What unit is used to measure energy?

The British Thermal Unit (BTU) is indeed a unit used to measure energy, specifically the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. It is commonly used in HVAC applications to quantify heating and cooling energy.

In the HVAC industry, using BTUs is practical because it relates directly to the energy content of fuels and the performance of heating and cooling systems. For example, air conditioning units or heaters are often rated in BTUs, providing a clear understanding of their energy output and efficiency.

While joules, watts, and calories are also units of energy or power, their applications differ. Joules are the standard unit of energy in the International System of Units (SI), while watts measure power (the rate of energy transfer). Calories are commonly used in chemistry and nutrition to measure the energy content of foods. Therefore, when specifically discussing energy in the context of HVAC, the BTU is the preferred and most relevant unit.