Watt

== Multiples ==
{{For|additional examples of magnitude for multiples and submultiples of the watt|Orders of magnitude (power)}}
{{SI multiples
|unit=watt
|symbol=W
|note=Common multiples are in '''bold''' face
|p=|n=|mc=|m=|k=|M=|G=|T=|P=|f=
}}

;<span id="Attowatt">Attowatt</span>: The sound intensity in water corresponding to the international standard reference [[sound pressure]] of 1&nbsp;[[micropascal|μPa]] is approximately 0.65&nbsp;aW/m<sup>2</sup>.<ref>Ainslie, M. A. (2015). A century of sonar: Planetary oceanography, underwater noise monitoring, and the terminology of underwater sound. Acoustics Today.</ref>
;<span id="Femtowatt">Femtowatt</span>: Powers measured in femtowatts are typically found in references to [[radio]] and [[radar]] receivers. For example, meaningful [[FM tuner]] performance figures for sensitivity, quieting and [[Signal-to-noise ratio|signal-to-noise]] require that the [[Radio frequency|RF]] energy applied to the antenna input be specified. These input levels are often stated in dBf ([[decibel]]s referenced to 1 femtowatt). This is 0.2739 microvolts across a 75-ohm load or 0.5477 microvolt across a 300-ohm load; the specification takes into account the RF [[input impedance]] of the tuner.
;<span id="Picowatt">Picowatt</span>: Powers measured in picowatts are typically used in reference to radio and radar receivers, [[acoustics]] and in the science of [[radio astronomy]]. One picowatt is the international standard reference value of [[sound power]] when this quantity is expressed in decibels.<ref>Morfey, C.L. (2001). Dictionary of Acoustics.</ref>
;<span id="Nanowatt">Nanowatt</span>: Powers measured in nanowatts are also typically used in reference to radio and radar receivers.
;<span id="Microwatt">Microwatt</span>: Powers measured in microwatts are typically stated in [[medical instrument]]ation systems such as the [[Electroencephalography|electroencephalograph]] (EEG) and the [[Electrocardiography|electrocardiograph]] (ECG), in a wide variety of scientific and engineering instruments and also in reference to radio and radar receivers. Compact [[solar cells]] for devices such as [[Solar-powered calculator|calculators]] and [[Solar-powered watch|watches]] are typically measured in microwatts.<ref>{{Citation | newspaper = The New York Times | url = https://www.nytimes.com/2010/07/18/business/18novel.html | title = Bye-Bye Batteries: Radio Waves as a Low-Power Source | date = Jul 18, 2010 | url-status = live | archive-url = https://web.archive.org/web/20170321231716/http://www.nytimes.com/2010/07/18/business/18novel.html | archive-date = 2017-03-21 }}.</ref>
;<span id="Milliwatt">Milliwatt</span>: A typical [[laser pointer]] outputs about five milliwatts of light power, whereas a typical [[hearing aid]] uses less than one milliwatt.<ref>{{cite web | url = http://www.datasheetarchive.com/datasheet-pdf/019/DSA00333218.html | title = Low-Power Real-Time Programmable DSP Development Platform for Digital Hearing Aids | first1 = Trudy | last1 = Stetzler | first2 = Neeraj | last2 = Magotra | first3 = Pedro | last3 = Gelabert | first4 = Preethi | last4 = Kasthuri | first5 = Sridevi | last5 = Bangalore | publisher = Datasheet Archive | access-date = 8 February 2010 | url-status = live | archive-url = https://web.archive.org/web/20110303094710/http://www.datasheetarchive.com/datasheet-pdf/019/DSA00333218.html | archive-date = 3 March 2011 }}</ref> [[Audio signal]]s and other electronic signal levels are often measured in [[dBm]], referenced to one milliwatt.
