What does the energy efficiency ratio (EER) in HVAC measure?

The energy efficiency ratio (EER) is a crucial metric in the HVAC (Heating, Ventilation, and Air Conditioning) industry, specifically designed to measure the efficiency of cooling systems. It is calculated as the ratio of a unit's cooling capacity, expressed in British Thermal Units (BTUs) per hour, to its power consumption in watts. This ratio essentially indicates how effectively a cooling system converts electrical energy into cooling energy—higher values of EER reflect better energy efficiency.

This measurement is vital for consumers and professionals in assessing how much cooling output can be expected from a system relative to its energy use. By focusing on cooling capacity and energy consumption, EER provides a clear snapshot of operational efficiency, enabling informed decisions regarding purchasing and operating HVAC equipment.

The other options do not align with the definition of EER. Specifically, measuring total energy consumed to heating output pertains more to seasonal efficiency measurements rather than the EER, which is about cooling. The EER does not apply exclusively to heating systems, and it also does not address the performance of ventilation systems, which are separate components of HVAC systems. This focus on cooling capacity relative to energy consumption makes option C the correct choice for what EER measures.