MBH-thousands of Btus per hour-is also common. 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". The SI unit of power for heating and cooling systems is the watt. As a coarse approximation, 1,000 cubic feet (28 m 3) of natural gas yields ≈ 1,000,000 Btu ≈ 1 GJ.1 cubic foot (28 litres) 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.In natural gas pricing, the Canadian definition is that 1,000,000 Btu ≡ 1.054 615 GJ.
25,031 to 25,160 ft⋅pdl ( foot-poundal)Ī 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 one-pound (0.45 kg) weight 778 feet (237 m).The unit quad is commonly used to represent one quadrillion (10 15) BTUs. A decatherm is 10 therms or one MMBtu (million Btu). The unit ' therm' is used to represent 100,000 BTUs. Įnergy analysts accustomed to the metric "k" (' kilo-') for 1,000 are more likely to use MBtu to represent one million, especially in documents where M represents one million in other energy or cost units, such as MW, MWh and $. Even so, "MMbtu" is often used to indicate one million BTUs particularly in the oil and gas industry.
However, there is an ambiguity in that the metric system (SI) uses the prefix "M" to indicate ' Mega-', one million (1,000,000). The unit Mbtu is used in natural gas and other industries to indicate 1,000 BTUs. Energy Use Index (EUI) represents kBtu per square foot of conditioned floor area. Units of kBtu are used in building energy use tracking and heating system sizing.
British thermal unit calculator iso#
The BTU is then calculated from the calorie as is done for the thermochemical definitions of the BTU and the calorie, as in International standard ISO 31-4 Quantities and units-Part 4: Heat and British Standard BS 350:Part 1:1974 Conversion factors and tables. This definition ultimately became the statement that 1 IT calorie is exactly 4.1868 J. These conferences originally adopted the simplified definition that 860 "IT" calories corresponded to exactly 1 international watt-hour (not the same as a modern watt-hour). Īn early effort to define heat units directly in terms of energy units, and hence to remove the direct association with the properties of water, was taken by the International Steam Table Conferences. Uses the calorie value of water at its maximum density (4 ☌, 39.2 ☏). The thermochemical BTU is then defined using the conversions from grams to pounds and from Celsius to Fahrenheit. The International Standards Organization now defines the thermochemical calorie as exactly 4.184 J. The basis for its modern definition in terms of SI units is the similar, thermochemical calorie, which was originally defined as the heat required to raise the temperature of one gram of water from freezing to boiling divided by the temperature difference (100 ☌). Originally, the thermochemical BTU was defined as the heat required to raise the temperature of one pound of water from its freezing point to its boiling point, divided by the temperature difference, 180 ☏ (100 ☌). As seen in the table below, definitions of the BTU based on different water temperatures vary by up to 0.5%. This reflects the fact that the temperature change of a mass of water due to the addition of a specific amount of heat (calculated in energy units, usually joules) depends slightly upon the water's initial temperature. There are several different definitions of the BTU that differ slightly. Definitions Ī BTU was originally defined as the amount of heat required to raise the temperature of 1 avoirdupois pound of liquid water by 1 degree Fahrenheit at a constant pressure of one atmospheric unit. For example, in the United States the price of natural gas is quoted in dollars per the amount of natural gas that would give 1 million BTUs (1 "MMBtu") of heat energy if burned. While units of heat are often supplanted by energy units in scientific work, they are still used in some fields. The modern 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 see below). It is also part of the United States customary units. It is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. The British thermal unit ( BTU or Btu) is a measure of heat, which is measured in units of energy. For other uses, see BTU (disambiguation).
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