British thermal unit: Difference between revisions
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imported>NebY Undid revision 1352783475 by ~2026-27444-79 (talk) see body of article and source |
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{{Use dmy dates|date=July 2020}} | {{Use dmy dates|date=July 2020}} | ||
{{Infobox unit | {{Infobox unit | ||
| name | | name = British thermal unit | ||
| image | | image = US energy consumption.svg | ||
| caption | | caption = Graph of total energy consumption in the US (divided into energy sources) in quadrillion Btu | ||
| standard | | standard = [[Imperial units|Imperial]]/[[US customary system|US]] units | ||
| quantity | | quantity = [[Energy]] (heat) | ||
| symbol | | symbol = Btu | ||
| extralabel | | extralabel = | ||
| extradata | | extradata = | ||
| units1 = SI units | | units1 = SI units | ||
| inunits1 | | inunits1 = ≈ {{Val|1055|ul=J}} | ||
}} | }} | ||
The '''British thermal unit''' ('''Btu''') is a measure of [[heat]], which is a form of [[energy]]. It was originally defined as the amount of heat required to raise the temperature of one [[pound (mass)|pound]] of water by one degree [[Fahrenheit]]. It is also part of the [[United States customary units]].<ref>In a short note, Woledge notes that the actual technical term "British thermal unit" apparently originated in the United States, and was subsequently adopted in Great Britain. See {{cite journal |last1=Woledge |first1=G. |date=30 May 1942 |title=History of the British Thermal Unit |journal=Nature |volume=149 |page=613 |bibcode=1942Natur.149..613W |doi=10.1038/149613c0 |s2cid=4104904 |doi-access=free |number=149}}</ref> The [[SI]] unit for energy is the [[joule (J)]]; one Btu equals about 1,055 J (varying within the range of 1,054–1,060 J depending on the specific definition of Btu; see below). | The '''British thermal unit''' ('''Btu''') is a measure of [[heat]], which is a form of [[energy]]. It was originally defined as the amount of heat required to raise the temperature of one [[pound (mass)|pound]] of water by one degree [[Fahrenheit]]. It is also part of the [[United States customary units]].<ref>In a short note, Woledge notes that the actual technical term "British thermal unit" apparently originated in the United States, and was subsequently adopted in Great Britain. See {{cite journal |last1=Woledge |first1=G. |date=30 May 1942 |title=History of the British Thermal Unit |journal=Nature |volume=149 |page=613 |bibcode=1942Natur.149..613W |doi=10.1038/149613c0 |s2cid=4104904 |doi-access=free |number=149}}</ref> The [[SI]] unit for energy is the [[joule (J)]]; one Btu equals about 1,055 J (varying within the range of 1,054–1,060 J depending on the specific definition of Btu; see below). | ||
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A Btu can be approximated as the heat produced by burning a single wooden kitchen match or as the amount of energy it takes to lift a {{convert|1|lb|spell=in|adj=on}} weight {{Convert|778|ft|m|0}}.<ref name="RistinenKraushaar2006">{{cite book|last1=Ristinen|first1=Robert A. |last2=Kraushaar|first2=Jack J. |title=Energy and the Environment|url=https://archive.org/details/energyenvironmen00rist|url-access=registration|year=2006|publisher=John Wiley & Sons|isbn=978-0-471-73989-0|pages=[https://archive.org/details/energyenvironmen00rist/page/13 13]–14}}</ref> | A Btu can be approximated as the heat produced by burning a single wooden kitchen match or as the amount of energy it takes to lift a {{convert|1|lb|spell=in|adj=on}} weight {{Convert|778|ft|m|0}}.<ref name="RistinenKraushaar2006">{{cite book|last1=Ristinen|first1=Robert A. |last2=Kraushaar|first2=Jack J. |title=Energy and the Environment|url=https://archive.org/details/energyenvironmen00rist|url-access=registration|year=2006|publisher=John Wiley & Sons|isbn=978-0-471-73989-0|pages=[https://archive.org/details/energyenvironmen00rist/page/13 13]–14}}</ref> | ||
=== Btu conversion factors === | |||
For purposes of {{clarify span|text=site energy|date=September 2025}}, the following conversion factors apply:<ref>{{cite web | url=https://photius.com/energy/glossaryb.html#Btu_conv | title=Btu conversion factors | access-date=15 September 2025 | publisher=Energy Dictionary | archive-url=https://web.archive.org/web/20250830073644/https://photius.com/energy/glossaryb.html#Btu | archive-date=30 August 2025 }}</ref> | |||
