What does 'boiler efficiency' measure?

Boiler efficiency specifically measures how effectively a boiler converts the energy in fuel into useful energy in the form of steam or hot water. It is expressed as a percentage and indicates how much of the energy content of the fuel is effectively utilized for producing heat and steam, as opposed to being lost to the environment. A higher boiler efficiency means that a greater portion of the energy from the fuel is being used effectively, which often correlates with reduced fuel consumption and operational costs.

In contrast, maintaining a boiler involves ongoing costs but does not directly relate to how well the boiler converts fuel to energy. The amount of steam produced per hour, while important for operational capacity, does not reflect the efficiency of the energy conversion process. Additionally, emissions levels, while relevant for environmental concerns and regulatory compliance, also do not measure the effectiveness of the energy conversion. Therefore, the key focus of boiler efficiency lies in this conversion effectiveness, making the chosen answer the most accurate representation of what boiler efficiency measures.