[pandaman]

The special liquid is running through a system of tubes, called "coils" so it could exchange heat with the air. Keeping comfortable temperatures inside is also a function of the inside coil's temperature, which depends on the special liquid and the compressor. The higher temperature difference between the inside and outside coils, the higher compression is required and lower is the COP. Incidentally, the high inside coil's temperature is also required to heat the air inside at a reasonable rate.

[out_of_protocol]

technically speaking, you can crank up internal fan speed to eleven and get exhaust temperature slightly above current room temperature even if internals are way too hot. regular resistive heaters do that, with their heating elements fired up way past boiling water temperature

[pandaman]

The problem is not the exhaust being too hot, but the heating element being too cold. Gas furnace, for example, burns gas at temperatures much higher than that of boiling water.