Which is a common feature of energy-efficient HVAC systems?

A common feature of energy-efficient HVAC systems is low noise levels. This feature is accomplished through advanced design and technology aimed at reducing operational noise while enhancing performance. Energy-efficient HVAC systems often utilize variable speed motors and carefully engineered ductwork and components, allowing for quieter operation.

In addition to being more energy-efficient, these systems are designed with user comfort in mind, prioritizing not only performance but also minimizing disturbances from noise, which contributes to a more pleasant indoor environment. This characteristic is particularly important in settings where noise can be distracting, such as in residential and office buildings.

In contrast, high energy usage, manual temperature control, and constant speed fans do not illustrate energy efficiency. High energy usage is contradictory to the principles of energy efficiency. Manual temperature control can lead to inefficiencies and discomfort, while constant speed fans do not adjust their output based on demand, which can result in unnecessary energy consumption and increased noise levels.