Electricity is a very special commodity. At any given moment, the amount of power fed into the grid must correspond exactly to the amount of power demanded. To balance supply and demand, electricity is constantly transported from one place to another. If the demand in one region exceeds the local production, electricity needs to flow from another region where sufficient unused generation capacity is available. Consequently, our electricity grid does not end at the Swiss border. It is connected to neighboring countries at 41 points. In this integrated system, electricity flows across the Swiss borders at all times and Swiss utilities are constantly involved in European electricity trading.

The trade between our European neighbors and the general interconnection within Europe is based on the same idea. The European integrated grid, which currently involves over 30 countries, dates back to 1958, when the 220-kilovolt grids of Germany, France and Switzerland were interconnected in Laufenburg, Switzerland (Swissgrid, 2024a). Since then, the European countries have further developed their electricity systems. This interconnection not only enables countries to trade electricity but it also reduces the likelihood of power outages because, for example, if there are any problems with a line, a number of alternative lines are available. These and many other advantages offered by electricity trading increases security of supply and reduces costs for all participants.

Imports and exports are an ordinary element of electricity markets

Goods are imported when it is cheaper than producing them locally. This basic economic logic also holds in electricity systems. Due to the differences in the availability and costs of energy sources across different regions and countries, it is beneficial to trade with each other. One country is able to use its own coal or gas deposits, while another has good geographical conditions for developing hydropower. With the transition to a renewable dominated energy system, cross-border electricity trading will become even more important. The potential of local renewable technologies hinges on the respective geographical and weather conditions: wind turbines without wind or solar cells without sun do not generate any electricity. This dependency is reduced in a common international electricity grid that is stretched to such an extent that the weather conditions within its area differ.

Swiss utilities are by no means just importers in the European power trade. Switzerland was a net exporter of electricity in eight years of the last two decades (BFE, 2024a). Even during winter months, exports are frequently made to neighboring countries in daily trade. During this time of the year, however, imports typically exceed exports overall and electricity is imported on a net basis (LINK to BLOCK I).

Electricity always flows across borders

In the integrated European grid, electricity crosses national borders at all times. These electricity flows are only partially controllable, because for physical reasons electricity always takes the path of least resistance and knows no national borders. Some of the electricity flows are caused by trade, while others are result of the interplay between local production and demand. For example, when electricity is traded between two countries only some of it takes the direct route. Another part flows via neighboring countries, as all possible connections between the countries will be used – at least partially. Those flows are usually termed loop flows (they loop around the main connection, see the flow through country C in Figure 6). Another potential case of such flows are transit flows – electricity that needs to cross another country to reach its destination (the flows on the direct connection through country D in Figure 6). This is similar to a north European tourist transiting across Switzerland for their holidays in Italy. Switzerland is amongst the European countries with the higher amount of those loop and transit flows as a large amount of German and French exports towards Italy transit trough or loop over Switzerland (e.g., in 2023 transit flows amounted to ca. 21.6 TWh while the total net-export position of Switzerland was just about 5.9 TWh, Swissgrid 2024). Unavoidable for physical reasons, those electricity flows affect the availability of transmission lines for other electricity flows.

The constantly changing flow of electricity in all directions across national borders once again illustrates that electricity is a particular commodity. Even if Switzerland would stop trading completely, there would still be electricity flows across our borders.

Swiss hydropower is an important flexibility provider for Europe

Our large seasonal storage lakes and our pumped storage hydropower plants is not only important for covering demand in Switzerland but also the basis of Switzerland’s ability to export electricity whenever Europe needs more energy. The electricity systems of most European countries do not have comparable flexibility capacity, which is why Swiss hydropower operators are ‘problem solvers’ in the larger European electricity system (Weigt et al., 2022). They produce on short notice during hours when prices are particularly high, e.g., the supply situation in Europe is critical. The European system benefits from these capabilities even though Switzerland is a small country compared to the EU. Switzerland’s integration is therefore not only important for Switzerland, but also for the other participants in the European integrated grid.

For the energy transition Switzerland will need to electrify more sectors of the economy – notably mobility and heating – increasing the demand to 75-95 TWh by 2050 (SWEET-CROSS, 2023). At the same time nuclear power is projected to be phased out in the long run. The resulting need for replaced and increased generation will be primarily provided by renewable energies, mainly solar PV. Thus, the question of how an electricity system with large shares of weather dependent renewable generation can maintain its supply security arises. It has become a focal point of political debates and a central research question not only for the Swiss energy research community.

