An expandable, mobile structure is capable of sustaining a retracted state and an expanded state, and may be capable of alternately using public utilities as a power supply, or a self-contained “off-grid” power supply. This allows for use of the mobile structure in a multitude of locations, which are not governed by the presence or absence of an available external power supply. The structure may operate in an “on-grid” power mode when in an expanded condition, and in an “off-grid” mode in a retracted condition. The structure includes a different number of zones within the structure in the retracted state as compared to the expanded state. A modular HVAC system provides a different flow path of air in the retracted state and the expanded state.