In 2024/25 the average Great Britain interruption lasted about 88 minutes (35.1 minutes lost per customer divided by 0.397 interruptions a year). Unplanned cuts averaged between 59 and 112 minutes depending on the network; planned outages, which are notified in advance, averaged roughly 2 to 5 hours. Running the essentials at about 545 W for 88 minutes takes 0.8 kWh, so a 5 kWh battery with home battery backup covers an ordinary cut many times over. Storms are the exception, and Ofgem's figures largely leave them out.
Analysis · Published by SEO Dons Ltd · Updated 14 October 2026
Two numbers that make a third
Ofgem’s annual report on the electricity networks uses two measures for every distribution licence area:
- Customer interruptions (CI): the average number of supply interruptions per 100 customers in the year.
- Customer minutes lost (CML): the average time customers spent without power, in minutes per customer.
Neither says how long a cut lasts. But CML divided by (CI divided by 100) does: it is total minutes without power divided by the number of interruptions. For Great Britain in 2024/25 that is 35.11 divided by 0.3971, which is 88 minutes. For 2023/24 it is 36.67 divided by 0.4248, about 86 minutes. The figure is a derived average, not something Ofgem reports, and it covers every interruption a network counted, planned work included.
That one number answers the question most backup buyers actually have. A battery that covers 88 minutes of the essentials needs under a kilowatt-hour.
Unplanned and planned are different animals
Ofgem splits the figures, which lets the same sum be run separately. Unplanned interruptions (faults, trees, vehicles hitting poles) are shorter. Planned ones (a network operator isolating a line to work on it) are rarer but longer, and come with notice.
| Network area | Unplanned interruptions per 100 customers | Average unplanned length | Planned interruptions per 100 customers | Average planned length |
|---|---|---|---|---|
| South Wales | 38.1 | 59 minutes | 4.1 | 121 minutes |
| Eastern England | 43.3 | 68 minutes | 1.4 | 235 minutes |
| West Midlands | 43.8 | 68 minutes | 2.5 | 177 minutes |
| South Eastern England | 41.2 | 68 minutes | 1.0 | 237 minutes |
| East Midlands | 33.5 | 69 minutes | 0.8 | 173 minutes |
| South Western England | 55.1 | 76 minutes | 3.9 | 218 minutes |
| Southern Scotland | 30.4 | 77 minutes | 0.9 | 248 minutes |
| North Eastern England | 49.1 | 87 minutes | 2.0 | 216 minutes |
| Yorkshire | 53.0 | 90 minutes | 1.7 | 220 minutes |
| London | 11.2 | 93 minutes | under 0.1 | not meaningful |
| North Western England | 24.3 | 95 minutes | 1.8 | 223 minutes |
| Northern Scotland | 52.4 | 100 minutes | 6.7 | 246 minutes |
| Cheshire, Merseyside and Northern Wales | 26.8 | 109 minutes | 1.8 | 295 minutes |
| Southern England | 38.9 | 112 minutes | 3.0 | 264 minutes |
Two things stand out. Unplanned cuts averaged between 59 and 112 minutes in every area, and the networks with the most cuts are not always the ones with the longest ones: South Western England had a lot of interruptions (55 per 100 customers) but fixed them in about 76 minutes, while Southern England had fewer but longer ones. And planned outages are a different category: a typical one runs roughly three to five hours in most areas, which is long enough to matter for someone working from home or on medical equipment, and short enough that a full battery covers the essentials.
What the statistics leave out
Ofgem’s figures for the 14 areas are after “severe weather exceptional event” adjustments, which means the worst storms are largely taken out. They describe ordinary years. Backup is often bought for the other kind.
Two public records show how much the adjustment hides:
- Storm Eowyn, January 2025. On the evening of Saturday 25 January, the day after the storm, SSEN Distribution said more than 78,000 of its customers had been reconnected, about 12,000 households were still off supply, and some customers in its red-warning area were expected to be without power until the Monday. Northern Scotland also loses the most minutes per customer in Ofgem’s 2024/25 figures (68.91), which is why backup matters more for home batteries in the north of Scotland.
