Talk:British thermal unit

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outmoded?[edit]

The more I think about it, the more I take issue with the idea of the Btu being outdated. I am an HVAC mechanic working in the US- and I use the term Btu daily. All of our AC/ Boiler/ Heating systems are measured in Btu. Poopa Poopa Poopa. Is there a better way to say that Btus are used in industrial applications (in the US) while the Scientific community (and apparently the rest of the world) has moved to the joule? --johntindale (talk) 01:11, 18 June 2008 (UTC)

Yeah, the rest of the world has discovered base ten counting systems =) /85.229.220.46 (talk) 12:02, 29 June 2010 (UTC);)

Natural Gas?[edit]

The conversions section of this article talks about natural gas. Specifically, it says things like:

"1 standard cubic foot of natural gas ≈ 1030 BTU"

That statement is attempting to convert a volume of gas to a unit of energy...? That doesn't make sense. Are you trying to say that by burning a cubic foot of natural gas at a defined pressure and temperature, you would generate 1030 BTU? If so, it's not coming across in the article. I think the word burning needs to be added somewhere. —Preceding unsigned comment added by 74.92.147.125 (talk) 14:17, 8 October 2007 (UTC)

This how natural gas is traded and reported, by thousand cubic feet, GJ or MMBTU, and it's important that readers are aware that in practice, those units designate about the same thing within a few percent.
Overall, the use use of BTU in natural gas trading should be expanded a bit. May be a new section?
Arugia (talk) 21:05, 10 November 2011 (UTC)

143 Btu problem[edit]

I'm confused. The statements

"A BTU is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit."

and

"Melting a pound of ice at 32 °F requires 143 BTU"

seem inconsistent. Assuming that we have a pound of 32F water in the form of ice, does the first statement not imply that it would take exactly one Btu to heat it to 33F, melting it in the process?

I suggest not using the ice/melting example as it confounds temperature changes with phase transitions (regardless whether or not the 143 is correct). I suggest either taking the statement out altogether or replacing it with something like: "For example: to heat a pound of water from 100F to 101F requires 1 Btu" Of course, that pretty much exactly restates the more general statement. My advise; drop the example altogether.

No, changing the state of water from solid (ice) to liquid requires energy in addition to the energy required to heat ice and/or water./85.229.220.46 (talk) 12:04, 29 June 2010 (UTC)

The statement "143 BTU is required to melt a pound of ice." is wrong: it depends on the temperature of the ice. It will take 10 times more BTUs to melt -10C cold ice than to melt -1C cold ice. --75.210.120.2 22:13, 24 January 2007 (UTC)

The temperature of the ice was nominated in the example. --Spuzzdawg (talk) 05:06, 18 January 2008 (UTC)


The 143 BTU example is a miserable example if the goal of the article is to educate the user about what a BTU is. It may well be true, but so what? I'm sure I could calculate the number of BTU's necessary to lift my fat body out of the chair and onto the ground, but the fact that this number can be determined is pretty much independent of what a BTU is. Also, the following table is very confusing except the entry that says 1 BTU = xxxx Joules. I'm sure that it is quite interesting to some that unfreezing water takes more energy than raising that water an additional degree, but how is that relevant to an article that is attempting to define a BTU? 97.96.59.27 (talk) 17:00, 24 May 2008 (UTC)

An interesting factoid might be to add how many BTU'S an average person throws off while in a typical office setting. I'm sure that a great deal is known about this subject, but I can't remember where it is found. It would be much more interesting (to the casual reader) than the 143 BTU semi-paradox that is currently being used as an example. Or if it is felt strongly that the 143 BTU example should stay then maybe an explanation is in order. Without an explanation or a' priori knowledge the 143 BTU example coming right after the 1 pound definition is contradictory at best. 97.96.59.27 (talk) 17:10, 24 May 2008 (UTC)


