates

Cover Beznau before the first new station

Contract the replacement independently of the new-nuclear schedule. The timeline uses Beznau’s recorded output to show the scale of that task. Growing electricity demand and dependable winter delivery add requirements beyond this historical energy comparison.

Historical output · conditional delivery datesReplacement supply must arrive firstBeznau's announced retirement years precede all three first-new-reactor cases. The intervening supply needs its own contracts and projects.

Axpo plans to retire unit 2 in 2032 and unit 1 in 2033. The full annual replacement scale reaches 5.6 TWh after both retire, using their 2021–2025 average output.

  1. Favourable caseFirst operation: 2042
  2. Planning illustrationFirst operation: 2047
  3. Delayed caseFirst operation: 2053
Separate replacement supplyConditional first new station
What the timeline counts

Unit 2's full-year contribution is removed from 2033 and unit 1's from 2034. The illustration holds each unit's 2021–2025 output average constant and sums until the year before new commercial operation.

It excludes partial effects in the final operating years, growing demand, network losses and seasonal timing. New operation marks a milestone; it does not guarantee that one station covers the full electricity and winter-capacity need. The dates have no assigned probabilities.

Historical output and delivery assumptions Timeline arithmetic and annual rows

Our base plan replaces Beznau on the announced retirement dates. ENSI says the licences have no fixed expiry date, subject to safety. Axpo nevertheless assessed operation beyond 2033 and rejected it on technical, organisational, regulatory and economic grounds. A further extension would require a safe, funded alternative supported by the owner. We credit no post-retirement output while that is absent.

ENSI: licence duration and safety conditions Axpo: decision and alternatives examined

Two jobs: replace energy and cover emergencies

Replacement supply provides electricity routinely after a plant retires. Emergency reserve stands ready for periods when the normal supply is insufficient. Buying one does not automatically provide the other. A contract must state the available power, energy duration and conditions for delivery. The federal reserve proposal itself separates payment for availability from the costs of activation.

Availability contracts and activation, sections 3.2.3 and 3.2.13

Our recommendation is to secure both services. Build useful domestic generation, retain European trade and pay willing hydro owners and customers for defined flexibility. Give reserve providers enough income to keep capacity, staff and fuel ready, with payment tied to the promised service.

Owner costs, water value and income boundaries

Emergency cover has two parts: power ready at once if a plant suddenly stops, and sustained energy if repairs take weeks or months. The 2035 chapter treats them as separate services.

What we should buy before Beznau retires

Electricity suppliers should assemble the ordinary winter supply; Swissgrid should procure the emergency reserve under ElCom’s requirements. Our preferred bridge combines paid hydro shifting, deliverable wind and winter solar, and contracted imports. Prepare permitted thermal generation as the fallback if these offers leave a dependable-supply gap.

Existing hydro and imports up to 2 GW are already counted in the supply cases. Contracts secure those assumed services. Closing the displayed gap requires additional winter energy, extra import access or less demand; buying the same water twice cannot do it.

Proposed purchasing approach; quantities and dates depend on signed offers
ServiceWho supplies and buys it?Delivery condition
Water held for winterHydro owners sell seasonal delivery to utilities.Existing reservoirs can contract earlier than new dams. Pay for foregone sales; specify starting water, minimum stock, turbine access and drought allocation.
Winter generation and importsPlant owners and foreign sellers contract with utilities.Count only projects ready by the required year. Foreign energy and border capacity must both remain available during a cold spell.
Ordinary thermal fallbackA permitted operator sells winter energy; the purchasing utilities carry the agreed volume and price risk.Secure site, emissions compliance, fuel and resupply before counting delivery. Emergency-only permissions cannot establish ordinary sales rights.
Standby power and paid demand reductionSwissgrid buys regulated reserve; utilities can also contract customer flexibility.Specify response, duration, fuel or charging needs and penalties. A short-duration battery does not supply an entire winter.

As a scale anchor, 1 GW running continuously through the 2016/17 winter supplies 4.4 TWh. The proposed 583 MW federal reserve could supply at most 2.5 TWh if it ran all winter. Its 16-day fuel requirement and emergency purpose are much narrower.

Cost anchors and import conditions

The federal reserve proposal implies about CHF 215–249 per kW-year for readiness, depending on the contingency allowance. Fuel and activation are additional. This is a benchmark from one procurement, not a quote for the larger requirement.

For gas, our illustrative activation cost is CHF 165/MWh: CHF 65/MWh fuel, 55% efficiency, CHF 10/MWh upkeep and CHF 100 per tonne of CO₂. Supplying the 2050 programme’s 4.64 TWh example this way emits about 1.7 million tonnes of CO₂ from combustion. Capital, fuel logistics and upstream emissions remain additional.

Our 2 GW import ceiling is a stress assumption, not a forecast or a border rating. ElCom tests materially different cooperation and network conditions. The electricity agreement can improve coordination and market access, but cannot guarantee foreign generation. The EU 70% rule concerns cross-border market capacity; it does not reserve 70% of a Swiss border for imports.

Electricity Supply Act, Articles 8a and 9 · Reserve contracts and fuel · Cost and fuel arithmetic · ElCom import assumptions · Electricity agreement · The 70% rule

A reserve needs power as well as energy

A plant can offer high power but run out of fuel. A battery can respond quickly but empty before the shortage ends. A useful contract specifies both how much power arrives and how long it lasts.

Our 2035 supply cases show a winter energy need before any prolonged reactor outage. They also test a chosen 90-day outage; its duration and timing have no assigned probability.

Ordinary supply and the chosen outage test

Stored energy needs charging time. Hydro has finite water and competing uses. Fuelled backup needs stocks and resupply that work during the same crisis that restricts electricity imports.

