What unit is used to measure the quantity of heat energy?

The correct choice for measuring the quantity of heat energy is British thermal units (BTUs). A BTU is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit at a constant pressure. This unit is particularly useful in various heating, cooling, and energy applications, making it widely recognized in the fields of heating, ventilation, and air conditioning (HVAC).

While joules also measure heat energy and can be an acceptable answer in other contexts, BTUs are more conventional in the HVAC industry, particularly in the United States. Watts, on the other hand, are measurements of power (the rate of energy transfer) rather than heat energy itself, and cubic feet measures volume, not heat.