What does "boiler efficiency" measure?

Boiler efficiency measures the effectiveness with which a boiler converts the energy in fuel into useful energy output, typically in the form of steam or hot water. This concept is represented as the ratio of useful energy output to the total energy input, which illustrates how much of the energy consumed by the boiler is actually converted into useful work, as opposed to being lost as waste heat. A higher efficiency indicates that the boiler is using the fuel more effectively, resulting in lower fuel costs and reduced emissions.

The other options do not accurately define boiler efficiency. For example, the amount of water boiled per hour is a measure of the boiler's capacity, not its efficiency. The temperature of the steam produced indicates the thermal characteristics of the output but does not reflect how efficiently the boiler operates. Similarly, total fuel consumption speaks to the amount of fuel used but does not convey how effectively that fuel is converted into energy. Thus, defining boiler efficiency in terms of the useful energy output relative to energy input is essential for evaluating and optimizing boiler performance.