Fuel shortages and logistics, section 3.2.10

Pay reserve providers for readiness and for electricity delivered. Specify response, usable power, duration and replacement arrangements if the service fails. The final purchase needs joint tests of weather, outages and grid access.

Pay for readiness and account for fuel

Retain fossil-fuel backup as a contingency where it prevents involuntary supply cuts. Price its availability, fuel, emissions and permitted operating conditions explicitly. Use domestic low-carbon production to reduce the frequency and volume of its use. This is our recommendation; the required quantity still depends on the supply mix and stress tests.

Real Swiss proposal · June 2026Pay for readiness, then pay for useThe proposed main credit covers construction and availability of 583 MW for 15 years from around 2030. Fuel and activation costs sit outside this amount.

CHF 2'180 million requested

Construction and availability
CHF 1'880 million
Planning contingency
CHF 300 million

Preparation advances; the main credit remains deferred

Position on 29 September 2026: the main construction-and-readiness credit remains deferred pending further ElCom supply-security evidence.

Separately, the National Council approved CHF 131.3 million on 28 September, according to Keystone-SDA. Council of States approval remains pending.

Preparation and advance work
CHF 100 million
Monthey interim reserve
CHF 31.3 million

These credits advance planned work. They do not establish that the new plants are ready to supply electricity.

Keystone-SDA: National Council decision Parliament: separate credits and deferred main decision

The modelled 2050 reserve example above has different demand, capacity and import assumptions. This programme's budget cannot simply be multiplied to price that example.

Who pays, what is included and fuel security

The main request includes VAT and its stated planning contingency. Fuel and energy-balancing costs during activation are extra. Annual availability payments cover readiness and repayment of investment. Electricity consumers ultimately pay through the electricity-reserve tariff.

The supplementary credits bring planned spending forward, with later costs adjusted. Counting them again in a complete project budget would double count that work.

The message specifies fuel on site for 16 days and secured resupply logistics for 10 weeks. These are contractual obligations; actual availability still depends on delivery and operation.

The proposed plants primarily use hydrotreated vegetable oil (HVO). The message describes diesel or light heating oil as fallback if HVO cannot be replenished, with emissions obligations. Combustion and fuel supply remain part of the environmental and sovereignty assessment.

Synthetic fuels made from hydrogen offer another possible future supply route, distinct from HVO. On 25 September, the Federal Council declined new support instruments for now. Existing instruments and monitoring continue. That policy decision supplies no contracted fuel volume for reserve plants.

Federal Council: synthetic-fuel policy

Federal message: cost table and boundaries, sections 3.2.3, 3.2.10, 3.2.13 and 4.3 583 MW / 15-year proposal Credit status and dated evidence

Protecting supply has value even when a reserve runs rarely. Compare contracts for the same available power, duration and reliability. Calculate the cost of fuel and emissions separately, and report who pays. The cost of disruption supports serious preparedness; it does not establish that any project or price is justified.

The bridge we choose

Electricity suppliers should secure winter delivery now, while owners develop new nuclear. Buy paid hydro services, viable winter generation and deliverable trade. Existing hydro and imports already counted in the model must not be purchased twice to claim the remaining gap is closed.

Keep permitted fuelled backup where necessary. Price readiness separately from fuel, emissions and electricity delivered. Reduce its expected use as low-carbon projects enter service.

The next chapter gives quantities for the 2035 package.

References

  1. Programme assumptions, dispatch choices and cost scope
    WattInfo · Archived-input interpretation, 25 September 2026
  2. WattInfo proposed supply path: decisions and supporting calculations
    WattInfo · Proposed priorities and fixed-charging supply screen, 18 September 2026
  3. Beznau replacement timeline and reserve-supply arithmetic
    WattInfo · First replacement-and-reserve assessment
  4. Nuclear construction records and conditional Swiss delivery cases
    WattInfo · Delivery evidence, 17 September 2026
  5. Nuclear generation and capacity factors, 2016–2025
    WattInfo / Niko Storni · Historical comparison v1
  6. Visual explanations: seasonal stress, demand and storage
    WattInfo · Visual chapter data and explicit teaching assumptions
  7. Storage owner economics: historical-price benchmark
    Swiss Energy research project · Frozen research output
  8. Beznau: licence duration and safety review
    ENSI · 2024-12-06
  9. Beznau: owner decision and longer-operation FAQ
    Axpo · 2024-12-05
  10. Federal Council: reserve-plant financing proposal, June 2026
    Federal Council / BFE · 2026-06-12
  11. Reserve financing: cost boundaries and fuel obligations
    Federal Council · 2026-06-12
  12. Parliament: consideration of the main reserve credit suspended
    Swiss Parliament · 2026-08-11
  13. Nationalrat spricht Geld für Vorarbeiten für Reservekraftwerke
    Swissinfo / Keystone-SDA · 2026-09-28
  14. Erdbebenvorsorge: Private und staatliche Ansätze kombinieren
    Swiss Parliament · 2026-09-01
  15. Keine neuen Förderinstrumente für synthetische Energieträger notwendig
    Federal Council / SFOE · 2026-09-25
  16. System Adequacy 2028, 2030 und 2035
    ElCom · 2025-06-19
  17. Warum die Schweiz ein Stromabkommen braucht
    Swissgrid · 2024-03-08
  18. Die Schweiz braucht das Stromabkommen
    Swissgrid · Undated page; checked 2 October 2026
  19. Supply scale, fuel and nuclear owner-cost sensitivities
    WattInfo · 2026-10-02
  20. Electricity Supply Act
    Swiss Confederation · 2026-01-01
  21. Matched electricity, peak-power and trade comparisons
    WattInfo · 2026-10-02

Find definitions, calculations and model inputs in the source register.