Electrification will reduce fossil fuel imports

To achieve the net-zero target, fossil fuels will have to be replaced primarily by domestic energy from renewables. Consequently, the electrification of the Swiss energy system will gradually reduce the dependency on fossil fuel imports in general. It is uncertain whether there will still be imports of fuels such as synthetic fuels and hydrogen and if so to what extent.

The latest in 2050 there should be no more fossil fuel imports. The amount of imports until 2050 will be impacted by the speed of renewables replacing fossil fuels. Switzerland will depend on foreign countries as long as oil, natural gas or nuclear fuels remain in use, as we have no local sources for those.

Furthermore, supply security will also depend on the diversity of energy sources in the emerging technology mix, which could consist of a mix of many energy sources, for example hydropower, wind, solar, biomass, waste, or synthetic fuels.

Electricity trade will remain important

The main pillars of the future Swiss electricity supply, hydropower and PV, both have their production peaks in summer, while electricity demand is higher in winter than in summer. And due to the electrification of heating winter demand is expected to increase further. This is another reason for electricity exports and imports remaining an important aspect of Swiss electricity supply in the future, complementing our domestic sources of flexibility like hydropower.

The net import position (i.e., the difference between all imports and exports over the year) in 2050 depends on which types of renewables are used more and which are used less. Consequently, there exists a large range of projected net imports across current studies (Schwarz et al., 2023; Panos et al., 2023; BFE, 2021; VSE, 2021). These model calculations result in net electricity imports of between 0TWh and 16TWh in 2050. For comparison: In the last decade, Switzerland had a maximum of 5.6 TWh as net import, while in half of the years, there was an export surplus of up to 6.3 TWh in 2019 (Figure 8). On the fossil fuel side, the imports in terms of crude oil and oil products (ca. 100TWh) and natural gas (ca. 30TWh) in 2022 are far larger.

When analyzing the security of our electricity supply, the winter half-year is a particular focus in the political and research domains. On average, run-of-the-river hydropower and solar energy produce less electricity in winter, when demand is highest because we need to heat buildings. The opposite holds for the summer months (see Figure 8). One of the main questions for the future Swiss electricity system is therefore how to ensure sufficient supply in winter months.

Hydropower remains our security backbone

There is agreement among most Swiss energy scenarios (Schwarz et al., 2023; Panos et al., 2023; BFE, 2021; VSE, 2021) that Swiss utilities will continue to import more electricity from neighboring countries than they export during the winter months, regardless of the overall yearly trade balance. Assuming sufficient import opportunities with our neighbors, the Swiss Electricity System Adequacy study (Weigt et al., 2022), which examine the sufficiency of electricity supply in 2035 and 2040, show that the Swiss electricity supply is secured. This conclusion is robust even in extreme situations such as a particularly cold winter in Europe, two-week dark doldrums in Europe (cloudy skies, no wind), an outage of all Swiss nuclear power plants, a sharp reduction in electricity production from nuclear power in France, and a delayed expansion of the electricity grid.

The robustness of the Swiss electricity system is based on our large share of flexible hydropower units. These units allow Switzerland to focus its imports on times whenever there is energy available in the European grid (i.e. due to surplus from renewable energy production or low demand levels), even if this should be only for shorter periods. Whenever neighboring countries are unable to deliver, the stored water in reservoirs (from the spring melt and summer months) serves as a reserve that we can use to cover our own demand needs. Thanks to this flexibility, Swiss utilities generally are able to supply sufficient electricity even at times of very high demand. Pumped-storage hydro stations and the increasing shares of batteries add to this by providing additional short-term flexibility. Any additional local generation during winter (i.e. from wind, alpine solar, biomass etc.) enhances the overall hydropower flexibility further by providing more ‘maneuvering range’. In effect, even extreme situations can be withstood. It is essential that imports are generally possible throughout the winter (i.e. a proper integration into European trading mechanisms and sufficient free cross-border capacity for trade flows) and less important that they are available at any specific hour.

Less demand and more supply during winter frees up flexibility potential

If imports are significantly limited for whatever reason, critical situations can occur, but even then there are further management options to prevent or limit potential disruptions:

