2003-01-29
British thermal unit (Btu)
a unit of heat energy defined as the amount of heat required to raise the
temperature of one pound of water by one degree Fahrenheit. In America the
British thermal unit is sometimes called the heat unit. In
defining the Btu, it is necessary to specify the temperature of the water; thus
there have been several definitions over the years. However, one Btu is equal to
about 251.996 (small) calories, or
0.251 996 of the (kilo-)calories counted by dieters. Using the current
definition of the calorie (the IT calorie), one Btu equals
approximately 778.169 foot pounds, 1.055 056
kilojoules or 0.293 071 watt hour. The
symbol BThU has also been used, especially in Britain.
For all practical purpose a BTU is the same as a kilojoule. The therm
is not equal to 1000 BTUs. See below:
therm (thm)
a commercial unit of heat energy. The therm is equal to 100 000 Btu. Because there
have been several definitions of the Btu, there are two official definitions of
the therm. In the U.S., the legal definition (made in 1968) is that the therm
equals 105.4804 megajoules. The
European Union's definition, made in 1979 using the more current IT Btu, is
105.5060 megajoules. Either way the therm is equal to about 25 200 (large) calories or
about 29.3 kilowatt
hours of electrical energy. One therm can also be provided by about 96.7
cubic feet of natural gas. The therm has sometimes been confused with the
thermie (see below). The names of both units come from the Greek word for heat,
therme.
thermie (th)
a metric unit of heat energy, part of the meter-tonne-second system
sometimes used by European engineers. The thermie is equal to the amount of
energy required to raise the temperature of 1 tonne of water by 1�C. The thermie
is equivalent to 1000 (large) calories ,
4.1868 megajoules or
3968.3 Btu.
I hope all of this is helpful. If you ever need to clarify a unit, go
tot his site:
It should help clear up any confusion or questions you may have.
John
----- Original Message -----
Sent: Tuesday, 2003-01-28 23:06
Subject: [USMA:24662] Re: POWER Not SI
> John Nichols
<[EMAIL PROTECTED]> writes:
>
> My TXU gas bill has MCF as the units says they are thousands of
cubic
> > feet. Anne says I ask this question every time I
see the gas bill (she
> > hides them from me I beleive for that
reason) Is the M Roman thousand do
> > you think? Is that common
in the US gas industry?
>
> I strongly doubt it, but it certainly
varies from place to place.
>
> Where I live, PG&E (the gas
supplier for most of the northern 2/3 of
> California) prices its gas by
the "therm". A phone call revealed that a
> "therm" is defined as
1000 BTUs. This unit (actually determined for
> billing purposes by
measuring the volume used and the outdoor temperature,
> and applying a
complicated formula written by the state Public Utilities
> Commission) is
supposed to be fairer than pricing by volume because it
> allows for the
fact that the gas expands with temperature: one "therm" in
> the
summer occupies a greater volume but contains the same amount of gas.
>
> Does anyone here even recall how to convert the BTU to SI?
>
>
