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The electricity trade determines how much electricity is imported into or exported from a country. Physically, electricity always seeks the path of least resistance.
The electricity grid directs electrical energy from the generator to the consumer, including across borders. Measuring the physical flow allows conclusions to be drawn about the actual utilisation of individual interconnection lines, the lines that connect the electricity grids of neighbouring countries. The capacity utilisation of individual lines is measured, for example.
Cross-border electricity trade and physical flow
It is important to distinguish between the Cross-border electricity trade – that is, the commercial flow – and the physical flow of electricity, since the amount of electricity traded between two countries does not generally correspond to the amount of electricity measured at an interconnection line.
Indicators of cross-border electricity trading show how much electricity Germany trades with the neighbouring countries with which its grid is electrically connected. Electricity traders do business with foreign suppliers or customers when it makes economic sense and provided that the exchanges of the countries are "coupled". This is known as market coupling. The international electricity trade is first and foremost an economic flow.
While the commercial flow comes about from the order books of the coupled exchanges, the physical flow via interconnection lines is made up exclusively of the interaction of all electricity physically fed into and taken off the system and the electrotechnical status of all interconnected grids – in short, the electrotechnical properties of the electricity system. Electricity flows through the grid in accordance with the laws of physics, always taking the path of least resistance through the lines. To do so, it allows for detours. For example, if electricity is to be transported from a generator in northern Germany to a consumer in southern Germany, some of it always flows through the grids of neighbouring countries.
Show trading and physical flows on the SMARD website
In the Market data visuals section, the Cross-border electricity trade is clearly shown in the data category "Commercial foreign trade". The data comprise the planned import and export transmission capacities for each hour shown. The data for commercial foreign trade are supplied broken down by hour and updated after each intraday session.
The physical flow through the interconnection lines between countries is also shown on the SMARD website. The Transmission system operators measure the actual flow of electricity from Germany, Austria and Luxembourg to the neighbouring countries with which they are electrically connected, and vice versa. The direction is also shown. There is therefore a value for physical exports and imports, just as for the commercial foreign trade.
The graph shows the actual physical flows of electricity from and to Germany.