{ "meta": { "title": "Power cuts in Great Britain: how often the lights go out, and for how long", "standfirst": "In 2024/25 the average electricity customer in Great Britain lost 35.1 minutes of supply and saw 39.7 interruptions per 100 customers, both slightly better than the year before. The average hides a 6.6 times gap between the best and worst served licence areas: 10.5 minutes in UKPN London against 68.9 in SSEN Scottish Hydro. 11 of the 14 areas missed their duration target and the network companies paid \u00a350.9m in penalties over two years. This page puts Ofgem's reliability figures beside the Government's advice to prepare for outages of several days.", "sourceNote": "Computed from Ofgem's RIIO-2 Electricity Distribution annual report 2024 to 2025 supplementary data file (published January 2026), Chapter 2 reliability outputs: Customer Interruptions and Customer Minutes Lost by licence area for 2023/24 and 2024/25, with targets, RAG status and Interruptions Incentive Scheme rewards. Customer numbers are the 2025 figures from the same workbook. Group rewards and the \u00a350.9m cumulative penalty are asserted at build time against Table 6 and the text of the report. Winter margins are NESO's, quoted with their date.", "basis": "Two regulatory averages per licence area, planned and unplanned interruptions of three minutes or more, adjusted for severe weather. Customer Minutes Lost is spread across every customer, so it is a measure of the network, not of what a household that lost power experienced. Rewards and penalties are adjustments to the revenue a company may recover through bills. The national winter margin is NESO's separate question of whether generation can meet peak demand, and is quoted, not computed.", "period": "2024/25", "published": "January 2026", "sectorCml": "35.1", "sectorCi": "39.7", "penaltyTotal": "\u00a350.9m", "areasMissedCml": 11, "customersTotal": 30424804 }, "headline": { "eyebrow": "The two numbers Ofgem regulates", "heading": "35.1 minutes a year without power, on average", "intro": "Ofgem sets every distribution network two reliability targets. Customer Interruptions (CI) is the average number of supply interruptions per 100 customers in a year. Customer Minutes Lost (CML) is the average number of minutes each customer is without supply in a year, averaged across every customer, including the majority who had no cut at all. Both cover planned and unplanned interruptions of three minutes or longer, and both are adjusted for severe weather events before Ofgem's final assessment. In 2024/25 the sector figure for CML was 35.1 minutes, down from 36.7 in 2023/24, and CI was 39.7 per 100 customers, down from 42.5. Ofgem's own reading is that performance improved on the first year of the price control but that several companies still missed deliberately demanding targets.", "sector": { "cml": { "2023/24": 36.67, "2024/25": 35.11 }, "ci": { "2023/24": 42.48, "2024/25": 39.71 } }, "definitions": [ { "term": "Customer Interruptions (CI)", "text": "The average number of supply interruptions per 100 customers. Ofgem's definition, annual report 2024-25." }, { "term": "Customer Minutes Lost (CML)", "text": "The average duration of interruptions experienced by customers, in minutes per customer per year. Ofgem's definition, annual report 2024-25." } ] }, "duration": { "eyebrow": "Minutes lost by licence area", "heading": "SSEN Scottish Hydro customers lost 6.6 times as many minutes as UKPN London customers", "intro": "Great Britain is served by 14 electricity distribution licence areas run by six groups. The bars are Customer Minutes Lost in 2024/25. SSEN Scottish Hydro, serving north of Scotland, recorded 68.9 minutes per customer against a target of 52.9. UKPN London, serving London, recorded 10.5. Rural areas with long overhead lines exposed to weather sit at the top; dense urban networks with underground