Single-stage units operate at a fixed output level, delivering heating or cooling in an on/off fashion. Known for its simplicity and affordability, it runs at full capacity whenever activated and then shuts off until the next call for heating or cooling.

They are generally less energy-efficient compared to more advanced models, and their simplicity may result in temperature swings and less precise control. Despite these limitations, single-stage units are a cost-effective option for budget-conscious homeowners seeking basic heating or cooling functionality.