Blackout: could your company survive 8 hours without power or internet?

8 min read · DataRoad

Preparing the company for a blackout It ceased to be a theoretical exercise. On April 28, 2025, mainland Portugal and Spain were without electricity at 11:33 (Lisbon time). In Lisbon, the restoration began only at 20:12. During those hours, many companies discovered that the server was down, the internet was not working, the landlines were silent, and no one knew who decided what.

The difference between stopping and continuing to work lies in simple decisions made beforehand — and that cost much less than a whole day lost.

What happened on April 28, 2025

• 11:33: General outage in the Iberian Peninsula. The European Network of Transmission System Operators (ENTSO-E) reports the incident at 12:33 Central European time.
• Throughout the day: The Government meets in an extraordinary Council of Ministers and a state of energy crisis is declared, which only ends at 23:59 the following day. The electricity system is reactivated from the Castelo do Bode and Tapada do Outeiro power plants.
• 19:25 and 20:12: According to the president of E-Redes, during a parliamentary hearing, the replacement begins in Porto and in Lisbon, respectively.
• 03:00 the next day: The supply was restored. By the end of the 28th, about 95% of the customers already had power.

In telecommunications, the report from ANACOM submitted to the Government concluded that the prolonged power failure caused a cascade effect on mobile and fixed electronic communications networks. The regulator recommended evaluating the battery and generator autonomy and defining minimum autonomy times for network equipment.

Translation for a company: It's not enough to have two tariffers of the same type. When the power goes out for hours, the operators' antennas can also fail.

What should remain connected — and what can be disconnected

It makes no sense to keep 40 fixed computers connected for 8 hours. It makes sense to keep the backbone: the network, the connection to the outside world, and the systems where the work is being done.

Example of sizing

Example — an office with 25 people on laptops and a local file server. Budget: the network UPS only powers the router, firewall, main switch, two Wi-Fi points, and the satellite antenna; the server has its own UPS that safely shuts it down after 15 minutes. Result: the team continues to work on email and the cloud during the hours for which the UPS was sized; the server restarts without damage. It costs much less than protecting the entire office.

Redundant internet: two paths that do not share the same weak point

True redundancy means that the failure of one path does not knock down the other. Two fibers of the same operator that enter the building through the same conduit do not count. A practical rule:

• Way 1: main operator fiber.
• Path 2: another operator, preferably with another technology.
• Path 3 (for those who can't stop): Satellite internet, such as Starlink, which relies less on local terrestrial infrastructure. Connected to a UPS, it keeps the office online even when local networks fail.
• The firewall It is they who decide, alone and in seconds, where the traffic passes when a road closes down.

We explain the options in more detail in the guide on Internet for businesses: speed and redundancy.

A real case: ReStream, Starlink in the office in Cascais

A ReStream, DataRoad, a Texas-based technology company and a global leader in multi-channel live streaming, chose DataRoad for the office in Cascais. The project included 3rd-layer PoE switches in the network core, Wi-Fi 6, enterprise firewall, Starlink connection for a robust and redundant connection to the internet, and permanent monitoring of the infrastructure. The management was entrusted to DataRoad under an IT Unlimited contract.

For a company whose business is to be online, “what if the internet goes down?” is not an academic question. Any SME should ask this about their office.

The example we practice: the DataRoad data center

We don't recommend what we don't do at home. DataRoad's data center has redundant internet, Starlink, and advanced renewable energy systems, and it's from it that international clients work remotely. It's this infrastructure that supports us. remote work solutions, For companies that need to continue operating when the office closes.

The plan of a page

One continuity plan It doesn't have to be an 80-page dossier. For a blackout, a printed page solves most of the problem. It must answer six questions:

1. Who decides? Name and phone number of the person who declares “we are in shutdown mode” and of a substitute.
2. How do we talk to each other? Defined message group, list of contacts on paper.
3. What stays on and for how long? The list in the table above, with the actual autonomy of each UPS.
4. Where does the team work? A house, another office or a space with energy — with remote access already tested.
5. What do we say to the customers? Ready-made message-type for email, website and social media.
6. How do we get back? Order of starting the equipment and checking that the backups have run — the method is in the article about Backup and disaster recovery.

A plan that has never been tested is just a guess. Once a year, turn off the power to the grid at the end of the day and see what happens.

How DataRoad helps

In IT Unlimited contracts, we size the UPSs, configure redundant internet with automatic switching between connections, and monitor the equipment — we know that an office went without power before the customer called us. For those who can’t stop outside of business hours, the IT Unlimited Premium 365 Includes coverage for nights, weekends and holidays. Headquartered in Alfragide, assistance throughout the country.

Frequently Asked Questions

How long did the blackout of April 28, 2025 last?

The outage began at 11:33. According to E-Redes, the restoration began in Lisbon at 20:12 and was completed at 03:00 the following day; by the end of day 28, about 95% of the customers had already had power. The duration varied greatly from zone to zone.

Does a 4G/5G router come as a backup internet connection?

It helps with everyday failures, like a cut fiber. In a prolonged blackout, the mobile networks themselves can be affected, as ANACOM concluded. For those who can't stop, satellite internet connected to a UPS is the most robust complement.

Do I need a generator?

It depends on how long you want to keep it running and what you need to be connected to. To keep the network and internet running for a few hours, a well-sized UPS is usually enough. For local servers, cold or heavy equipment for many hours, the generator becomes worthwhile.

Does having everything in the cloud solve the problem?

It solves half the problem. The data is accessible, but the team still needs power and an internet connection to get there. Cloud without redundant internet is just a safe place where they can't get in.

Test of resistance to power outages in 10 working days

We assess UPS, internet connections, critical systems, and how the team would work without power, and deliver your plan in a single page with priority fixes. For businesses with more than 10 locations · contract support · remote and on-site support.

Sources

• ENTSO-E — Blackout in the Iberian Peninsula, April 28, 2025
• Government of Portugal — Extraordinary Council of Ministers of 29 April 2025
• Government of Portugal — ANAC, ANACOM and IMT deliver reports on the impact of the blackout
• Lusa (via DNoticias) — Parliamentary hearing of the president of E-Redes on the replacement
• Lusa (via DNoticias) — REN and E-Redes: network restored to 100%