Which of the following is not a recognized unit of energy?

Watt is indeed a unit of power, not energy. Power is defined as the rate at which energy is used or transferred over time, typically measured in joules per second, while the watt itself quantifies this rate. In contrast, the other options are all recognized units that measure energy.

For example, kilowatt-hours (kWh) is a common unit used to quantify electrical energy consumed over time, such as in home electricity bills. A quad is a larger unit often used in energy statistics, representing one quadrillion (10^15) BTUs. The calorie is primarily used in the context of heat energy, especially in the dietary field or thermodynamics, where it reflects the amount of energy needed to raise the temperature of one gram of water by one degree Celsius. Each of these units effectively measures energy, while watt conveys a different concept related to the rate of energy consumption or production.