- Storm Isha, January 2024, Northern Ireland. NIE Networks’ report for 2023/24 shows 82.5 customer minutes lost excluding severe weather and 132.1 including it, and gives the storm itself as 11.7 interruptions per 100 customers and 49.6 minutes lost. One storm added about 60% to the average customer’s year. (NIE Networks reports to its own regulator on slightly different definitions, so read the comparison as a scale, not a precise match to the GB table.) NIE Networks runs Northern Ireland’s network on its own rules, covered in battery storage in Northern Ireland.
What each case needs, in battery terms
Using about 545 W for the essentials (a router, four LED bulbs, a fridge-freezer, a television and a phone charger, each at the top of its typical rating in National Energy Action’s table), the energy needed is:
| Situation | Duration | Energy for the essentials | Smallest sensible battery |
|---|---|---|---|
| Average GB interruption | 88 minutes | 0.8 kWh | Any home battery with backup |
| A bad unplanned cut | 3 hours | 1.6 kWh | A 5 kWh battery |
| A planned outage | 4 hours | 2.2 kWh | A 5 kWh battery, full beforehand |
| One day | 24 hours | 13 kWh | 13.5 kWh, or 10 kWh plus a solar recharge |
| A storm outage of three days | 72 hours | 39 kWh | Beyond one battery without solar |
The first three rows are covered by almost any battery that has backup; what differs is the hardware and its power limit rather than the capacity. The last two are where size and solar matter, and where solar recharging matters more than the battery’s size.
What to do with this
- Decide whether you need backup at all. If nobody depends on electric equipment and your area has average cuts, the insurance value is modest. The home battery backup page lists what the hardware costs and what it keeps on.
- If you do, prefer a backup circuit for the essentials. It keeps the draw low, so the energy stretches. Whole-home backup is easier to use but drains faster.
- Check the power limit as well as the capacity. A 5 kWh battery with a 3 kW limit cannot run a shower, however full it is.
- If outages in your area run long, size up and add solar. Panels that can recharge the battery during a cut turn hours into days. Compare quotes for the same backup spec with the battery storage quote form.
Questions people ask
How long does the average UK power cut last?
About 88 minutes across Great Britain in 2024/25, found by dividing Ofgem's 35.1 minutes lost per customer by its 39.7 interruptions per 100 customers. The same sum gives about 86 minutes for 2023/24, so the figure is stable year to year. Unplanned interruptions are shorter than planned ones, and individual networks range from about an hour to two hours.
How often do UK homes lose power?
On average once every 2.5 years in Great Britain, from Ofgem's 2024/25 figure of 39.7 interruptions per 100 customers. That ranges from once every nine years in London to once every 1.7 years in North Scotland and the South West. Storms that Ofgem treats as exceptional are largely excluded, so a stormy year can be worse.
How long do planned power cuts last?
Ofgem's planned-outage figures for 2024/25 work out at about two to five hours per interruption in most network areas, with Cheshire, Merseyside and North Wales the longest at about five hours. Planned outages come with notice from the network operator, so a battery can be full beforehand.
How much battery do I need for a power cut?
For the essentials (router, lights, a fridge-freezer, a television and phone charging, about 545 W at the top of typical ratings), an average 88-minute cut needs about 0.8 kWh and a four-hour planned outage about 2.2 kWh. A full day needs about 13 kWh and three days about 39 kWh, which is where one battery stops being enough without solar recharging it.
Do storms make power cuts much longer?
Yes, and the headline statistics hide it. After Storm Eowyn in January 2025, SSEN reported some customers in its red-warning area off supply until the following Monday. In Northern Ireland one storm in January 2024 added about 50 minutes to the average customer's year, against 82.5 minutes lost without storms.