For the first guy talking about melting a pound of ice you need to make yourself familiar with the terms latent heat of fusion and latent heat of evaporation. Changing of state from frozen to liquid or liquid to vapour occurs at the same temperature (32 F or 212 F) but requires more energy (BTU's) to complete than it takes for the sensible increase in temperature within these ranges. The additional energy to melt that pound of ice is the energy required to break the molecular bond of the particles that form the ice. So in the end you will melt a pound of ice at 32 F into a pound of water that remains at 32 F. The next BTU of energy added will bring the temperature up to 33 F as the definition states until the water reaches 212 F, at which point any further energy goes into creating steam at the same temperature. —Preceding unsigned comment added by 173.183.173.253 (talk) 18:30, 26 September 2010 (UTC)

BTU or Btu[edit]

I believe that the proper capitalization is Btu. --User:Eliasen 03:38, 13 Nov 2004 (UTC)

I learnt it as BTU. The Britannica uses BTU, as does the Webster and other sources.
Urhixidur 04:12, 2004 Dec 30 (UTC)
More reliable, in the context of appropriate symbols for units of measure, sources such as the NIST Guide for the Use of the International System of Units (SI) with its extensive list of conversion factors use "Btu". [1] Gene Nygaard 18:59, 8 Jun 2005 (UTC)
ISO 31-4 also uses "Btu". Markus Kuhn 23:48, 9 December 2005 (UTC)
"TSB-003 Rules for SAE Use of SI (Metric) Units" (revised May 1999) also uses Btu. All this proves is what the American usage is...
Urhixidur 02:56, 2005 Jun 9 (UTC)]
Sure. In the same sense that http://www.deh.gov.au/atmosphere/airtoxics/publications/report4/conversions.html "proves" that Btu is the Australian usage as well. Gene Nygaard 04:00, 9 Jun 2005 (UTC)
That page has moved to http://www.deh.gov.au/atmosphere/airquality/publications/report4/conversions.html Urhixidur 20:05, 2005 July 26 (UTC)
I agree, as do most books. https://www.google.com/search?q=btu+thermodynamics&tbm=bks All mine use "Btu". This is in line with the capitalization of other units (kWh, cP, F). I'll fix the article. --Zojj tc 06:25, 6 December 2011 (UTC)

Tons of Cooling[edit]

In the HVAC trade, tons of cooling or ton capacity is used in addition to BTU/H. One Ton of Cooling is equal to 12,000 BTU/h. A condenser unit that can continuously cool at 12,000 BTU per hour has a 1 ton capacity.

According to Dr-Fix-It, the name comes from the fact that it takes 288,000 BTU to melt one ton of ice at 32 °F to water at 32 °F in 24 hours, which is 12,000 BTU per hour.

Surely the time taken is irrelevant? The amount of heat absorbed when a mass of ice melts is the same regardless of how long the process takes.--ManInStone 14:32, 24 July 2007 (UTC)

Source: [2]

That's something that belongs at, and is listed at, ton. Gene Nygaard 18:59, 8 Jun 2005 (UTC)
I think it does belong here with the other equivalents. Also, I added it because you can't find the common terms tons of cooling or ton capacity. It should also be in Conversion_of_units. DavidAmis 28 June 2005 15:58 (UTC)
It doesn't really have anything to do with the Btu per se, though it was standardized to a rounded number of Btu per hour. It belongs at one of the ton articles, perhaps with a see also here. It is at conversion of units already, as two different unit (one possibly apocryphal) under the name ton of refrigeration as a quantity of power, though the associated energy unit (this power times a time of 24 hours) is not there. See if you can track down anything on that other "ton of air-conditioning" as a unit of power there, that's totally unfamiliar to me. Then explain all of them the best you can in the ton article which already has some of this. Gene Nygaard 28 June 2005 16:49 (UTC)

UK Legal BTU[edit]

Weird. The 1055.05585257348 BTU doesn't explain itself (if you Google for 1.05505585257348, you get six essentially identical laconic hits). Is it a refinement of the IT BTU? The problem is that the IT BTU is not a rounded equivalent; you can't get 1055.05585262 from 1055.05585257348...