cables sit at the bottom. Red marks an area Ofgem rated red against its target for the year.", "rows": [ { "code": "SSEH", "name": "SSEN Scottish Hydro", "group": "SSEN", "groupName": "Scottish and Southern Electricity Networks", "served": "north of Scotland", "customers": 797655, "cml": 68.91, "cmlPrev": 65.56, "cmlTarget": 52.87, "cmlRag": "Red", "ci": 59.1, "ciPrev": 56.64, "ciTarget": 61.89, "ciRag": "Green", "reward": -2.23, "rewardPrev": -1.57 }, { "code": "NPgY", "name": "Northern Powergrid Yorkshire", "group": "NPg", "groupName": "Northern Powergrid", "served": "Yorkshire", "customers": 2331593, "cml": 51.2, "cmlPrev": 53.49, "cmlTarget": 39.09, "cmlRag": "Red", "ci": 54.66, "ciPrev": 55.21, "ciTarget": 45.85, "ciRag": "Red", "reward": -6.65, "rewardPrev": -7.23 }, { "code": "SSES", "name": "SSEN Southern", "group": "SSEN", "groupName": "Scottish and Southern Electricity Networks", "served": "central southern England", "customers": 3150112, "cml": 51.18, "cmlPrev": 57.58, "cmlTarget": 41.65, "cmlRag": "Red", "ci": 41.85, "ciPrev": 51.27, "ciTarget": 46.06, "ciRag": "Green", "reward": -4.81, "rewardPrev": -9.37 }, { "code": "SWEST", "name": "NGED South West", "group": "NGED", "groupName": "National Grid Electricity Distribution", "served": "South West England", "customers": 1662078, "cml": 50.43, "cmlPrev": 46.86, "cmlTarget": 38.83, "cmlRag": "Red", "ci": 59.01, "ciPrev": 57.52, "ciTarget": 51.45, "ciRag": "Red", "reward": -4.38, "rewardPrev": -2.94 }, { "code": "NPgN", "name": "Northern Powergrid Northeast", "group": "NPg", "groupName": "Northern Powergrid", "served": "North East England", "customers": 1617948, "cml": 46.75, "cmlPrev": 49.48, "cmlTarget": 41.06, "cmlRag": "Red", "ci": 51.03, "ciPrev": 48.61, "ciTarget": 46.69, "ciRag": "Red", "reward": -2.31, "rewardPrev": -2.53 }, { "code": "SPMW", "name": "SP Manweb", "group": "SPEN", "groupName": "SP Energy Networks", "served": "Merseyside, Cheshire and North Wales", "customers": 1532350, "cml": 34.54, "cmlPrev": 33.43, "cmlTarget": 31.04, "cmlRag": "Red", "ci": 28.55, "ciPrev": 31.57, "ciTarget": 33.0, "ciRag": "Green", "reward": -0.6, "rewardPrev": -0.23 }, { "code": "WMID", "name": "NGED West Midlands", "group": "NGED", "groupName": "National Grid Electricity Distribution", "served": "West Midlands", "customers": 2526904, "cml": 34.18, "cmlPrev": 32.91, "cmlTarget": 29.54, "cmlRag": "Red", "ci": 46.31, "ciPrev": 44.75, "ciTarget": 47.88, "ciRag": "Green", "reward": -1.98, "rewardPrev": -0.78 }, { "code": "EPN", "name": "UKPN Eastern", "group": "UKPN", "groupName": "UK Power Networks", "served": "East of England", "customers": 3712071, "cml": 32.51, "cmlPrev": 35.6, "cmlTarget": 30.09, "cmlRag": "Red", "ci": 44.62, "ciPrev": 46.2, "ciTarget": 41.83, "ciRag": "Red", "reward": -2.4, "rewardPrev": -4.02 }, { "code": "SPN", "name": "UKPN South Eastern", "group": "UKPN", "groupName": "UK Power Networks", "served": "Kent, Sussex and Surrey", "customers": 2358803, "cml": 30.37, "cmlPrev": 36.49, "cmlTarget": 31.15, "cmlRag": "Green", "ci": 42.19, "ciPrev": 49.52, "ciTarget": 42.54, "ciRag": "Green", "reward": 0.29, "rewardPrev": -3.05 }, { "code": "SWALES", "name": "NGED South Wales", "group": "NGED", "groupName": "National Grid Electricity Distribution", "served": "South Wales", "customers": 1161671, "cml": 27.51, "cmlPrev": 26.1, "cmlTarget": 24.59, "cmlRag": "Red", "ci": 42.1, "ciPrev": 46.34, "ciTarget": 42.27, "ciRag": "Green", "reward": -0.63, "rewardPrev": -0.61 }, { "code": "SP ENW", "name": "Electricity North West", "group": "SP ENW", "groupName": "SP Electricity North West", "served": "North West England", "customers": 2430262, "cml": 27.09, "cmlPrev": 26.8, "cmlTarget": 26.87, "cmlRag": "Amber", "ci": 26.07, "ciPrev": 26.21, "ciTarget": 29.74, "ciRag": "Green", "reward": 0.43, "rewardPrev": 0.87 }, { "code": "SPD", "name": "SP Distribution", "group": "SPEN", "groupName": "SP