Heat pumps work at >100% thermal efficiency.

Air conditioners dont.

An air conditioner is a heat pump… That just works in one direction. It uses refrigeration just the same.

They both rely on creating a thermal gradient between two heat exchangers. And they are both negatively affected by extreme temperature gaps.

The heat exchanger facing outside with a heat pump must be colder than ambient temperature by a reasonable margin. The opposite goes for an AC. These qualities break down in extreme ranges for typical hardware.

This also, as expected, reduces the efficiency.