A BTU, or British Thermal Unit, is one of the basic units of measurement for heat energy. By definition a BTU is the amount of heat that is need to increase the temperature of one pound of water by one degree Fahrenheit. The measurements are measured at its heaviest point. So for example, one BTU is needed to heat 16 ounces of water that has the temperature of 59 degrees Fahrenheit to 60 degrees Fahrenheit. To make the water boil, the stove will have to make more BTUs by increasing the amount of fuel that the flame will feed on.
Another way to look at BTU is based on calories. A BTU is equal to 252 heat calories. It should be noted that this is different from the kilo-calories that is associated with food. A BTU is also not entirely confined to heat. In fact, BTUs can also be used in cooling systems. For example, an air conditioning system’s power is based on the amount of heat energy that is sucked out or removed from an area. What this means is that a 55,000 BTU heater and an air conditioner with the exact level of BTUs will have the same capacity and size. The higher the output of the BUT, the more powerful is the system for either heating or cooling.
The BTU is a bit of a misnomer. Even though it is called a British Thermal Unit, this unit of measurement is not often used in Great Britain anymore because it is considered a non-metric measurement.