BTU meters measure energy change in liquid or gas flows. One BTU is 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). This is equivalent to approximately 1055 joule (or 1055 watt- seconds). Natural gas BTU represents the amount of energy generated by burning one volume of natural gas. A BTU meter is a portable meter. On supplying power to the BTU meter, alphanumeric characters in two separate lines are displayed on the screen. Next, consecutively press and release the supply and return temperature buttons to display the temperature variation in the form of cycle. After successfully displaying the temperature lines, verify them for their correctness. There are many types of BTU meters. Examples include a furnace and energy meter. A BTU furnace is used for raising the temperature of one pound of water by a single degree Fahrenheit. An energy meter is a three phase meter for measuring, recording, and displaying energy consumption. Other BTU meters are commonly available.