Which factor is noted as a reason for poor performance in residential air conditioning?

The factor noted as a reason for poor performance in residential air conditioning is typically the presence of excessive dust. When air conditioning units accumulate dust, it can obstruct airflow, reduce efficiency, and strain the unit as it works harder to cool the indoor environment. Dust can also settle on components inside the system, leading to overheating and potential failure over time. Regular maintenance, including cleaning or replacing filters and ensuring that dust does not accumulate around the unit, is vital for optimal functioning.

While other factors like humidity levels can also affect air conditioning performance, high humidity typically makes the system work harder to dehumidify the air rather than causing a direct performance drop like dust can. Additionally, units in shade may actually perform better by avoiding heat from direct sunlight, and low electricity rates do not directly impact how efficiently the air conditioning unit operates in terms of cooling capacity.