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Base load

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Some early nuclear plants, such as the VVER-440 (pictured at Metsamor) were designed for baseload operation [1]

The base load[2] (also baseload) is the minimum level of demand on an electrical grid over a span of time, for example, one week. This demand can be met by unvarying power plants,[3] dispatchable generation,[4] or by a collection of smaller intermittent energy sources,[5] depending on which approach has the best mix of cost, availability and reliability in any particular market. The remainder of demand, varying throughout a day, is met by dispatchable generation which can be turned up or down quickly, such as load following power plants, peaking power plants, or energy storage.

Power plants that do not change their power output quickly, such as some large coal or nuclear plants, are generally called baseload power plants.[3][6][7] In the 20th century most or all of base load demand was met with baseload power plants,[8] whereas new capacity based around renewables often employs flexible generation.[9]



Grid operators take long and short term bids to provide electricity over various time periods and balance supply and demand continuously.[10] The detailed adjustments are known as the unit commitment problem in electrical power production.[citation needed]

While historically large power grids used unvarying power plants to meet the base load, there is no specific technical requirement for this to be so. The base load can equally well be met by the appropriate quantity of intermittent power sources and dispatchable generation.[4][5]

Unvarying power plants can be coal, nuclear, combined cycle plants, which may take several days to start up and shut down,[11] hydroelectric, geothermal,[12] biogas, biomass, solar thermal with storage and ocean thermal energy conversion.

The desirable attribute of dispatchability applies to some gas plants and hydroelectricity. Grid operators also use curtailment to shut plants out of the grid when their energy is not needed.[13][14]


Grids with high penetration of renewable energy sources generally need more flexible generation rather than baseload generation

Grid operators solicit bids to find the cheapest sources of electricity over short and long term buying periods.[15]

Nuclear and coal plants have very high fixed costs, high plant load factor[16] but very low marginal costs.[citation needed] On the other hand, peak load generators, such as natural gas, have low fixed costs, low plant load factor and high marginal costs.[17]

Some coal and nuclear power plants do not change production to match power consumption demands since it is sometimes more economical to operate them at constant production levels, and not all power plants are designed for it. The IEA has suggested that coal power plants should not run as baseload, because that emits a lot of carbon dioxide, which causes climate change.[18] Some nuclear power stations, such as those in France, are physically capable of being used as load following power plants and do alter their output, to some degree, to help meet varying demands.[19][moved resource?][20][moved resource?]

Some combined-cycle plants usually fuelled by gas, can provide baseload power,[21][need quotation to verify][obsolete source]as well as being able to be cost-effectively cycled up and down to match more rapid fluctuations in consumption.

According to National Grid plc chief executive officer Steve Holliday in 2015, and others, baseload is "outdated".[9][7] By 2019, Steve Holliday had left his position as CEO of National Grid plc and went on the record to say that, "It’s hard to conceive that nuclear does not have an important role to play"[22]

