What does one British thermal unit (Btu) measure?

One British thermal unit (Btu) specifically measures the heat energy required to raise the temperature of one pound of water by one degree Fahrenheit. This definition is rooted in the field of thermodynamics and provides a standardized method for quantifying energy. The measurement of Btu is crucial in various applications, including heating, cooling, and energy consumption calculations.

This definition captures the fundamental concept of a Btu as a unit of heat, making it essential for understanding energy transfer in heating systems, cooking, and other thermal processes. The other choices, while they might relate to energy in some contexts, do not accurately describe the specific focus of one Btu. Understanding this measurement allows for better comprehension of energy demands in residential and commercial energy contexts, linking it to system efficiency and energy usage when evaluating home energy ratings.