What would happen if there was a nationwide blackout in the UK?

Metro

28-04-2025

Trains. ATMs. Airports. Mobile phone signal. The internet. Hospitals. Banks. Schools.
Today, all of the above – and more – went dark across Spain and Portugal after both nations were hit by a major power outage.
The cause of the blackout, which happened just before midday, is not immediately clear. Portugal's grid operator, however, has said it was down to a 'rare atmospheric phenomenon' that knocked Spain's power grid.
Getting the systems online may take several hours, making it likely that the two European countries will be plunged into darkness once the sun sets.
But could this ever happen in the UK? And, if it did, what would happen?
Chris Owens is the marketing manager for Riello UPS, which manufactures power supplies and other standby power solutions.
In 2019, the company created the Blackout Report, examining the odds of the UK going dark and the consequences of this happening.
'When you look at the events in Portugal and Spain and wonder 'could that happen here in the UK?', it's still highly unlikely,' explains Owens.
'There's never been a complete failure of the UK's electricity network, our power grid is reliable and robust.'
'But we looked into the issue a few years ago for our Blackout report project, and official government risk assessments stated there was around a one-in-200 chance of a grid shutdown within five years.
'So while it's not likely to happen, the odds are considerably shorter than winning the lottery, for example.'
Owens stresses, however, that this isn't to say it can't happen; there's still a roughly 0.5% chance of Britain going dark.
A fair few things, Owens says. In 1987, a weather event simply known as the 'Great Storm' brought hurricane-force winds to parts of Britain, battering homes with 120mph gusts of wind.
Thousands of homes were left without power as ripped trees took down electricity poles, making it among the biggest blackouts in British history, according to the Blackout Report.
Extreme weather events like storms and the resulting floods can impact electricity supplies. 'As recently as August 9, 2019, 1million people around London lost power after a lightning strike took a couple of power plants offline,' says Owens.
What happens hundreds of thousands of miles away from the Earth can also threaten whether we can switch our living room lights on.
Solar flares – eruptions of energetic particles from the Sun – can crash into the Earth and cause geomagnetic storms. This is because this solar goo mingles with the Earth's invisible force field, the magnetic field.
While these storms can create the Northern Lights, they can also interfere with power, navigation and communication systems.
As Owens notes, sometimes power failures happen when the infrastructure that gets electricity to homes is damaged, like the fire at a substation near Heathrow Airport last month.
Cyber crooks could also cause power outages. In 2015, one in five residents of Kyiv, Ukraine, suffered from a blackout caused by a Russian cyber attack.
Hackers infected three energy distribution companies with sketchy software, called malware, that switched substations and emergency power stations off.
'Within hours, society would start to grind to a halt, and the most vulnerable would be at real risk.'
This is the rather sobering answer to this question from Iain Staffell, reader in Sustainable Energy at Imperial College London.
Like in Spain and Portugal, a sweeping blackout that cuts electricity to the UK would upend countless lives and vital services.
'A nationwide blackout does not just cause chaos, it is life-threatening,' Staffell, who writes on Britain's power grid for the power generation business Drax's Electric Insights project, tells Metro.
'Electricity underpins everything we rely on: clean water, heating, the mobile phone networks, banking, refrigerated food and medicines.
Owens adds that the effects of a disruption at that scale would be felt by millions of people almost immediately.
Given that the internet and mobile services, as well as other forms of media, like TV, could all go down after a blackout, it's good to be prepared.
The government recommends Britons: Keep a battery or wind-up torch (and spare batteries) at home. Also have a crank radio to hand and a written list of local and national station frequencies; this will be one of the main ways you get official information via emergency broadcasts.
Keep bottled water and non-perishable food – think cans of veg or ready-to-eat tinned meat – in your pantry.
Find out your block letter. The power grid is broken up into blocks and grid operators would schedule emergency power cuts on a rotating bases in these blocks.
Download or print out offline maps in case you do not have access to live map-based mobile application
'Mobile phone coverage would probably go within a couple of hours, electronic payment systems like card readers will stop working, traffic lights will go out,' he says.
Even a lot of gas-fired heating and cooking systems in people's homes will stop as they rely on electrical pumps or control systems to work properly.'
Resorting power is no easy feat, however. After all, with a total blackout, there's no electricity to restart the system.
Power grid operators and energy officials would effectively need to reboot the grid from scratch in a process called 'black start', says Owens.
Only a few power stations can carry out a black start, most are old, coal-fired plants that could slowly produce enough power to restart the network.
National Grid, which owns the high-voltage electricity grid in England and Wales, says this could be used to restore 60% of regional demand within 24 hours or so.
'This could take five to seven days for power to be completely restored, although the majority of customers would probably be restored within 24 hours,' adds Owens.
Power outages can also impact the local water supply to people's homes. Like electricity, getting water to people's homes involves a network of treatment plants, pumping stations and distribution systems that all require electricity.
If you're at all worried about the power cut in Spain and Portugal spilling out into the UK, don't be, stressed the National Energy System Operator, or NESO.
'Great Britain's electricity network was not affected by the power system incident on the European electricity network earlier today,' the body, which oversees British electricity and gas networks, tells Metro. More Trending
We are working closely with our counterparts across Europe to understand the cause of today's power system incident and to offer our support. It is too early to comment further on today's events and whilst investigations are still ongoing.'
Energy officials – and both experts Metro spoke with – have long stressed that Britain has among the most 'resislent' energy grids in the world.
But power cuts can do more than just turn out the lights.
'We've never been as reliant on the internet and interconnectivity,' Owens adds, 'but without electricity to power this digital world, our whole way of life quickly falls apart.'
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