Just after 12:30 PM Spanish time on April 28, the lights went out across the Iberian Peninsula.

A widespread black-out left Spain, Portugal and parts of southwestern France without electricity supply for several hours, stranding travellers in subway networks, snarling traffic, and depriving millions of people of broadband coverage and internet access.

The exact cause of the power outage remains uncertain, although government investigations are ongoing. Preliminary findings from Red Electrica (BME:REDE), Spain’s partly state-owned national electricity grid operator, have ruled out the possibility that the power outage was linked to cyber-attacks or unusual weather.

Several theories have been put forward, including an oversupply of solar power, unexplained oscillations in the grid, and poor grid management, analysts at Bernstein flagged in a note to clients.

These have yet to be proven. But what is known, the analysts at Bernstein said, is that 15 gigawatts of electricity generation — equivalent to around 50% of Spain’s power demand at the time — were lost from the electrical system within a matter of seconds.

Spanish Prime Minister Pedro Sanchez has vowed that “all necessary measures” will be taken to prevent another outage, while his Portuguese counterpart Luis Montenegro said he has asked for a European Union agency to carry out an independent audit of the incident.

Whatever may be revealed about the cause of the incident, the Bernstein analysts argued that Iberia’s black-out should serve as a “wake-up call” to electricity transmission system operators and European policymakers alike, adding that it “will certainly increase the focus on strengthening the power grid and improving its flexibility and resilience”.

Heightened spending on grids will be “front and center” in order to better match power demand with the available supply, the brokerage said. The relative disconnect of the renewables-heavy Iberian Peninsula to the rest of the European power grid will likely be in focus as well, as the stability of a larger electricity system is easier to maintain, they added.

“Electricity network companies in our coverage should therefore benefit from a favourable policy backdrop for accelerating investments,” the analysts led Jorge Alonso Suils said.

The need for enhanced grid stability and resilience is tipped to particularly benefit Red Electrica, with potential investments by the Madrid-based group now seen rising above current expectations of roughly 8.7 billion euros between this year and 2030.

A cap of annual investments in regulated networks is also projected to be lifted or removed completely by Iberian governments “shortly”, the analysts said, noting that this will provide a boon for companies like Endesa (BME:ELE), Iberdrola (OTC:IBDRY), Naturgy (BME:NTGY) and EDP (ELI:EDP) — all of whom are seen investing close to 20.2 billion euros in electricity distribution grids by the end of the decade.