Power cut guide
Why Do Power Cuts Happen? Common Causes in the UK
Quick answer: Most UK power cuts start on the local network, not the national grid. The usual causes are storms and lightning, trees and branches hitting overhead lines, underground cables damaged by digging or simply wearing out, faulty equipment in substations, animals such as birds and squirrels, and planned maintenance. Large cuts caused by problems on the national transmission system are rare.
Is the power off where you are? See live power cuts from the network operators and reports from neighbours.
When the lights go out, it helps to know what’s likely to have happened and why some cuts are fixed in minutes while others take hours. This guide explains the common causes in plain English, then shows how electricity gets from a power station to your plug, so the messages you get from your network operator make more sense. Links throughout lead to our more detailed guides on each topic.
How electricity reaches your home
It’s easier to understand what goes wrong once you know the basic layout. Think of the network as a set of roads: motorways for moving huge amounts of power long distances, then A-roads, then the residential street that ends at your front door.
Transmission: the motorways
Big power stations and offshore wind farms feed into the transmission network. In England and Wales it runs at 400,000 volts (400kV) and 275kV, carried mostly on the tall steel pylons you see crossing the countryside. In Scotland, the transmission network also includes lower-voltage lines down to 132kV. The National Energy System Operator (NESO) balances supply and demand across Great Britain second by second.
Distribution: the local roads
At large substations, transformers step the voltage down and pass the electricity to a distribution network operator (DNO). The DNO’s network carries it at up to 132kV, then lower “high voltage” (HV) levels such as 33kV and 11kV, along wooden poles or underground cables. Finally, a local substation, often a small fenced box or kiosk in a street, steps it down to “low voltage” (LV): the 230 volts that comes out of your sockets.
| Part of the network | Typical voltage | What a fault here usually means |
|---|---|---|
| Transmission (pylons, big substations) | 400kV and 275kV (plus 132kV in Scotland) | Rare, but can affect very large areas |
| Distribution, high voltage | 132kV down to 11kV | Can cut off a town, several villages or thousands of homes |
| Local substation and low-voltage cables | 230V (single-phase home supply) | Affects one street, a few streets, or a block of flats |
| Your service cable and main fuse | 230V | Only your property |
Great Britain’s local networks are split into 14 areas run by six companies, and Northern Ireland has its own. Our guide to the UK’s electricity network operators shows who covers your area.
Weather and trees
Bad weather is behind many of the biggest and longest power cuts, because it causes lots of faults at once over a wide area.
- Strong wind brings down branches and whole trees onto overhead lines, and can blow debris such as trampolines or roofing into them.
- Lightning can strike lines and equipment directly. Protection equipment often trips the line to clear the fault, which can cause a flicker or short cut.
- Snow and ice add weight to lines and branches until something snaps.
- Flooding can damage substations and underground equipment. Operators may also switch off a substation deliberately before water reaches it, to protect it.
- Hot spells can put extra strain on some equipment.
Rural homes on long overhead lines tend to feel storms the most. If you live somewhere exposed, our guide to preparing for storm season power cuts has a checklist to work through before a named storm.
Trees and vegetation
Trees don’t need a storm to cause trouble. A branch that has grown too close to an overhead line can touch it on a breezy day, or during wet weather when leaves are heavy. Network operators run tree-cutting programmes for this reason.
If you see a tree growing into a line, report it to your network operator rather than cutting it yourself. Electricity can jump from a line to a branch, a ladder or a tool, so trimming near lines is work for trained teams only.
Damage by people: digging, vehicles, theft and vandalism
Underground cables are often damaged by work going on above them. Builders, utility contractors and householders can strike buried cables with diggers, drills or even a garden fork driven in hard. Vehicles hitting poles, overhead lines snagged by tall farm machinery or lorries, and kites or drones caught in wires all cause cuts too.
Theft and vandalism of copper cable and substation equipment is another cause network operators highlight. It’s dangerous for the people involved and can leave whole streets without power.
Safety: If you’re planning to dig deeper than ordinary gardening, ask your network operator for plans of underground cables first. If you hit a cable, step away, don’t touch it or the tool, keep others back and call 105. If anyone is hurt or there’s fire, call 999.
Equipment faults, wear and animals
Some cuts happen with no outside cause at all. Underground cables, joints, transformers and switchgear age, and insulation can break down. A fault might show up as a single short interruption, then come back days later until engineers find and replace the damaged section.