See also



  1. ^ Szondy, Borbála; Bodnár, Balázs; Grossetête, Alain; Gain, Thibaut; Aszódi, Attila (2024). "Review of solutions developed for improving maneuvering flexibility in German, French and Russian PWRs targeting to explore future possibilities for the new VVER-1200 nuclear power plant units in Hungary". Nuclear Engineering and Design. 419. Bibcode:2024NuEnD.41912965S. doi:10.1016/j.nucengdes.2024.112965.
  2. ^ "Definition of "baseload"". www.merriam-webster.com. Merriam Webster Dictionary. Retrieved 2018-12-02.
  3. ^ a b Donald G. Fink, H. Wayne Beatty (ed), Standard Handbook for Electrical Engineers, Eleventh Edition, Mc-Graw Hill, 1978 ISBN 9780070209749, pp. 12-16 through 12-18
  4. ^ a b Peters, Roger, Cherise Burda (2007-09-01). "The Basics on Base Load: Meeting Ontario's Base Load Electricity Demand with Renewable Power Sources" (PDF). Pembina Institute. Retrieved 2018-05-16.{{cite web}}: CS1 maint: multiple names: authors list (link)
  5. ^ a b Archer, Cristina L.; Jacobson, Mark Z. (November 2007). "Supplying Baseload Power and Reducing Transmission Requirements by Interconnecting Wind Farms". Journal of Applied Meteorology and Climatology. 46 (11): 1701–1717. Bibcode:2007JApMC..46.1701A. CiteSeerX doi:10.1175/2007jamc1538.1. ISSN 1558-8424.
  6. ^ "Energy Dictionary - Baseload plant". EnergyVortex.com. Archived from the original on 2009-02-15. Retrieved 2008-08-03.
  7. ^ a b July 10; Alum, 2017 Kevin Steinberger-Alum Miles Farmer-. "Debunking Three Myths About "Baseload"". NRDC. Retrieved 2022-01-29.{{cite web}}: CS1 maint: numeric names: authors list (link)
  8. ^ "The Baseload Fallacy". Energy Global. 2023-08-02. Retrieved 2024-04-07.
  9. ^ a b Karel Beckman (11 September 2015). "Steve Holliday CEO National Grid: baseload is outdated". EnergyPost.eu. Archived from the original on 10 September 2016. Retrieved 6 October 2016.
  10. ^ Maurer, Luiz T.A., Luiz A. Barroso (2011). Electricity Auctions: An Overview of Efficient Practices (PDF). World Bank Publications. ISBN 978-0-8213-8822-8.{{cite book}}: CS1 maint: multiple names: authors list (link)
  11. ^ Nelder, Chris. "Why baseload power is doomed". ZDNet. Retrieved 2018-12-02.
  12. ^ "Scaling Geothermal for Reliable Baseload Power". renewableenergyworld.com. 2007-10-05. Archived from the original on 2018-07-01. Retrieved 2008-08-03.
  13. ^ Bird, Lori; Lew, Debra; Milligan, Michael; Carlini, E. Maria; Estanqueiro, Ana; Flynn, Damian; Gomez-Lazaro, Emilio; Holttinen, Hannele; Menemenlis, Nickie (November 2016). "Wind and solar energy curtailment: A review of international experience". Renewable and Sustainable Energy Reviews. 65: 577–586. doi:10.1016/j.rser.2016.06.082. ISSN 1364-0321.
  14. ^ GIMON, ERIC, ROBBIE ORVIS AND SONIA AGGARWAL (2015-03-23). "Renewables Curtailment: What We Can Learn From Grid Operations in California and the Midwest". Green Tech Media. Retrieved 2018-05-16.{{cite web}}: CS1 maint: multiple names: authors list (link)
  15. ^ Johnston, David Cay (2014-05-29). "OPINION: How electricity auctions are rigged to favor industry". Al Jazeera. Retrieved 2018-05-16.
  16. ^ "What is Generation Capacity?". Energy.gov. Retrieved 2022-06-18.
  17. ^ Ronald J. Daniels (1996). Ontario Hydro at the Millennium: Has Monopoly's Moment Passed?. Montreal and Kingston: McGill-Queen's University Press. ISBN 9780773514300. Retrieved 2008-08-03.
  18. ^ "Accelerating Just Transitions for the Coal Sector – Analysis". IEA. 2024-03-19. Retrieved 2024-04-06.
  19. ^ Nuclear Development, June 2011, page 10 from http://www.oecd-nea.org/
  20. ^ "Nuclear Development". www.oecd-nea.org. Nuclear Energy Agency. Retrieved 2018-12-02.
  21. ^ "A user's guide to natural gas power plants". Utility Dive. Retrieved 2022-06-18.
  22. ^ Stanley Reed (7 January 2019). "For Wales, Nuclear Plant Would Mean New Jobs. For the U.K., It May Mean More". New York Times.