How is the energy efficiency ratio (EER) calculated?

The energy efficiency ratio (EER) is calculated by taking the cooling output of an air conditioning system, measured in British thermal units per hour (Btuh), and dividing it by the input power, measured in watts. This ratio provides a measure of how effectively the cooling system converts energy into cooling output.

In essence, a higher EER indicates a more efficient air conditioning system, as it means more cooling output is produced for each watt of electrical input. This metric is crucial for consumers and professionals assessing the efficiency of HVAC systems, helping to make informed decisions about energy consumption and operational costs.

The other options do not accurately represent how EER is defined or calculated, as they either confuse units or mix concepts that do not relate directly to energy efficiency measurement in this context.