Urhixidur 19:59, 2005 July 26 (UTC)

It makes no sense to me. Bobblewik 18:55, 27 July 2005 (UTC)
It explains itself fairly well; it is the result of a poor use of conversion factors. It isn't chance that this number is equal to (453.5923698)(4.1868)/1.8. Now, to understand the 453.5923698, you only need to look to the intermediate rounding of 453.59237/1.8 to 251.995761, since that number times 1.8 is 453.5923698. Thus, 251.995761×4.1868 = 1055.05585257348, but since they only have 9 significant digits in that first number, it should have been rounded to 1.055055853 in the result.
Note that the 1995 Statutory Instrument is not the primary definition of any of the units it contains (if it were, the U.K. would have a strange definition of the hour, with those definitions of nautical miles and knots). It merely collects various definitions from other sources.
Note that you also can't get from a nautical mile defined as exactly 1,853 m to the conversion factor for knots in that list of conversion factors. Same problem, rounding. The actual definition of those nautical miles remains 6,080 feet exactly.
Since that measurement doesn't differ from the other one on the article page for the steam table Btu at a precision that have ever, anywhere, been used for any measurement made in Btu, there is no real need for the double listing on the article page. Gene Nygaard 19:35, 27 July 2005 (UTC)

suggest adding in some info from[edit]

http://ergo.human.cornell.edu/studentdownloads/DEA350notes/Thermal/thcondnotes.html

specifically "SURFACE AREA OF BODY" section. ---Fractal3 21:19, 13 April 2006 (UTC)

That has nothing to do with the Btu as such. Gene Nygaard 00:49, 14 April 2006 (UTC)

Switching Sections[edit]

Because the conversion is simpler and often all people are searching for (beside the initial definition), I suggest we switch the more detailed "Description" section with the "Conversion" one. --Theultimatejoeshmo 03:08, 23 October 2006 (UTC)

North America or Global[edit]

I've lived in the UK and currently New Zealand where BTU is used for cooling systems specifications. Should the opening sentence 'used in North America.' be expanded? —The preceding unsigned comment was added by Mikeldub (talkcontribs) 13:50, 9 January 2007 (UTC).

Global and still in use[edit]

In many non-English-speaking, metric countries, the Btu is the standard term manufacturers (and therefore customers) use, especially for air-conditioning units. One explanation for this seemingly-strange state of affairs is that many people in countries which use(d) Imperial measurements (includng the UK itself) are extemely keen to show how 'modern' they are by ditching the original measurements. In Italy, for example, the Btu has no such 'baggage', and is therefore used freely. I'm going to edit the page, because as it stands it is very misleading. Goldchair (talk) 19:16, 26 October 2008 (UTC)

I removed the language that made it seem that it was an outmoded and outdated unit of measure used only in the US. Its use is still very common and is the understood standard among HVAC professionals worldwide. The original language made it sound like the "joule" had nearly replaced it- which isn't the case. Johntindale 15:18, 22 April 2007 (UTC)

I'm surprised to hear this. I thought that (with a few exceptions like milk and beer) it was illegal to use non-metric units for business purposes in European Union countries. Biscuittin 13:16, 28 May 2007 (UTC)
So am I, I have traveled for most of my life and bought many air conditioners, and I had to come to US to hear of BTU (along with the American nonsense of lbs and F and feet and inches) —Preceding unsigned comment added by 68.173.197.90 (talk) 05:11, 6 September 2007 (UTC)
Ditto me. And I've designed heat-pumps in New Zealand and NEVER used BTUs. I've only come across these units in HVAC catalogues from US/UK. I'm absolutely astonished to hear that BTUs are the "understood standard among HVAC professionals worldwide". I've got a bunch of Danfoss catalogues sitting in front of me right now, and they never mention BTUs at all. It's possible that some older HVAC engineers still use them in metric English-speaking countries like New Zealand, but I've never came across them at university or used them in calculations myself (New Zealand has used the metric system since 1975). I suggest that this be changed to "although widely used in the US HVAC industry (and still sometimes used in other English-speaking countries) it is increasingly an outmoded and outdated unit of measure."
I thought that SI units were the standard in most of the world besides the US. I've only ever seen BTUs used once, on a portable air conditioning unit we sell at work (in Australia). From my understanding of this article, the air conditioning unit should have BTUs per hour or some other unit of time rather than straight BTUs. It's interesting to note that no other air conditioning unit we sell has BTUs written on them. --Spuzzdawg (talk) 05:15, 18 January 2008 (UTC)