;<span id="Kilowatt">Kilowatt</span>
{{Redirect2 |Kilowatt|Kilowatts|the musician James Watts|KiloWatts (musician)}}
{{redirect|kW}}
:The kilowatt is typically used to express the output power of [[engine]]s and the power of [[electric motor]]s, tools, machines, and heaters. It is also a common unit used to express the [[Electromagnetic radiation|electromagnetic]] power output of broadcast radio and television [[transmitter]]s. {{paragraph}} One kilowatt is approximately equal to 1.34 [[horsepower]]. A small electric heater with one [[heating element]] can use 1 kilowatt. The average [[Electric energy consumption|electric power consumption]] of a household in the United States is about 1 kilowatt.{{efn-lr|Average household electric power consumption is 1.19&nbsp;kW in the US, 0.53&nbsp;kW in the UK.  In India it is 0.13&nbsp;kW (urban) and 0.03&nbsp;kW (rural) – computed from GJ figures quoted by Nakagami, Murakoshi and Iwafune.<ref>{{cite conference
 |conference    = ACEEE Summer Study on Energy Efficiency in Buildings
 |year          = 2008
 |conference-url = http://aceee.org/conferences/2008/ssb
 |publisher     = American Council for an Energy-Efficient Economy
 |location      = [[Pacific Grove, California]]
 |title         = International Comparison of Household Energy Consumption and Its Indicator
 |url           = http://www.aceee.org/files/proceedings/2008/data/papers/8_24.pdf
 |first1        = Hidetoshi
 |last1         = Nakagami
 |first2        = Chiharu
 |last2         = Murakoshi
 |first3        = Yumiko
 |last3         = Iwafune
 |at            = Figure 3. Energy Consumption per Household by Fuel Type. 8:214–8:224
 |access-date    = 14 February 2013
 |url-status       = live
 |archive-url    = https://web.archive.org/web/20150109012214/http://www.aceee.org/files/proceedings/2008/data/papers/8_24.pdf
 |archive-date   = 9 January 2015
}}</ref>
}} {{paragraph}} A surface area of 1 square meter on Earth receives typically about one kilowatt of sunlight from the Sun (the [[solar irradiance]]) (on a clear day at midday, close to the equator).<ref>Elena Papadopoulou, ''Photovoltaic Industrial Systems: An Environmental Approach'', Springer 2011 {{ISBN|3642163017}},  p.153</ref>
;<span id="Megawatt">Megawatt</span>: Many events or machines produce or sustain the conversion of energy on this scale, including large electric motors; large warships such as aircraft carriers, cruisers, and submarines; large [[server farm]]s or [[Data center#Energy use|data centers]]; and some scientific research equipment, such as [[supercollider]]s, and the output pulses of very large lasers. A large residential or commercial building may use several megawatts in electric power and heat. On railways, modern high-powered [[electric locomotive]]s typically have a peak power output of {{val|5|or|6|u=MW}}, while some produce much more. The [[British Rail Class 373|Eurostar e300]], for example, uses more than {{val|12|u=MW}}, while heavy [[Diesel electric locomotive|diesel-electric locomotives]] typically produce and use {{val|3|and|5|u=MW}}. U.S. [[nuclear power plant]]s have net summer capacities between about {{val|500|and|1300|u=MW}}.<ref>{{cite report | chapter-url = https://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1350/v19/sr1350v19.pdf | publisher = [[Nuclear Regulatory Commission|United States Nuclear Regulatory Commission]] | language = en-us | date = 2007-08-01 | title = 2007–2008 Information Digest | chapter = Appendix A {{!}} U.S. Commercial Nuclear Power Reactors | pages = 84{{hyphen}}101 | issue = NUREG-1350 | volume = 19 | access-date = 2021-12-27 | url-status = dead | archive-url = https://web.archive.org/web/20080216073347/http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1350/v19/sr1350v19.pdf | archive-date = 2008-02-16 | df = dmy-all }}</ref>{{rp|pp=84{{hyphen}}101}} {{paragraph}} The earliest citing of the megawatt in the ''[[Oxford English Dictionary]]'' (''OED'') is a reference in the 1900 [[Webster's Dictionary|''Webster's International Dictionary of the English Language'']]. The ''OED'' also states that ''megawatt'' appeared in a 28 November 1947 article in the journal ''[[Science (journal)|Science]]'' (506:2).
[[File:Office of Nuclear Energy video explaining gigawatts.ogg|thumb|A [[United States Department of Energy]] video explaining gigawatts]]
;<span id="Gigawatt">Gigawatt</span>: A gigawatt is typical average power for an industrial city of one million habitants and also the output of a large power station. The GW unit is thus used for large power plants and [[Electrical grid|power grids]]. For example, by the end of 2010, power shortages in China's Shanxi province were expected to increase to 5–6&nbsp;GW<ref>{{cite web | place = Peking | first1 = Jim | last1 = Bai | first2 = Aizhu | last2 = Chen | editor-first = Chris | editor-last = Lewis | url = http://in.reuters.com/article/idINTOE6AA0AD20101111 | title = China's Shanxi to face 5–6 GW power shortage by yr-end – paper | date = 11 November 2010 | publisher = Reuters}}</ref> and the installation capacity of wind power in Germany was 25.8 GW.<ref>{{cite news | url=http://www.economist.com/node/16846774 | title=Not on my beach, please | newspaper=The Economist | date=19 August 2010 | url-status=live | archive-url=https://web.archive.org/web/20100824080835/http://www.economist.com/node/16846774 | archive-date=24 August 2010 }}</ref> The largest unit (out of four) of the Belgian [[Doel Nuclear Power Station]] has a peak output of 1.04&nbsp;GW.<ref>{{cite web | language = fr | series = Who are we: Nuclear | url= http://www.electrabel.com/whoarewe/nuclear/keyfigures_doel.aspx | title = Chiffres clés |trans-title=Key numbers | year = 2011 | work = Electrabel |archive-url=https://web.archive.org/web/20110710180653/http://www.electrabel.com/whoarewe/nuclear/keyfigures_doel.aspx |archive-date=2011-07-10}}</ref> [[HVDC converter]]s have been built with power ratings of up to 2&nbsp;GW.<ref>{{Citation | last1 = Davidson | first1 = CC | last2 = Preedy | first2 = RM | last3 = Cao | first3 = J | last4 = Zhou | first4 = C | last5 = Fu | first5 = J | contribution = Ultra-High-Power Thyristor Valves for HVDC in Developing Countries | publisher = [[Institution of Engineering and Technology|IET]] | title = 9th International Conference on AC/DC Power Transmission | place = London | date = October 2010}}.</ref>
;<span id="Terawatt">Terawatt</span>: The [[primary energy]] used by humans worldwide was about 160,000&nbsp;terawatt-hours in 2019, corresponding to an average continuous power consumption of 18&nbsp;TW that year.<ref>{{Cite journal |url=https://ourworldindata.org/grapher/global-primary-energy?country=~OWID_WRL |title=Global Direct Primary Energy Consumption |author1=Hannah Ritchie |author1-link=Hannah Ritchie |author2=Max Roser |author2-link=Max Roser |journal=Our World in Data |publisher=Published online at OurWorldInData.org. |year=2020 |access-date=2020-02-09}}</ref> The most powerful lasers from the mid-1960s to the mid-1990s produced power in terawatts, but only for [[nanosecond]] intervals. The average lightning strike peaks at 1&nbsp;TW, but these strikes only last for 30 [[microsecond]]s.
