# Programme assumptions and the meaning of model results

WattInfo, 25 September 2026.

The 2035 comparison contains thirteen weather years with scheduled reactor maintenance, a general output allowance and a separate prolonged-outage case. The 2050 comparison uses three selected weather years. These are conditional supply calculations. Their input assumptions require calibration before the gaps set contract quantities.

## Generation and water

The solar profile is calibrated to 1,100 kWh/kWp in 2024 weather. BFE reports 820 kWh/kW for that year in solar statistics 2025, sections 2.3 and 5.4.1. Its representative sample covers systems above 30 kVA, with production metering and twelve monthly reports; site and orientation are not separated. The national production estimate separately accounts for installations added during the year. This comparison identifies a calibration question; it does not calculate a revised supply gap or establish the yield of a future site mix.

Nuclear output allows for scheduled maintenance and derating. Long outages are modelled separately. Historical capacity factors include extended outages, so using an all-year average and imposing another outage requires explicit treatment of overlapping losses. Excluding selected years also needs a complete event record; no new outage-free average is adopted here.

Recorded examples include Gösgen's shutdown from 24 May 2025 to its grid return on 23 March 2026, and Leibstadt's major refurbishment from 24 May to 3 December 2021. These events have different causes and timing; they do not establish a probability for a 90-day winter outage. Sources: Gösgen annual report 2025, printed pages 10–11, and its 23 March 2026 restart announcement; Leibstadt annual report 2021, Das Betriebsjahr 2021, opening paragraphs. The event register preserves the dates and source locators. Leibstadt's primary-source reader extraction is archived; the original PDF download failed.

Natural-water reservoirs are pooled with finite energy and turbine limits, perfect knowledge of the year and a zero stock floor. Four pumped stores have separate power, energy and loss limits. The model does not secure water rights, operating reserves or paid access to those services. These simplified assumptions affect the remaining supply requirement.

## Timing, power and trade

The dispatch first minimises annual unmet energy, then its largest hourly value. A final weighted objective favours fewer imports and certain generation/storage flows. These priorities select a schedule without establishing when all remaining gaps must occur. Seasonal totals, day/night splits, exports and storage trajectories need separate stability checks before stronger interpretations.

A largest hourly shortfall is a power measure; it can recur. The annual or seasonal energy total answers how much electricity remains to be supplied. The two values overlap and cannot be added. Displayed original results remain conditional on their original input assumptions.

Exports are possible flows within an assumed connection limit. The programme objective makes exporting cheaper than curtailing surplus, without modelling buyers or prices. The older n8-pv26 example also uses a dispatch preference rather than a trade market. Its net-export arithmetic describes one selected schedule. Surplus could instead be left unused. Neither schedule secures sales or establishes a net-export outcome for Switzerland.

## Matched import comparison

For 2016/17 weather in the 2035 package, subtract the winter unmet-energy result at a 2 GW import ceiling from the matched result at 1 or 0 GW, then divide GWh by 1,000. Show the maintenance-only and prolonged-outage pairs separately. Case definitions, demand and options are checked for matching boundaries. These are differences between saved model results, not independently reproduced uniqueness ranges or calibrated procurement quantities.

## Costs and output value

The programme owner ledger includes waste handling/storage and decommissioning-fund contributions, but no separately identified geological-disposal contribution. That scope must be resolved before the calculation is a complete waste-funding budget. Extending reactors and adding new units also requires assessment of the resulting waste inventory and authorisations.

Break-even revenue is discounted expenditure divided by discounted generation. The example received price affects the owner's cash result, not that break-even formula. Curtailment creates a risk to saleable output and receipts, but aggregate curtailment alone establishes neither a technology's lost sales nor a market price. The separate seasonal comparison prices potential winter generation and assumes it is fully useful. It does not price the same delivered service as the hourly programme.

## Reproduction

The manifest preserves all 66 original case summaries and input hashes, plus the marginal import arithmetic. Source catalogues and original case data remain unchanged. The associated builder uses only archived inputs; it does not run the solver. New calibration, alternative-optimum ranges and new finance results require a separate evidence edition.