There are many ways to measure energy. One of the basic measuring blocks for energy is called a “BTU,” standing for British thermal unit. A BTU is the amount of heat energy it takes to raise the temperature of 0.45 kilograms of water by 0.56 degrees Celsius, at sea level. One BTU equals the heat generated by about one blue-tip kitchen match. One thousand BTUs are roughly equivalent to the energy your body receives from eating an average candy bar.