Blackouts, What Causes Them?
By Dr. Lars Schernikau
On 28 April 2025 the world was jolted back to reality when Spain and Portugal witnessed the most severe blackout in Europe in decades and only a few days later on 2nd May the island of Bali also went dark.
If you rely on electricity…and who doesn’t, this isn’t just another energy think piece. It’s a reality check. I write about what causes blackouts, why they’re increasing, and what simple steps individuals, engineers, and policymakers can take now to avoid a dark and fragile energy future.
Blackouts are an uncomfortable subject. We understand the crucial aspect of a functioning power system … without which elevators, traffic lights, schools, trains, hospitals, sanitary systems, electric vehicles and gas stations, even heat pumps and of course the internet and our phone network have no way of functioning.
My blog unpacks the escalating risk of blackouts through real-world examples, from the 2025 collapses in Spain, Portugal, and Bali to the historic 2003 New York event. It breaks down the root causes, from human error and weather extremes to grid design flaws, and explains the rising threat of brownouts as a more common, managed alternative to a full collapse.
We will explore how inverters, essential for solar and wind, can destabilize the grid, and why traditional rotating mass still matters for inertia and stability. Spain’s blackout becomes a key case study, revealing how too much non-synchronous generation leads to chaos. I also question whether new tech like grid-forming inverters and flywheels can realistically save us, and shows what it takes to restart a grid once it fails.
In the final section I address energy security, weighing the hard trade-offs between “renewables”, conventional fuels, and nuclear. This is just a clear look at the fragile future of our power systems, and what must be done to keep the lights on.
As is often the case, some of what I write may be unpopular, but it is not motivated by politics nor financial gain, it is motivated by truly making a positive difference to our societies… by securing reliable, usable energy that is affordable and comes with the least possible environmental impact.
What happened in New York in 2003 and in Spain in 2025?
When communication, transport and all electricity dependent systems fail, our brains plays tricks on us… all kinds of horror-thoughts go through our minds when either stuck in a dark, hot elevator or when one cannot reach loved ones. Exactly this kind of Blackout hit Spain and Portugal on 28th April 2025! Only days later, on 2nd May 2025, the entire island of Bali also experienced a Blackout.
Don’t forget about the large New York or Northeast Blackout in 2003, where large parts of the Northeast US was without power, impacting 50 million North Americans. Subsequently “Reliability First”, a government organization, was founded to ensure that such events never happen again… Reliability First authored this video commemorating the 20th anniversary of the New York Blackout (YouTube here [1]) that is worth watching.
The New York blackout in 2003 can largely be attributed to software failures, human error, and inadequate tree trimming near power lines. [2]
The Iberian blackout in 2025 – also affecting 50 million people – can be largely attributed to power oscillations or variations that may not be that uncommon. It seems that the grid system was not able to “smoothen” out these oscillations leading to a cascading effect of grid portions shutting down within seconds.
It appears that the first potential mistake made by the Spanish grid operator “Red Electrica” was to have an electricity mix with a low percentage of dispatchable power and the second is to, simultaneously have a very low percentage of generation providing synchronous rotating inertia… more on this later.
Only 15% of generation, seconds before the blackout, came from nuclear and gas-fired power stations which operate large rotating masses. Consequently, in just five seconds, Spain lost practically all of its power.
- Note: officially only 60% of national electricity demand [6] was lost, but in reality it appears that most of Spain went dark.
- Officially, solar was still providing 3% of power at 10.45pm, see Figure 1, which is highly questionable at that time of night.
Figure 1: 28 April 2025 – Spanish generation at 10.45pm 13% from solar? [8]
The Bali blackout on 2 May 2025 appears to have been caused by disruption in the subsea cables which connect the electricity system in Bali with Java island, triggering blackouts in a number of areas in Bali. [3]
These three blackouts are just a fraction of the story, but countless others are out there if you care to search. The causes being either (1) human error or sabotage, (2) weather, or (3) system related. The risks of human error and sabotage we have to mitigate as best we can. System related risks we can avoid by thinking critically and ensuring the financial and human resources to execute a risk mitigation or – in some instances – risk elimination plan. Weather we cannot control but we can also adequately prepared with backup and reserve margins.
Below, some additional blackout examples of the past 10 years, not in order of importance and not exhaustive [4]:
Figure 2: Some additional blackout examples of the past 10 years
Figure 3: Pre-Event Oscillations in the Iberian Grid [11]
You can read the complete commentary at The Unpopular Truth.
Lars Schernikau is an energy economist, entrepreneur, commodity trader, book author, and proud member of the CO2 Coalition. He has worked at the Boston Consulting Group in the US and Germany and is co-founder, shareholder, and former supervisory board member of two Germany listed commodity companies.