Heat energy is measured in _________.

Heat energy is measured in BTUs, which stands for British Thermal Units. A BTU is defined as the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit. This unit is particularly relevant in the field of heating and cooling, where it helps quantify energy transfer in systems such as refrigeration and HVAC.

While other units like Joules, Watts, and Calories are also related to energy and thermodynamics, they serve different purposes. Joules are a more general measure of energy rather than specifically heat. Watts measure power, which is the rate at which energy is used or transferred, not the amount of heat itself. Calories are a unit for measuring heat energy, often used in food energy contexts, but BTUs are more common in HVAC practices. Therefore, BTUs is the most appropriate answer when discussing heat energy in the refrigeration and heating context.