What aspect of a window unit makes it less effective for larger spaces?

The cooling capacity of a window unit is a critical factor that determines its effectiveness in a given space. Window air conditioning units are designed for smaller areas, and their cooling capacity—measured in British Thermal Units (BTUs)—is generally lower compared to central air conditioning systems or larger units specifically designed for bigger spaces.

When a window unit is placed in a larger area, it is likely that the cooling capacity will not be sufficient to effectively cool the entire space. This means that while the unit may efficiently cool the immediate area directly around it, it will struggle to maintain comfortable temperatures throughout the larger room, leading to uneven cooling and potentially increased energy usage as the unit runs longer to try to meet the demand.

Other aspects listed, like noise level, energy efficiency, and installation complexity, may impact user experience or convenience, but they do not directly influence the fundamental ability of a window unit to effectively cool a larger area. Thus, the primary limitation of window units in larger spaces is indeed their cooling capacity.