British Thermal Units’, the unit in which radiator efficiency is measured,Factors such as room dimensions, window size and wall material are used to calculate the required outputs of radiators, in order to adequately heat a room. An approximation of the amount of energy required. A British Thermal Unit (BTU) is the amount of heat energy needed to raise the temperature of one pound of water by one degree F. This is the standard measurement used to state the amount of energy that a fuel has as well as the amount of output of any heat generating device.
BTU, or British thermal unit, is the industry-standard used to measure the heating efficiency of furnaces. In addition to BTU ratings, furnace manufacturers might include a Manual J Load rating and a percentage of energy efficiency. BTUs Explained. BTU is a unit of measurement that measures the amount of energy required to raise the temperature of one pound of water by one degree Fahrenheit. Furnaces are measured in how many BTUs they use per hour to achieve this temperature increase. A British Thermal Unit (BTU) is an approximation of the amount of energy required to heat 1lb (one pound) of water from 39°F to 40°F (degrees Fahrenheit), and is roughly equal to 1.055 KJoules. Simplified, 1 BTU is roughly the amount of heat produced by burning a single wooden match. BTUs are ‘British Thermal Units’, the unit in which radiator efficiency is measured. Factors such as room dimensions, window size and wall material are used to calculate the required outputs of radiators, in order to adequately heat a room. A BTU is a measurement of thermal energy where one BTU is equal to the amount of energy needed to raise the temperature of 1 pound of water by 1° Fahrenheit. Even small space heaters can produce thousands of BTUs. A central air conditioner, which uses hundreds of thousands of BTUs. Re: dougsherman's post. 1 BTU is roughly 1055 joules of heat, or energy. You are mistaking joules with joules/second. Regardless of how long it takes to expose the water to 1 BTU of heat, 1 BTU of heat will raise the temperature of 1 pound of water 1 degree The British thermal unit (BTU or Btu) is a traditional unit of work equal to about 1055 joules. It is the amount of work needed to raise the temperature of one pound of water by one degree Fahrenheit (Physical analogue: one four-inch wooden kitchen match consumed completely generates approximately 1 BTU). A BTU is 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 atmosphere. calorie, several definitions of the BTU exist, because the temperature response of water to heat energy is non-linear. Radiator BTU calculator. The heat output or 'BTU' (British Thermal Unit) calculator is a great way to work out how much radiator power you need. There are several factors which can affect this, such as room dimensions, heating levels and types of window, which are all covered in our radiator BTU calculator.  A BTU, short for British thermal unit, is a basic measure of thermal (heat) energy. One BTU is the amount of energy needed to raise the temperature of 1 pound (0.45 kg) of water by 1° Fahrenheit (0.55° Celsius). Re: dougsherman's post. 1 BTU is roughly 1055 joules of heat, or energy. You are mistaking joules with joules/second. Regardless of how long it takes to expose the water to 1 BTU of heat, 1 BTU of heat will raise the temperature of 1 pound of water 1 degree Fahrenheit. BTU is an acronym for British Thermal Unit. Although its name seems to suggest otherwise, it is no longer commonly used in the United Kingdom. BTU is a unit of measurement for energy. One BTU is equal to the amount of energy used to raise the temperature of one pound of water one degree Fahrenheit. In most applications the BTU has been replaced by the joule, but BTU remains a popular measurement of heating and cooling equipment. In a heat pump or furnace, the BTU number refers to the heat output of the particular unit. The higher the number the more heat the unit can produce. Air conditioners are a little different. The BTU number on cooling equipment refers to the amount of energy used to remove the heat from the air. It represents the amount of thermal energy necessary to raise the temperature of one pound of pure liquid water by one degree Fahrenheit at the temperature at which water has its greatest density (39 degrees Fahrenheit). The Btu is a measure in the so-called English system of units (the foot-pound-second system). A British thermal unit (Btu) is a standard unit of energy that is used in the United States and sometimes in the U.K. Mike McCune/Flickr. Definition: A British Thermal Unit (BTU) is the amount of heat energy needed to raise the temperature of one pound of water by one degree F. This is the standard measurement used to state the amount of energy that a fuel has as well as the amount of output of any heat generating device. 
http://homeguides.sfgate.com/average-btu-furnaces-88602.html http://www.bestheating.com/btu-calculator http://www.wisegeek.org/what-is-a-btu.htm https://en.wikipedia.org/wiki/BTU http://www.diy.com/help-advice/btu-radiator-calculator/Dev_npcart_100006.art http://www.wisegeek.org/what-is-a-btu.htm https://servicechampions.com/what-does-btu-mean-for-your-furnace-ac/ http://whatis.techtarget.com/definition/British-thermal-unit-Btu http://bbq.about.com/od/gasgrills/g/gbtu.htm
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