Macron will first meet Spain’s new Socialist Prime Minister Pedro Sanchez on Thursday, then attend a state dinner hosted by King Felipe, before heading to Lisbon on Friday for lunch with Prime Minister Antonio Costa and an EU summit on improving the Iberian Peninsula's energy links with the rest of Europe.
While lacking in oil and gas, Portugal and Spain have raced ahead with developing renewable energy sources like wind and solar power, and hope to sell their surplus electricity beyond the Pyrenees.
"We are expecting concrete projects from this summit so that the Iberian Peninsula will no longer be a sort of island in Europe in energy terms," said Portuguese Foreign Minister Augusto Santos Silva.
But officials in Macron's office speak only of increasing electricity links, whereas Madrid and Lisbon want to link up gas pipelines as well.
The summit is set to confirm the Bay of Biscay project, which will stretch a high-voltage underwater cable 370 kilometres from Spain's northern coast to southwest France.
The link will nearly double the interconnection capacity between the two countries to 5,000 megawatts, and will see the EU contribute a record 578 million euros for the project.
For natural gas, Madrid is hoping to become a strategic source for Europe by pushing a pipeline project called MidCat that would link Catalonia to France, allowing it to send on some of the gas it imports from Algeria.
"But the French are not at all in favour, and the viability of this project is far from certain," said Gonzalo Escribano, an expert at the Elcano Institute.
Analysts say Spanish officials suspect that France wants to protect its sizeable nuclear power industry -- the country generates roughly 70 percent of its electricity from its 58 nuclear power plants -- and its former energy monopolies, in which the state still owns stakes, from foreign competition.
"I'm not expecting any breakthrough on the gas question, that's where the talks are going to be tough," Escribano said.
Before the summit, Macron will hold one of his trademark "citizen consultations" on the future of Europe, speaking and answering questions from dozens of young people alongside Costa.
The town-hall style meetings are seen by Macron as a way to engage people across Europe in a dialogue on the future of the EU. Strengthening and integrating the bloc has been a key objective of his presidency.