Generally, all forms of energy are measured in terms of joules in the SI system. Notably, heat is a form of energy, and therefore the SI unit of heat is also joules (J) which are defined as the amount of energy needed to raise the temperature of a given mass by one degree. The SI unit of heat energy is a joule. Explanation: The unit of heat in the SI system is the joule (J) and the calorie (cal) in the CGS measurement system. The heat required to raise the temperature of one kilogram of water by 1 °C from 14.5 °C to 15.5 °C is called one kilocalorie of heat. Unit Of HeatUnit of Heat SI Unit of Heat The SI unit of heat is the joule (J). It is named after James Prescott Joule, a British physicist who made significant contributions to the study of thermodynamics. The joule is defined as the amount of energy transferred or work done when a force of one newton is applied over a distance of one meter in the direction of the force. Here are some examples of how the joule is used to measure heat: When you turn on a light, the electrical energy from the ... The SI unit of heat is Joules (J) which is the same as the unit of energy as heat is the form of energy.