Something I've wondered for a while: if the whole continent is on a synchronized grid, how can countries tell to or from whom they're exporting and importing electricity. I can see how they can measure their total imports or exports by comparing generation to consumption, but how do they figure out which neighbour they're getting electricity from / sending it to?

For completeness - that's just one grid included in this viz, for the map of the different european grids see: https://en.wikipedia.org/wiki/Synchronous_grid_of_Continenta...

(Russia is another big chunk of Europe but not included in the above map, though I think it may be the same grid with the Baltics)

For the question, measuring the flow of electricity is just normal power engineering, your home electricity meter does it as well. It's not so much the countries doing it though.

You can measure the flow of power by calculating the vector product of the current and voltage in the power line. EEVblog has a very good explanation video how this is done in an (analog) domestic watt-hour meter: https://www.youtube.com/watch?v=P_3DXcB9-xE

It's a fair question. Energy charts has both the physical flows and trading charts for Germany.

E.g. trading https://www.energy-charts.info/charts/energy/chart.htm?l=en&...

Physical flows https://www.energy-charts.info/charts/energy/chart.htm?l=en&...

And it's not the same, so sometimes there is just "transit", although transit here should I guess be understood very loosely. I also assume they just know who paid for what.

Edit: although upon re-reading I think you probably asked something else. Sorry in that case.

By measuring current flows across the wires.

Each country works as a free market (inside a rails defined by their national agencies), where energy providers aim to offer a price low enough to be among the cheapest to cover the energy consumption forecast.

For those countries connected, those providers can participate in other markets. France power plants can sell energy to Spain, but not to Portugal.

The trick here is that the price each opperator's offer is somewhat calculated based on opportunity cost. Wind turbines has no opportunity cost, since not selling the energy generated from the wind now does not make them able to sell it in the future (that energy can not be stored at industrial level). Then, all the accepted offers for a given forecast are paid at the price of the most expensive offer among them.

There are five synchronous areas in Europe, the largest one being the synchronous grid of continental Europe [1].

Each national grids has interconnections with other grids and you can measure the flow of power through these interconnections to know who is sending electricity or getting electricity from neighbours.

[1] https://en.wikipedia.org/wiki/Synchronous_grid_of_Continenta...

> how can countries tell to or from whom they're exporting and importing electricity.

In terms of market deals, TSOs can't really do that. What can be done is measure the power flowing in lines connecting two grids, and summing them you get the total power exported from one grid to another.

Do you mean, for example, that the UK is importing energy from France, but where are they importing it from?

You don't. You guess based on generation, consumption and where the power lines are hooked up.