;<span id="Petawatt">Petawatt</span>: A petawatt can be produced by the current generation of lasers for time scales on the order of picoseconds. One such laser is [[Lawrence Livermore National Laboratory|Lawrence Livermore]]'s [[Nova (laser)|Nova laser]], which achieved a power output of 1.25&nbsp;PW by a process called [[chirped pulse amplification]]. The duration of the pulse was roughly 0.5&nbsp;[[picosecond|ps]], giving a total energy of 600&nbsp;J.<ref>{{cite web |url = https://www.llnl.gov/str/Petawatt.html |title = Crossing the Petawatt threshold |publisher = Lawrence Livermore National Laboratory |location = [[Livermore, California|Livermore]], [[California|CA]] |access-date = 19 June 2012 |url-status = live |archive-url = https://web.archive.org/web/20120915212555/https://www.llnl.gov/str/Petawatt.html |archive-date = 15 September 2012 }}</ref> Another example is the Laser for Fast Ignition Experiments (LFEX) at the Institute of Laser Engineering (ILE), [[Osaka University]], which achieved a power output of 2&nbsp;PW for a duration of approximately 1&nbsp;[[picosecond|ps]].<ref>{{citation | title = World's most powerful laser: 2 000 trillion watts. What's it? | date = 12 August 2015 | publisher = IFL Science | url = http://www.iflscience.com/technology/world-s-most-powerful-laser-2000-trillion-watts-what-s-it | url-status = live | archive-url = https://web.archive.org/web/20150822093000/http://www.iflscience.com/technology/world-s-most-powerful-laser-2000-trillion-watts-what-s-it | archive-date = 2015-08-22 }}.</ref><ref>{{Citation | title = Eureka alert | type = publicity release | date = Aug 2015 | url = http://www.eurekalert.org/pub_releases/2015-08/ou-wpl080615.php | url-status = live | archive-url = https://web.archive.org/web/20150808055653/http://www.eurekalert.org/pub_releases/2015-08/ou-wpl080615.php | archive-date = 2015-08-08 }}.</ref> {{paragraph}} Based on the average total solar irradiance of 1.361&nbsp;kW/m<sup>2</sup>,<ref name=TSI>{{cite web | title = Construction of a Composite Total Solar Irradiance (TSI) Time Series from 1978 to present | publisher = PMODWRC | url = http://www.pmodwrc.ch/pmod.php?topic=tsi/composite/SolarConstant | place = [[Switzerland|CH]] | access-date = 2005-10-05 | url-status = live | archive-url = https://web.archive.org/web/20110830221302/http://www.pmodwrc.ch/pmod.php?topic=tsi/composite/SolarConstant | archive-date = 2011-08-30 }}</ref> the total power of sunlight striking Earth's atmosphere is estimated at 174&nbsp;PW. The planet's average rate of global warming, measured as [[Earth%27s_energy_budget#Earth's energy imbalance (EEI)|Earth's energy imbalance]], reached about 0.5&nbsp;PW (0.3% of incident solar power) by 2019.<ref>{{cite journal |last1=Loeb |first1=Norman G. |last2=Johnson |first2=Gregory C. |last3=Thorsen |first3=Tyler J. |last4=Lyman |first4=John M. |last5=Rose |first5=Fred G. |last6=Kato |first6=Seiji |display-authors=4 |title=Satellite and Ocean Data Reveal Marked Increase in Earth's Heating Rate |journal=Geophysical Research Letters |date=15 June 2021 |volume=48 |issue=13 |doi=10.1029/2021GL093047 |bibcode=2021GeoRL..4893047L |doi-access=free }}</ref>
;<span id="Yottawatt">Yottawatt</span>: The power output of the Sun is 382.8&nbsp;YW, about 2 billion times the power estimated to reach Earth's atmosphere.<ref name="Sun Fact Sheet">{{cite web |last1=Williams |first1=David R. |title=Sun Fact Sheet |url=https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html |website=nasa.gov |publisher=NASA |access-date=26 February 2022}}</ref>