Final answer:
An air conditioner is most efficient when the temperature difference between the inside and outside environments is small, leading to a better coefficient of performance (COP) and less required work input for heat transfer.
Step-by-step explanation:
An air conditioner will work most efficiently when the temperature difference (ΔT) between the inside and the outside is small. This is because heat pumps, which include air conditioners, are most efficient when they don't have to work as hard to maintain a large temperature difference. When placed in a hot environment, like a garage, an air conditioner has to work harder, and this leads to reduced efficiency—this is the 'double-whammy' effect. For example, in moderate climates, where ΔT is not extreme, heat pumps have a higher coefficient of performance (COP), indicating better efficiency.
Air conditioning units function on the principle of transferring heat from a cooler space to a warmer one. This requires work input, and the more work that is needed, the less efficient the process becomes. Therefore, a better COP is achieved when less work is required for a given amount of heat transfer. The performance of air conditioners is often assessed through this COP ratio, which prefers conditions where the device does not have to invert a large ΔT to cool a space.