Rolling blackout

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A rolling blackout, also referred to as rota or rotational load shedding, rota disconnection, feeder rotation, or a rotating outage, is an intentionally engineered electrical power shutdown in which electricity delivery is stopped for non-overlapping periods of time over different parts of the distribution region. Rolling blackouts are a last-resort measure used by an electric utility company to avoid a total blackout of the power system.

Rolling blackouts are a measure of demand response if the demand for electricity exceeds the power supply capability of the network. Rolling blackouts may be localised to a specific part of the electricity network, or they may be more widespread and affect entire countries and continents. Rolling blackouts generally result from two causes: insufficient generation capacity or inadequate transmission infrastructure to deliver power to where it is needed.

Rolling blackouts are also used as a response strategy to cope with reduced output beyond reserve capacity from power stations taken offline unexpectedly, such as an extreme weather event.

In developing countries[edit]

Rolling blackouts are a common or even a normal daily event in many developing countries,[1] where electricity generation capacity is underfunded or infrastructure is poorly managed. In well managed under-capacity systems, blackouts are scheduled in advance and advertised to allow people to work around them, but in most cases they happen without warning, typically whenever the transmission frequency falls below the 'safe' limit.

These have wide-ranging impacts, and can effect the expectations of communities – for example - in Ghana dumsor describes the widespread expectations for intermittent unexpected power outages due to rolling blackouts.

South Africa[edit]

Since 2007 South Africa has experienced multiple periods of rolling blackouts which are locally referred to as load shedding by the government owned energy utility Eskom. This was initially caused by the country's demand for electricity outgrowing its capacity to supply it and was later exacerbated by aging power infrastructure, poor maintenance and the slow completion of new power plants. This has caused significant damage to the South African economy and limited the country's economic growth.

In developed countries[edit]

Rolling blackouts in developed countries sometimes occur due to economic forces at the expense of system reliability (such as in the 2000–01 California energy crisis),[2][3] or during natural disasters such as heat waves.[4] In California rolling blackouts occurred in June 2000 and in January, March and May of 2001.[5] The 2021 Texas power crisis involved rolling blackouts caused by the February 13-17, 2021 North American winter storm and lack of winterization.[6]

2011 Tōhoku earthquake[edit]

After the 2011 Tōhoku earthquake and tsunami, Tokyo Electric Power Company implemented rolling blackouts. Its service area were divided to five blocks and blackouts were implemented from 6:20 to 22:00. The schedule from 15 to 18 March 2011 was as follows:[7][8]

Time 15 March 16 March 17 March 18 March
6:20–10:00 Block 3 Block 4 Block 5 Block 1
9:20–13:00 Block 4 Block 5 Block 1 Block 2
12:20–16:00 Block 5 Block 1 Block 2 Block 3
15:20–19:00 Block 1 Block 2 Block 3 Block 4
18:20–22:00 Block 2 Block 3 Block 4 Block 5


Intermittent access to electricity causes major economic problems for businesses, which incur costs in the form of lost resources, reduced patronage, or curtailed production if electrical equipment—for example refrigeration, lighting, or machinery—abruptly stops working.[9] Businesses in areas that are subject to regular blackouts may invest in backup power generation to avoid these costs, but power backup is itself a cost because generators must be purchased and maintained and fuel must be regularly replenished.


  1. ^ Agarwal, Anshul; Khandeparkar, Kedar (June 2021). "Distributing power limits: Mitigating blackout through brownout". Sustainable Energy, Grids and Networks. 26. doi:10.1016/j.segan.2021.100451. Retrieved 14 June 2022.
  2. ^ Bonsor, Kevin (2001). "How California's Power Crisis Works". HowStuffWorks.
  3. ^ "The California Crisis". Frontline.
  4. ^ Harvy, Ben; Shepherd, Tory (8 February 2017). "Rolling Blackouts Ordered as Adelaide Swelters in Heatwave".
  5. ^ Brown, Marilyn A. (2004). "Obstacles to Energy Efficiency". Encyclopedia of Energy. Elsevier Inc. Retrieved 14 June 2022.
  6. ^ Walsh, Dominic Anthony (16 February 2021). "What's Happening in Texas With the State's Power Grid". NPR.
  7. ^ "Implementation Plan of Rolling Blackout on and After Tue, March 15, 2011" (Press release). Tokyo Electric Power Company. 14 March 2011.
  8. ^ "Shūkan Keikaku Teishi Imēji" 週間計画停止イメージ [Weekly Planned Outage Image] (PDF) (in Japanese). Tokyo Electric Power Company.
  9. ^ McDonnell, Tim (24 November 2019). "The Powerlessness of Nigeria's Tech Startups". NPR.