Final answer:
Heat pumps are less efficient in cold climates due to greater temperature differences which require more work, decreasing their efficiency. Refrigerators typically do not experience this efficiency loss as they function within a more controlled environment.
Step-by-step explanation:
Heat pumps do not work as efficiently in very cold climates because they depend on the ability to transfer heat from outside to inside. This process becomes less efficient with increased temperature differences between the inside and outside.
Specifically, heat pumps are most efficient when there is a small difference in temperature (ΔT) between the heat source and destination; in colder climates, maintaining the necessary ΔT requires more work, reducing efficiency. In contrast, refrigerators are generally unaffected by external temperatures because they exchange heat within a controlled interior environment, not between the inside of a home and the significantly colder outside air.