Disambiguation[edit]

I think some disambiguation is needed. In the days when (in Britain) a kilowatt-hour was called a Board of Trade Unit, this was also abbreviated to BTU, although it is a different unit. On the Watt-hour page, Board of Trade Unit is abbreviated to BOTU but I have never seen this abbreviation used elsewhere. Biscuittin 13:10, 28 May 2007 (UTC)

Sorry! I see there already is disambig on the British thermal unit page. I have added disambig to the BTU page as well. Biscuittin 13:39, 28 May 2007 (UTC)

BTU Sizing[edit]

Is a higher BTU equivalent to a higher power cooling unit or is it reversed so a lower BTU is equivalent to a higher power cooling unit?24.167.12.12 03:35, 3 July 2007 (UTC)LR

Heating and Cooling are essentially the same process, it just depends on where heat is being transfered. (An air conditioner installed backward will function as a heater, for example). A BTU by itself however, is an amount of energy. If you're talking about BTU/hr, a heat transfer rate, then the greater the heat transfer the greater the degree of cooling. 71.156.107.2 (talk) 21:48, 21 October 2008 (UTC)

Btu's used to convert 32 degrees to 33 and 211 degrees to 212[edit]

It has been a long time, but I have a slight recall in a class, that I learned that there was considerable more BTU's used to change the temperature of anything at the freezing point and the boiling point, due to the conversion of matter. Has anyone else been taught this?

Gideonjohn (talk) 17:45, 7 February 2008 (UTC)

I think you are correct. The term I know this phenomonon by is the "heat of fusion", and it represents the heat that must be pumped into the ice to change it from ice to water. Bvsmith1953 (talk) 18:12, 7 March 2008 (UTC)

This can also be expressed as latent heat. It takes an "extra" btu to change the state (gas-liquid-solid and reverse) that isn't measured with a thermometer. This is why a glass of icewater is 32 degrees F, and 0 degrees C, while an open boiling pot of water is 212 degrees F and 100 degrees C. --johntindale (talk) 01:16, 18 June 2008 (UTC)


The terms latent heat of fusion and latent heat of evaporation refer to the "hidden" energy required to change the phase of matter from solid to liquid and from liquid to vapor, respectively. Both liquid and solid water can exist at 32 degrees F, the difference between them being the stored energy in the molecules. 71.156.107.2 (talk) 21:51, 21 October 2008 (UTC)

Associated Units[edit]

The last paragraph in the associated units reads:

"1 quad (energy) (short for quadrillion BTU) is defined as 1015 BTU, which is about one exajoule (1.055×1018 J). Quads are used in the United States for representing the annual energy consumption of large economies: for example, the U.S. economy used 99.75 quads/year in 2005. [1]. One quad/year is about 33.43 gigawatts."