Energy Networks", "served": "central and southern Scotland", "customers": 2017857, "cml": 25.76, "cmlPrev": 26.23, "cmlTarget": 29.56, "cmlRag": "Green", "ci": 31.29, "ciPrev": 32.88, "ciTarget": 41.76, "ciRag": "Green", "reward": 2.73, "rewardPrev": 2.96 }, { "code": "EMID", "name": "NGED East Midlands", "group": "NGED", "groupName": "National Grid Electricity Distribution", "served": "East Midlands", "customers": 2705005, "cml": 24.61, "cmlPrev": 26.14, "cmlTarget": 22.71, "cmlRag": "Red", "ci": 34.31, "ciPrev": 44.2, "ciTarget": 38.5, "ciRag": "Green", "reward": -0.29, "rewardPrev": -2.42 }, { "code": "LPN", "name": "UKPN London", "group": "UKPN", "groupName": "UK Power Networks", "served": "London", "customers": 2420495, "cml": 10.46, "cmlPrev": 11.37, "cmlTarget": 13.56, "cmlRag": "Green", "ci": 11.2, "ciPrev": 12.2, "ciTarget": 13.39, "ciRag": "Green", "reward": 1.68, "rewardPrev": 1.19 } ], "note": "Customer Minutes Lost, planned and unplanned, 2024/25, with Ofgem's RAG rating against the area's target. Customer numbers are 2025. Source: Ofgem supplementary data file, Chapter 2 reliability outputs." }, "frequency": { "eyebrow": "Interruptions by licence area", "heading": "SSEN Scottish Hydro customers were interrupted most often", "intro": "Customer Interruptions counts how often supply is lost rather than for how long. In 2024/25 the range ran from 59.1 interruptions per 100 customers in SSEN Scottish Hydro to 11.2 in UKPN London. 4 of the 14 areas were above their CI target and 10 improved on 2023/24.", "rows": [ { "code": "SSEH", "name": "SSEN Scottish Hydro", "ci": 59.1, "ciTarget": 61.89, "ciRag": "Green" }, { "code": "SWEST", "name": "NGED South West", "ci": 59.01, "ciTarget": 51.45, "ciRag": "Red" }, { "code": "NPgY", "name": "Northern Powergrid Yorkshire", "ci": 54.66, "ciTarget": 45.85, "ciRag": "Red" }, { "code": "NPgN", "name": "Northern Powergrid Northeast", "ci": 51.03, "ciTarget": 46.69, "ciRag": "Red" }, { "code": "WMID", "name": "NGED West Midlands", "ci": 46.31, "ciTarget": 47.88, "ciRag": "Green" }, { "code": "EPN", "name": "UKPN Eastern", "ci": 44.62, "ciTarget": 41.83, "ciRag": "Red" }, { "code": "SPN", "name": "UKPN South Eastern", "ci": 42.19, "ciTarget": 42.54, "ciRag": "Green" }, { "code": "SWALES", "name": "NGED South Wales", "ci": 42.1, "ciTarget": 42.27, "ciRag": "Green" }, { "code": "SSES", "name": "SSEN Southern", "ci": 41.85, "ciTarget": 46.06, "ciRag": "Green" }, { "code": "EMID", "name": "NGED East Midlands", "ci": 34.31, "ciTarget": 38.5, "ciRag": "Green" }, { "code": "SPD", "name": "SP Distribution", "ci": 31.29, "ciTarget": 41.76, "ciRag": "Green" }, { "code": "SPMW", "name": "SP Manweb", "ci": 28.55, "ciTarget": 33.0, "ciRag": "Green" }, { "code": "SP ENW", "name": "Electricity North West", "ci": 26.07, "ciTarget": 29.74, "ciRag": "Green" }, { "code": "LPN", "name": "UKPN London", "ci": 11.2, "ciTarget": 13.39, "ciRag": "Green" } ], "note": "Customer Interruptions per 100 customers, planned and unplanned, 2024/25. Source: Ofgem supplementary data file." }, "money": { "eyebrow": "Rewards and penalties", "heading": "\u00a350.9m in net penalties over the first two years of the price control", "intro": "Under the Interruptions Incentive Scheme a company that beats its targets earns a reward on its allowed revenue and one that misses them pays a penalty, capped at 150 basis points of return on regulatory equity. In 2024/25 4 of the 14 areas earned a reward and 10 paid a penalty. By group, SP Energy Networks earned \u00a32.1m and Northern Powergrid paid \u00a39.0m. Over 2023/24 and 2024/25 together the net position across all six groups is a penalty of \u00a350.9m, the figure Ofgem's report describes as cumulative penalties to date. Penalties are a transfer back to customers through allowed revenue, not a fine paid to the Treasury.", "groups": [ { "code": "SPEN", "name": "SP Energy