I have to admit this is not my field of expertise, so I'm happy to stand corrected if I'm wroing and learn about it.

Spain is a net energy exporter, meaning throughout a whole year it exports more than it imports.

Agreed.

It means that the price of electricity in Spain is more often than not lower than the one in the surrounding countries.

This is where I have trouble.

I assume we have a constant energy production, which comes from different sources like nuclear. Then we have variable (but controllable) energy sources that we can turn on and off based on our demand. And then we have things like wind, solar, etc. which will produce energy according to factors out of our control.

The picture I have in my mind is this:

• In some parts of the day, our constant sources + variable sources are enough to meet our demand, and we don't need to import or export anything.
• In other parts of the day, our constant sources + unpredictable sources produce more than we need, so we have to sell.
• Finally, in some parts of the day our constant sources + variable sources + unpredictable sources are not enough to meet our demand, and we have to buy. Maybe this is where I'm getting it wrong, as I think you're implying that we could always produce more if we wanted to, but it's just cheaper to import.

Now, I assume the price at which we import or export energy depends on the usual supply + demand chain, which should leave us very exposed when we don't have enough capacity to produce what we need, and would also force us to export at low prices when we have an excess.

The way you explain it is as if an interconnecting system is a bad thing, but it is actually the reason why France can allow itself to generate so much nuclear. And it lowers, not rises, the electricity price overall.

So you're saying that France can afford to have such a constant production of nuclear energy because they have lots of places to export to when there's an excess, right? And this lowers their energy costs because relying more on nuclear comes out cheaper than relying more on other variable sources, correct?

To make the point you wish to make, you would need a graph of nuclear generating according to demand, which you wont find. The graph you show has wind generating the same or more as nuclear.

Yes, I'm fully aware of that. I understand nuclear is just a constant source of energy, for good or bad.

My point was that it seems to me (maybe wrongly) that most of the energy coming from wind is wasted because it comes when we don't need it, so we have to sell low.

So then you're telling me that, when we buy energy, it's not because we can't produce more but because it's cheaper, so we just don't use our combined cycle plants?