1. Reducing energy demand in winter relaxes the overall supply situation: As the future electricity demand is assumed to increase due to additional heating and mobility demand, improving our efficiency and conversation efforts in energy demand will be important. Studies suggest that with social innovation and cultural change, wellbeing for all can be achieved in Switzerland with significant less energy than today (Millward-Hopkins et al., 2020; Nick, 2024).
2. Increasing domestically generated electricity: Any additional kWh produced during winter frees up hydropower production for situations when electricity supply is scarce. Thus also south facing PV panels on rooftops contribute to enhancing winter supply security. Wind turbines produce a higher share of their yearly output during the winter months and are a potential complement for systems with a high PV share. Similarly, solar panels in alpine regions also supply significantly more electricity in winter because the conditions for photovoltaics in winter are better in mountain regions (e.g., see Trutnevyte et al. 2024). Additional thermal power plants could also generate electricity in winter. To avoid the emission of greenhouse gases, these would have to be operated in a climate-neutral manner. This could be achieved for example with synthetic fuels, green hydrogen, or biogas. If these fuels would be provided domestically, large additional capacities for generating renewable energy and storage would have to be built up first, which would likely be very expensive (Bauer et al., 2022). If these fuels were imported, Swiss electricity suppliers would remain dependent on supplies from abroad. The risk of supply disruptions due to external influences or political decisions is considered higher for fuel supplies than for electricity (ESC, 2023). Natural gas power plants could be operated in a largely climate-neutral manner if it were possible to capture and safely store the CO₂ produced. However, they would also have to be supplied with imported fuel. Also nuclear power plants would need to be supplied with imported fuel.
3. Storing summer surplus production for winter: Due to the seasonality of PV production there is the theoretic potential to transfer any surplus in output during summer for later usage in winter. However, for both pumped-storage hydropower and battery technologies it is unlikely to be economically viable to store very large amounts of electricity to compensate for the seasonal fluctuations (SCNAT, 2022; Bauer et al., 2022). Those units are better suited to manage the short term hourly and daily fluctuations in electricity systems. Renewable electricity surplus in summer could theoretically be used to produce hydrogen or synthetic fuels, which could then be stored and used later to generate electricity in power plants. However, it remains to be seen whether these technologies can be operated economically in Switzerland (SCNAT, 2022; Bauer et al., 2022, https://nexus-e.org/syngas-report).

Given the continued importance of electricity trade for both Switzerland and our neighbors, a good relationship between Switzerland and the European Union is important in the energy context. Despite the continued physical electricity exchange, there is—to date—no bilateral electricity agreement with the EU. Consequently, Switzerland is also not involved in the political decisions for completing the EU’s harmonized single market for electricity. To understand whether Switzerland will be able to rely on imports from Europe one needs to identify whether 1) there is enough electricity available in the European system when it is needed in Switzerland, and whether 2) the Swiss utilities have access to the European electricity market to import this electricity to Switzerland.

Renewable dynamics also shape the European electricity system

Switzerland is not alone on its path to net-zero by 2050. Europe also has ambitious plans for its energy system transformation. As with Switzerland, this European transformation will lead to a renewable dominated electricity system as backbone of the overall energy system. Consequently, the European system will also have a stronger weather dependency than today.

A mixed renewable system comprising all available sources is better suited to satisfy demand at all times. If the countries have different renewable portfolios, this increases the likelihood of regional surplus that can be exported. Figure 9 shows an exemplary monthly production and demand structure for Switzerland and its neighboring countries. Naturally, this example does not predict the future. The energy systems of Switzerland and its neighboring countries could develop differently, as not all countries have yet decided which steps they want to take to achieve the common goal of net-zero.

In addition, Europe’s large size allows more diversity even within the same renewable technologies (i.e. cloud and wind conditions are not uniform across Europe; see e.g. Grams et el. 2017). This increases the chances for surplus energy in Europe during some points in time in any season, which in turn enhances the import potential for Switzerland; in other words, there is likely enough energy in Europe for the Swiss needs even in renewable dominated systems.

The European Union is committed to moving forward with its energy transition

The European Union is moving ahead with its market integration and system transformation. The Clean Energy Package regulatory program, which the member states must implement by 2025, contains measures to enhance trade between EU member states (European Commission, 2024). The status of non-member states has not yet been clarified. To meet the underlying obligations, cross-border echange with non-member states could potentially be impacted leading to less electricity trade with Switzerland. This would mean that capacities for imports and exports would diminish. Furthermore, as a result of increased trade within the EU, the Swiss grid could be burdened by a rise in additional electricity flows in forms of loop and transit flows (Link to above).

A bilateral electricity agreement between Switzerland and the EU would facilitate cross-border electricity trading and strengthen the security of electricity supply (Frontier Economics, 2021). Contracts under private law between the Swiss transmission system operator Swissgrid and the neighboring electricity regions are also helpful. Some of these have already been signed but do not provide a long-term reliable basis. It is not only Switzerland who has an inherent interest in a comprehensive agreement, but also the EU. Swiss hydropower is in demand in Europe because most member states lack its flexibility in their electricity systems. However, if the neighboring countries expanded their own flexibility reserves in the form of electricity storage, the value of Swiss storage power plants could decrease (Schwarz, 2022).

In general, the European Union will move forward with its energy transition. Switzerland needs to take those developments into account.