Networks", "areas": [ "SP Distribution", "SP Manweb" ], "reward": 2.12, "cumulative": 4.85, "customers": 3550207 }, { "code": "SP ENW", "name": "SP Electricity North West", "areas": [ "Electricity North West" ], "reward": 0.43, "cumulative": 1.3, "customers": 2430262 }, { "code": "UKPN", "name": "UK Power Networks", "areas": [ "UKPN London", "UKPN South Eastern", "UKPN Eastern" ], "reward": -0.43, "cumulative": -6.32, "customers": 8491369 }, { "code": "SSEN", "name": "Scottish and Southern Electricity Networks", "areas": [ "SSEN Scottish Hydro", "SSEN Southern" ], "reward": -7.05, "cumulative": -17.98, "customers": 3947767 }, { "code": "NGED", "name": "National Grid Electricity Distribution", "areas": [ "NGED West Midlands", "NGED East Midlands", "NGED South Wales", "NGED South West" ], "reward": -7.27, "cumulative": -14.02, "customers": 8055658 }, { "code": "NPg", "name": "Northern Powergrid", "areas": [ "Northern Powergrid Northeast", "Northern Powergrid Yorkshire" ], "reward": -8.96, "cumulative": -18.72, "customers": 3949541 } ], "note": "Interruptions Incentive Scheme total reward or penalty, \u00a3m, by group, 2024/25 and cumulative 2023/24 to 2024/25. Reconciled to Table 6 of Ofgem's annual report. Source: Ofgem supplementary data file." }, "trend": { "eyebrow": "Direction of travel", "heading": "8 of 14 areas cut minutes lost on the year", "intro": "Between 2023/24 and 2024/25 the sector figure for minutes lost fell from 36.7 to 35.1 and interruptions per 100 customers fell from 42.5 to 39.7. 8 areas improved on duration and 10 on frequency. The longer record is Ofgem's: its RIIO-ED1 performance summary for 2021-22 reported that over the previous price control, from 2015-16, customer interruptions had fallen by 23 per cent and the duration of interruptions by 18 per cent, and that every licence area met its targets that year. The targets were then tightened for RIIO-ED2, which is why an industry that is more reliable than a decade ago is now paying penalties.", "rows": [ { "code": "SSES", "name": "SSEN Southern", "cmlPrev": 57.58, "cml": 51.18, "change": -6.4 }, { "code": "SPN", "name": "UKPN South Eastern", "cmlPrev": 36.49, "cml": 30.37, "change": -6.12 }, { "code": "EPN", "name": "UKPN Eastern", "cmlPrev": 35.6, "cml": 32.51, "change": -3.1 }, { "code": "NPgN", "name": "Northern Powergrid Northeast", "cmlPrev": 49.48, "cml": 46.75, "change": -2.73 }, { "code": "NPgY", "name": "Northern Powergrid Yorkshire", "cmlPrev": 53.49, "cml": 51.2, "change": -2.29 }, { "code": "EMID", "name": "NGED East Midlands", "cmlPrev": 26.14, "cml": 24.61, "change": -1.53 }, { "code": "LPN", "name": "UKPN London", "cmlPrev": 11.37, "cml": 10.46, "change": -0.91 }, { "code": "SPD", "name": "SP Distribution", "cmlPrev": 26.23, "cml": 25.76, "change": -0.47 }, { "code": "SP ENW", "name": "Electricity North West", "cmlPrev": 26.8, "cml": 27.09, "change": 0.29 }, { "code": "SPMW", "name": "SP Manweb", "cmlPrev": 33.43, "cml": 34.54, "change": 1.11 }, { "code": "WMID", "name": "NGED West Midlands", "cmlPrev": 32.91, "cml": 34.18, "change": 1.26 }, { "code": "SWALES", "name": "NGED South Wales", "cmlPrev": 26.1, "cml": 27.51, "change": 1.41 }, { "code": "SSEH", "name": "SSEN Scottish Hydro", "cmlPrev": 65.56, "cml": 68.91, "change": 3.35 }, { "code": "SWEST", "name": "NGED South West", "cmlPrev": 46.86, "cml": 50.43, "change": 3.57 } ], "ed1": { "ciFallPct": 23, "cmlFallPct": 18, "from": "2015-16", "to": "2021-22", "quote": "Over RIIO-ED1 to date, customer interruptions have fallen by 23% whilst the duration of interruptions has reduced by 18%.", "source": "Ofgem, RIIO-ED1 Network Performance Summary 2021-22", "url": "https://www.ofgem.gov.uk/sites/default/files/2023-03/RIIO-ED1%20Network%20Performance%20Summary%202021-22.pdf" } }, "winter": { "eyebrow": "The national picture", "heading": "The grid has a margin this winter. The Government still says prepare