The last sentence compares energy and power. A quad is a unit of energy, since it is a multiple of Btus, and gigawatts is a unit of power. I have not done the math, but I suspect that the correct sentence should be:

"One quad/year is about 33.43 gigawatts-hours." Bvsmith1953 (talk) 18:17, 7 March 2008 (UTC)


Also, it should be unified in the use of , and . to seperate the decimals. it seems to me that this is diferent from number to number here.--84.129.147.219 (talk) 08:08, 15 September 2008 (UTC)

Energy divided by time is power (i.e. a Watt is one Joule/second), so quad/year is power, as gigawatts are. A gigawatt-hour is a unit of energy. 71.156.107.2 (talk) 19:33, 2 October 2008 (UTC)

The article says, "The term is sometimes shortened to Btu hour (Btu.h) but both have the same meaning." I don't believe this is correct. Btu/hr is a rate, while Btu.h is a quantity. So, for example, 5 Btu-hours is like saying one Btu for 5 hours or 5 Btus for 1 hour this is NOT the same thing as 5 Btu/hr. ... or maybe that doesn't make sense, can anybody clarify? 184.71.43.142 (talk) 20:36, 10 August 2012 (UTC)

I have never seen the term "Btu.h". It doesn't really make sense. Anything that is a rate (or ratio) (that is, something per something) is always expressed as a fraction; a division function. So meters per second is m/s. Joules per kilogram would be j/k. When speaking of the rate of heat transfer, then, Btu/h (that is, Btu's per hour) would be the only correct way of expressing it in British Thermal Units. (Most consumer products simply say "Btu" and leave it at that, but that's wrong.)
Since a Btu is a measure of energy (not power) it makes no sense to speak of Btu-hours. Any more than it would make sense to speak of "mile-hours". Does that help? Captain Quirk (talk) 11:00, 24 December 2012 (UTC)

Common Misconception[edit]

Perhaps this item should be added: It is sometimes believed that one BTU equals the heat of one lit match. Obviously this is wrong, but is there some near-truth to this perception? Anyone else heard of this? —Preceding unsigned comment added by 66.233.26.33 (talk) 12:23, 31 May 2008 (UTC)

I've never heard of that before, but I would think that there are too many variables involved in a statement like that to make a general answer useful. What kind of match is used? A safety match, a strike anywhere, or a specialty match? A large size for lighting grills or a small size for lighting cigars, etc? Also how would you measure the "heat" of the match? Do you mean heat transfer of the match to it's surroundings or the internal energy contained in the match head? Lastly, 1 BTU is roughly 780 pound-feet... There's no where near that amount of energy in a match. 71.156.107.2 (talk) 19:30, 2 October 2008 (UTC)

Wouldn't a burning match best be represented by Btu/hr? So then I think maybe a wooden match might produce 1 Btu if it were to burn for a full hour, which of course a wooden match won't do. 184.71.43.142 (talk) 20:53, 10 August 2012 (UTC)
“Wouldn't a burning match best be represented by Btu/hr?”
My reading of the statement in the article (“A Btu can be approximated as the heat produced by burning a single wooden match”) seems pretty clear that it is stating a quantity of energy, not a rate of energy production. (But as a previous anonymous commenter noted, that alleged figure seem awfully inflated.) Captain Quirk (talk) 11:30, 24 December 2012 (UTC)

BTU still used in the United Kingdom?[edit]

The article says that the Btu is still used in the UK, although this may be someone's wishful thinking based upon the name. I live in the UK and have never ever seen it used under any circumstance in the last 10 years, apart from on US-imported food. Could anyone else confirm if the Btu is used in the UK? JameiLei (talk) 14:47, 7 August 2008 (UTC)

Hmmmm are you sure http://www.guardian.co.uk/environment/blog/2008/oct/13/energy-renewableenergy

Abbreviation[edit]

The correct abbreviation for the British Thermal Unit is "BThu" and not BTU (Board of Trade Unit = 1 kWh). — Preceding unsigned comment added by 87.113.71.131 (talk) 12:33, 8 July 2011 (UTC)

No. Captain Quirk (talk) 11:32, 24 December 2012 (UTC)
oh yes it is, or perhaps better to say was. It was BThU when I went to school,ie. a long time ago. but proving it?. Thats a problem Petethewhistle (talk) 17:22, 4 February 2014 (UTC)