Portugal just ran on 100% renewables for six days in a row

As it turned out, those rainy, blustery days were just a warmup. Portugal produced more than enough renewable power to serve all its customers for six straight days, from October 31 to November 6.

"The gas plants were there, waiting to dispatch energy, should it be needed. It was not, because the wind was blowing; it was raining a lot," said Hugo Costa, who oversees Portugal for EDP Renewables, the renewables arm of the state utility, which was privatized in 2012. ​"And we were producing with a positive impact to the consumers because the prices have dropped dramatically, almost to zero."

To hit Paris Agreement climate goals by 2050, nations need to run their grids without carbon emissions not just for three or six days, but year-round. A handful of countries already do this, thanks to generous endowments of hydropower, largely developed well before the climate crisis drove investment decisions for power plants. Others score highly on carbon-free power thanks to big fleets of nuclear plants.

Portugal falls into a different, more relatable bucket: It started its decarbonization journey with some legacy hydropower, but no nuclear capacity nor plans to build any. That meant it had to figure out how to cut fossil fuel use by maximizing new renewables.

How did Portugal make this happen? It committed to building renewables early and often, pledging a 2050 deadline for net-zero carbon emissions in 2016, several years before the European Union as a whole found the conviction to take that step. Portugal's last coal plants shut down in 2022, leaving (imported) fossil gas as the backstop for on-demand power.

"The key conclusion, in my opinion, is that it shows that the Portuguese grid is prepared for very high shares of renewable electricity and for its expected variation: We were able to manage both the sharp increase of hydro and wind production, and also the return to a lower share of renewables, when natural-gas power plants were requested again to supply some of the country's demand," said Miguel Prado, who covers Portugal's energy sector for Expresso newspaper.

The task ahead for Portugal's grid decarbonization is to reduce and ultimately eliminate the number of hours when the country needs to burn gas to keep the lights on. Leaders want gas generation, which made up 21% of electricity consumption from January through October, to end completely by 2040.

To reach its climate goals, Portugal has focused on diversification of renewable resources; instead of depending primarily on wind, water or sun, it blends each into the portfolio and finds ways to make them more complementary. The country's power companies are now chasing major additional offshore wind opportunities, expanding solar installations and repowering older onshore wind projects to get more out of the best locations.

Anatomy of a six-day clean energy streak

After the overthrow of the authoritarian Estado Novo dictatorship in 1974, the newly formed state utility Energias de Portugal constructed a series of hydroelectric dams on the once-wild rivers that rushed from the eastern mountains to the western coast. The company built its first onshore wind projects in the 1990s, when solar simply couldn't compete economically, and solar installations have only recently started to catch up.

That's why the gray skies didn't hurt overall renewable production during the country's recent record-setting stretch, as they would have in, say, California or Hawaii. The wind and hydro were cranking, and that's what mattered.

Any milestone in the rapidly evolving clean energy sector should come with specific parameters. So what exactly did the Portuguese grid accomplish earlier this month?

The six-day record refers to the 149 consecutive hours in which ​"energy from renewable sources exceeded the industrial and household consumption needs across the country." The country's previous record for that metric was 131 hours (a little over five days), achieved in 2019. That doesn't mean that fossil fuel plants weren't operating — just that the overall renewable generation more than met customer needs.

But Portugal also just set a national record for meeting the entire electricity system's needs ​"without resorting to conventional thermal power generation." This gas-free stretch started Halloween night and ran for 131 consecutive hours, about 5 days, nearly tripling Portugal's previous record of 56 hours straight in 2021. And for 95 of those consecutive hours, Portugal exported clean electricity to Spain, because it consistently had more than it needed — again without burning gas.

That trendline is the thing to watch. Renewables-friendly weather will come and go, and shoulder months are ripe for renewables to outpace consumer demand because heating or cooling needs are lower than in the summer and winter. But the last time Portugal had ideal conditions for a renewables record, it only lasted one-third as long without burning gas. As more wind and solar capacity comes online, Portugal expands its arsenal for running entirely on renewables.

This particular week stood out, but it exemplifies a historic shift in energy sources. Natural-gas use for Portugal's electricity production fell 39% year-over-year for the period from January to October, according to REN. That brought overall gas use to its lowest level since 2006.

Portugal has made grid decarbonization perfectly tangible for itself. To reach its climate goals, it needs to take the playbook from this one week in November and run it for longer periods of time, until eventually it doesn't even need gas on standby. And it has to do so even in the parts of the year when the winds and the rain don't lash the off-season traveler who'd heard so much about a climate reminiscent of Southern California.