for days without power", "intro": "Local cuts are about wires and weather. A national shortage is a different risk, and the National Energy System Operator publishes its expectation every autumn. Its Winter Outlook for 2025/26, published 9 October 2025, forecast an operational margin of 6.1 GW, the highest since 2019/20 and about 10 per cent of average peak demand, while cautioning that some tighter periods might still occur. For the coming winter NESO's early view, published 23 June 2026, expects a surplus of 5.5 GW between 31 October 2026 and 31 March 2027, an 8.8 per cent buffer over expected peak demand, with January the month it names as most likely to be finely balanced. The full outlook is due in October and this page will be refreshed when it lands. Alongside that, the Cabinet Office's Prepare campaign says most power cuts are short and local but that longer outages could last several days with regional or, although unlikely, national impacts, and tells households to keep a battery or wind up torch and radio, bottled water and food that needs no cooking, to know the 105 number for reporting a cut, and to find their load block letter, the rota under which areas would be disconnected for around three hours at a time in a national shortage.", "neso": { "outlook2526": { "marginGw": 6.1, "sharePct": 10, "published": "9 October 2025", "url": "https://www.neso.energy/neso-sets-out-expectations-strongest-winter-electricity-margins-six-years", "quote": "forecasts electricity margins of 6.1GW, the highest since 2019/20 and equivalent to 10% of average peak demand" }, "earlyView2627": { "marginGw": 5.5, "sharePct": 8.8, "published": "23 June 2026", "url": "https://www.neso.energy/publications/winter-watch", "quote": "We expect a surplus of 5.5GW between 31 October 2026 and 31 March 2027, with an 8.8% buffer over expected peak demand." }, "outlookPage": "https://www.neso.energy/publications/winter-outlook" }, "prepare": { "url": "https://prepare.campaign.gov.uk/be-informed-about-hazards/power-cuts/", "items": [ "Keep a battery or wind up torch and spare batteries; torches are safer than candles.", "Keep bottled water and food that does not need cooking, with a tin opener.", "Keep a battery or wind up radio; updates may come by radio during a cut.", "Write down 105, the number to report a power cut in England, Scotland and Wales.", "Find your load block letter at powercut105.com; in a national shortage areas would be disconnected in turn for around three hours at a time.", "If eligible, join your supplier's Priority Services Register." ], "quote": "Most power cuts are short-lived and occur locally, but more widespread and longer outages can happen. These could potentially last several days with regional or, although unlikely, national impacts." } }, "questions": { "eyebrow": "Questions this raises", "heading": "What the figures do not settle", "items": [ { "q": "Is 35 minutes a year a lot?", "a": "It is an average across 30.4 million customers, most of whom had no interruption at all in the year. A household that did lose supply typically lost far more than 35 minutes; the measure spreads every outage across everyone. Ofgem publishes no distribution of outage lengths by household, so the page cannot say how many customers went a day or more without power." }, { "q": "Why are the targets missed if reliability is improving?", "a": "Because RIIO-ED2 targets were set to keep tightening. Ofgem's report says the targets were deliberately challenging and that most companies improved between the first and second years even where they missed. A penalty under the scheme means an area fell short of its own target, not that it got worse." }, { "q": "Do the penalties come back to customers?", "a": "They reduce the revenue the company is allowed to recover through network charges on bills in later years. They are not a fine paid to government. The scheme