What unit is used to measure latent heat and the change of state in air conditioning?

The measurement of latent heat and the changes of state, such as the transition of water from liquid to vapor or vice versa, is best expressed in British Thermal Units (BTUs). BTUs quantify the amount of heat energy required to change the temperature of one pound of water by one degree Fahrenheit, making it a practical and widely used unit in air conditioning and refrigeration contexts.

In HVAC applications, understanding latent heat is crucial for managing humidity and temperature control. When a substance undergoes a phase change—like when water evaporates or condenses—the energy involved does not change the temperature of the substance. Instead, it is this energy that influences the moisture present in the air, and BTUs provide a clear measure of that energy during the process.

Other units mentioned have different applications: Pascals are used for measuring pressure, degrees Celsius are a direct temperature measure, and Joules, while also a measure of energy, are less common in HVAC contexts. BTUs are specifically tailored to heating and cooling processes, making them the optimal choice for this measurement.