Substation fires are uncommon but can be serious. In March 2025, a fire at the North Hyde substation in west London, which supplied the area around Heathrow, cut power to more than 71,000 homes and businesses and closed the airport for most of the following day. The official review found it was most likely caused by moisture getting into part of a transformer, and made recommendations on maintenance and fire risk.
Why the lights sometimes flicker or go off briefly
The network has automatic protection that switches off a faulty section in a fraction of a second, then often tries to switch it back on. If the fault was temporary, such as a branch brushing a line, you may notice a flicker or a cut of a few seconds. Network operators class cuts under three minutes as short interruptions. If the fault is still there, the protection stays off and you get a longer cut while engineers investigate.
Animals
Birds landing on equipment, squirrels climbing into substations and other wildlife can bridge two parts of the network that should never touch. The result is usually a sudden fault that trips the supply to a local area. These cuts are often fixed quickly once engineers find the cause.
Faults inside your own home
Not every power cut is the network’s fault. If only your house is off, a faulty appliance or circuit may have tripped your consumer unit, or the operator’s main fuse in your meter cupboard may have failed. The quickest way to tell is to check your trip switches and look at whether neighbours have lights.
A prepayment meter that has run out of credit, or a smart meter showing an error, can also look like a power cut. Low carbon kit can surprise people too: solar panels and most home batteries are designed to switch themselves off when the grid fails, so they won’t keep your lights on unless they have a backup function.
Planned power cuts
Some power cuts are deliberate. Network operators sometimes need to switch off part of the network to connect new homes, replace old equipment, cut back trees or carry out maintenance safely. In Great Britain, they must give you at least two calendar days’ notice, and you may be due a payment if they don’t.
You can check planned power cuts for your area on our site. Our guide to planned power cuts explains why they happen and what you’re entitled to.
National grid-level events: rare but possible
Problems on the transmission system that cut off large numbers of people are unusual. One of the best-known recent examples happened on 9 August 2019. A lightning strike on a 400kV line was cleared within a fraction of a second, but two large generators then tripped off at almost the same time, along with smaller ones. To protect the rest of the system, around 1.15 million customers were disconnected automatically. Power was back for all of them within about 45 minutes, though rail services were badly disrupted for longer.
Ofgem’s report on that event noted that Great Britain has relatively few outages of this kind affecting consumers. For most households, the chance of a cut on any given day depends far more on local factors such as overhead lines, trees and the age of nearby cables.
Why some power cuts last longer than others
Several things affect how quickly power comes back:
- Where the fault is. Engineers can often switch supplies around a faulty high-voltage cable remotely, restoring many homes before the actual repair.
- Underground or overhead. Underground cable faults need locating and digging out, which takes time.
- The weather. In big storms there may be hundreds of faults at once, and some repairs can’t start until winds drop.
- Access. Remote or island locations, flooded roads and fallen trees slow crews down.
Our guide to how long power cuts last covers typical timings and what estimated restoration times mean.
If you live in Northern Ireland, things work a little differently: see our guide to power cuts in Northern Ireland. If you work from home, read about protecting your devices and work in a power cut.
Frequently asked questions
What is the most common cause of power cuts in the UK?
It varies by area and by year. Weather and trees cause many cuts on overhead lines, especially in rural areas, while damage from digging and ageing equipment are big causes on underground networks in towns and cities. Your network operator can tell you what caused a particular cut.
Why does my power keep going off for a few seconds?
Brief cuts usually happen when automatic protection switches off a faulty section of line and then switches it back on. Repeated short cuts can point to a developing fault, so report them on 105 even if the power comes straight back.
Is a power cut the same as a national grid failure?
Almost never. The vast majority of cuts are on the local distribution network run by your network operator. Large events on the national transmission system are rare.
Who fixes power cuts, my supplier or someone else?
Your network operator owns and repairs the cables and substations. Your energy supplier sends your bills but doesn’t fix power cuts, so call 105 (or NIE Networks in Northern Ireland) rather than your supplier. Our guide to network operators and energy suppliers explains who does what.
If your power is off right now, see today’s power cuts or check your postcode to find out whether your network operator already knows about it and when it expects the supply to be back.
Sources
- Electricity North West u2013 Why power cuts happen
- National Grid u2013 Electricity transmission vs electricity distribution
- SSEN Transmission u2013 What we do
- Ofgem u2013 9 August 2019 power outage report (PDF)
- NESO u2013 Final report of the review into the North Hyde substation outage
- UK Power Networks u2013 Power cuts and your low carbon technologies
Checked against these sources on 28 October 2026. Rules and amounts can change – your network operator or Ofgem has the final word. Spotted something out of date? Tell us.