REN Hires Iberdrola's Tâmega Dams for 5 Million Euros to Restart Portugal's Grid if Another Blackout Strikes
The grid operator has awarded a five-year black start contract to Iberdrola's Tâmega hydro complex, its third after Alqueva and Baixo Sabor. In April 2025, Portugal had to restart from Tapada do Outeiro and Castelo de Bode.
REN, the company that runs Portugal's high-voltage grid, has awarded Iberdrola a five-year contract worth about 5 million euros so that the Spanish group's hydroelectric complex on the Tâmega river, in the north, can help restart the national grid if the country suffers another total blackout. The deal was reported on Monday by Expresso and followed up by ECO and Jornal de Negócios.
The service is called arranque autónomo (black start): a power station able to switch itself on with no electricity from the grid, then feed power out to restart everything else. According to the reports, the tender was launched in August and the contract was awarded on 14 October. Iberdrola runs three dams in the Tâmega complex.
Paid to be ready, whether or not the lights go out
Iberdrola will be paid for keeping the complex available even if no blackout happens during the contract, Negócios reports. The price came in 39 percent below the tender's base price of 8.25 million euros, and EDP also showed interest, according to the Expresso figures cited by ECO.
The Tâmega deal adds to two black start contracts REN already holds. Both appear on the public procurement portal: one with Hidroeléctrica do Guadiana for 5,438,315 euros, covering the Alqueva I and Alqueva II hydro plants, and one with Movhera for 2,889,759.57 euros, which ECO says covers the Baixo Sabor dam. Both were signed in July 2024 after a public tender and run from 1 January 2026 to 31 December 2030.
The signed 2024 contracts show how the service works. A plant earns its availability payment only after passing qualifying tests, and only for each quarter-hour in which the service is fully available. REN can fine the operator if the plant is unavailable or fails to start. Any electricity produced during a real restart is paid at the Portuguese day-ahead market price. The newer Iberdrola contract was not yet published on the portal on Monday morning, so its own terms could not be checked.
Why it matters after 28 April 2025
When the Iberian blackout hit at 11:33 on 28 April 2025, Portugal had to restart from a total blackout using only its own power stations, while Spain could draw on France and Morocco, REN said that day. The gas-fired Tapada do Outeiro plant was the first to use its black start capacity, bringing power back to parts of Greater Porto, REN reported; it said the Castelo de Bode hydro station, helped by some links to Spain, would then bring power back further south. Every extra plant able to start on its own gives the grid operator more places to begin from.
What it means for you
- There is nothing for households to do: this is an emergency service bought by the grid operator, not a deal with any electricity supplier.
- If the grid collapses again, northern Portugal gains a further starting point for restoring power, alongside the Alqueva and Baixo Sabor plants already under contract.
- A blackout of that kind still counts as an exceptional event. As we reported, each electricity customer lost about 10 hours of supply to the 2025 blackout.
