[defrost]

At the cost of building enough solar and wind farms to supply the nation I would guess, with additional costs to upgrade the distribution infrastructure for smarter load balancing, etc.

It's quite possible Portugal has put out a white paper on their transition toward renewable energy that you can find with some hunting about.

Wikipedia has a rough overview that'll provide some points to drill down further into if you're interested in the per capita comparative costings of a hybrid national power scheme.

https://en.wikipedia.org/wiki/Renewable_energy_in_Portugal

[sigmar]

Is this the paper you're referencing or something else? "long-term strategy for carbon neutrality of the portuguese economy by 2050" [pdf, english] https://unfccc.int/sites/default/files/resource/RNC2050_EN_P...

[defrost]

At a glance it looks like a paper worth reading so yes, that's the kind of paper I'd chase down (and still look for others).

Most countries have policy and costing papers, most companies file technical reports with stock exchanges, fossil fuel companies such as BHP have fat technical reports on the energy demands that they meet and project - these are all sources for hard data that can be compared (after normalising for apples V oranges).

The US is a mixed bag - Federal infomation is free and transparent, digging into details can get harder. The UK has a good civil service that puts out a lot of infomation on things that affect policy - from crime to consumption to energy use.

My comment was intended to encourage the user asking "at what cost" to form a better question and pursue their own answers.