* Electricity: 3,412 Btu/kilowatthour | |||
* Natural gas: 1,031 Btu/cubic foot | |||
* [[Fuel oil]] No. 1: 135,000 Btu/gallon | |||
* [[Kerosene]]: 135,000 Btu/gallon | |||
* Fuel oil No. 2: 138,690 Btu/gallon | |||
* LPG ([[propane]]): 91,330 Btu/gallon | |||
* Wood: 20 million Btu/cord | |||
=== For natural gas === | === For natural gas === | ||
{{main|Natural gas prices}} | {{main|Natural gas prices}} | ||
* In [[natural gas]] pricing, the Canadian definition is that {{val|1000000|u=Btu|fmt=commas}} ≡ {{val|1.054615|u=GJ}}.<ref name=Alberta>{{cite web | url=http://www.energy.gov.ab.ca/about_us/1132.asp | title=Energy Measurements | access-date=7 January 2017 | publisher=Government of Alberta Province | url-status=dead | archive-url=https://web.archive.org/web/20170120191331/http://www.energy.gov.ab.ca/About_Us/1132.asp | archive-date=20 January 2017 | df=dmy-all }}</ref> | * In [[natural gas]] pricing, the Canadian definition is that {{val|1000000|u=Btu|fmt=commas}} ≡ {{val|1.054615|u=GJ}}.<ref name=Alberta>{{cite web | url=http://www.energy.gov.ab.ca/about_us/1132.asp | title=Energy Measurements | access-date=7 January 2017 | publisher=Government of Alberta Province | url-status=dead | archive-url=https://web.archive.org/web/20170120191331/http://www.energy.gov.ab.ca/About_Us/1132.asp | archive-date=20 January 2017 | df=dmy-all }}</ref> | ||
* The energy content (high or low heating value) of a volume of natural gas varies with the composition of the natural gas, which means there is no universal conversion factor for energy to volume. {{convert|1|ft3|L|abbr=off}} of average natural gas yields ≈ 1,030 Btu (between 1,010 Btu and 1,070 Btu, depending on quality, when burned) | * The energy content (high or low heating value) of a volume of natural gas varies with the composition of the natural gas, which means there is no universal conversion factor for energy to volume. {{convert|1|ft3|L|abbr=off}} of average natural gas yields ≈ 1,030 Btu (between 1,010 Btu and 1,070 Btu, depending on quality, when burned) | ||
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===Btu/h=== | ===Btu/h=== | ||
The SI unit of [[Power (physics)|power]] for heating and cooling systems is the [[watt]]. Btu ''per hour'' (Btu/h) is sometimes used in North America and the United | The SI unit of [[Power (physics)|power]] for heating and cooling systems is the [[watt]]. Btu ''per hour'' (Btu/h) is sometimes used in North America and the United Kingdom—the latter for air conditioning mainly, though "Btu/h" is sometimes abbreviated to just "Btu".<ref>{{cite book|title=Masonry Heaters: Designing, Building, and Living with a Piece of the Sun|author=Ken Matesz|page=148|publisher=Chelsea Green Publishing|year=2010}}</ref> ''MBH''—thousands of Btu per hour—is also common.<ref>{{Cite book |last=Arimes |first=Tom |oclc=32314774 |title=HVAC and chemical resistance handbook for the engineer and architect : a compilation |publisher=BCT |year=1994 |isbn=0-9640967-0-6 |location=Lexington, Ky. |page=11-12 }}</ref> | ||
* 1 W is approximately {{convert|1|W|Btu/h|disp=out|sigfig=7}}<ref>{{cite web|url=http://app.knovel.com/web/toc.v/cid:kpASHRAE22/viewerType:toc/root_slug:ashrae-handbook-fundamentals/url_slug:ashrae-handbook-fundamentals/|title=2009 ASHRAE Handbook – Fundamentals (I-P Edition)|url-status=live|archive-url=https://web.archive.org/web/20151017172515/http://app.knovel.com/web/toc.v/cid:kpASHRAE22/viewerType:toc/root_slug:ashrae-handbook-fundamentals/url_slug:ashrae-handbook-fundamentals/|archive-date=17 October 2015|access-date=21 September 2015|publisher=[[ASHRAE|American Society of Heating, Refrigerating and Air-Conditioning Engineers]], Inc}}</ref> | * 1 W is approximately {{convert|1|W|Btu/h|disp=out|sigfig=7}}<ref>{{cite web|url=http://app.knovel.com/web/toc.v/cid:kpASHRAE22/viewerType:toc/root_slug:ashrae-handbook-fundamentals/url_slug:ashrae-handbook-fundamentals/|title=2009 ASHRAE Handbook – Fundamentals (I-P Edition)|url-status=live|archive-url=https://web.archive.org/web/20151017172515/http://app.knovel.com/web/toc.v/cid:kpASHRAE22/viewerType:toc/root_slug:ashrae-handbook-fundamentals/url_slug:ashrae-handbook-fundamentals/|archive-date=17 October 2015|access-date=21 September 2015|publisher=[[ASHRAE|American Society of Heating, Refrigerating and Air-Conditioning Engineers]], Inc}}</ref> | ||