also pays rewards to companies that beat targets, so the net \u00a350.9m over two years is the balance of both." }, { "q": "What about a national power cut?", "a": "NESO's outlook measures whether generation can meet peak demand with reserves to spare; the local reliability figures measure faults on the wires. Great Britain has not had a rota disconnection since the 1970s. The Prepare campaign's load block letters describe the arrangement that would apply if one were ever needed." }, { "q": "When is the next data?", "a": "Ofgem's next annual report, covering 2025-26, is due around the turn of the year. NESO's full Winter Outlook for 2026/27 is due in October 2026. Both will be read into this page when they are published." } ] }, "sources": [ { "name": "Ofgem, RIIO-2 Electricity Distribution: annual report 2024 to 2025 (supplementary data file)", "licence": "Open Government Licence v3.0", "url": "https://www.ofgem.gov.uk/transparency-document/riio-2-electricity-distribution-annual-report-2024-2025", "note": "Chapter 2 reliability outputs: CI, CML, targets, RAG, IIS rewards; Guide and drivers: customer numbers." }, { "name": "Ofgem, RIIO-2 Electricity Distribution: annual report 2024 to 2025 (report)", "licence": "Open Government Licence v3.0", "url": "https://www.ofgem.gov.uk/sites/default/files/2026-01/ED-annual-report-2024-2025.pdf", "note": "Definitions of CI and CML, Table 6 group rewards, the \u00a350.9m cumulative penalty, and Ofgem's commentary." }, { "name": "Ofgem, RIIO-ED1 Network Performance Summary 2021-22", "licence": "Open Government Licence v3.0", "url": "https://www.ofgem.gov.uk/sites/default/files/2023-03/RIIO-ED1%20Network%20Performance%20Summary%202021-22.pdf", "note": "The 23 per cent and 18 per cent falls over 2015-16 to 2021-22, quoted as Ofgem states them." }, { "name": "NESO, Winter Outlook 2025/26 press release, 9 October 2025", "licence": "NESO open data, attributed", "url": "https://www.neso.energy/neso-sets-out-expectations-strongest-winter-electricity-margins-six-years", "note": "The 6.1 GW operational margin and the 10 per cent of average peak demand." }, { "name": "NESO, Winter Watch: early view of winter 2026/27", "licence": "NESO open data, attributed", "url": "https://www.neso.energy/publications/winter-watch", "note": "The 5.5 GW surplus and 8.8 per cent buffer for 31 October 2026 to 31 March 2027, in NESO's words." }, { "name": "NESO, Winter Outlook publications", "licence": "NESO open data, attributed", "url": "https://www.neso.energy/publications/winter-outlook", "note": "Where the October 2026 outlook will be published." }, { "name": "Cabinet Office, Prepare campaign: power cuts", "licence": "Open Government Licence v3.0", "url": "https://prepare.campaign.gov.uk/be-informed-about-hazards/power-cuts/", "note": "The household advice quoted in the winter section." } ], "caveats": [ "CI and CML are Ofgem's regulatory measures for Great Britain's 14 distribution licence areas. Northern Ireland has a separate regulator and is not covered.", "Both measures exclude interruptions shorter than three minutes and are adjusted for severe weather exceptional events on the companies' submissions, before Ofgem's final assessment. Ofgem notes the adjustments will be confirmed after the report.", "CML is an average across all customers in an area, including those with no interruption, so it understates the length of a cut experienced by a household that had one.", "The licence area descriptions of the regions served are approximate; boundaries follow network geography, not local authority lines.", "Rewards and penalties are in \u00a3m as Ofgem reports them in the supplementary file, on a 2020/21 price base, and are adjustments to allowed revenue rather than fines.", "NESO's margins describe the national generation position, not local network reliability. The two are different risks and are not combined here." ] }