What’s with these cheap air conditioners?

Those bargain boxes, reader, are more accurately known as evaporative coolers or, perhaps even more accurately, as swamp boxes. They’re an application of age old science: the phase transition of liquid water to vapour does tend too cool the air around it a bit. But don’t expect miracles. They’re far inferior to refrigeration-based coolers, particularly in the cheap tabletop form that seems to be covering the market right now, and not really much more effective than putting some cool water near a fan – which is essentially what they do.

Bear the swamp portion of them in mind, too; they’re damp, increase the humidity of the room they’re used in, and can get themselves and anything moisture-sensitive in your room pretty gross in a short amount of time. They’re sort of opposite to modern AC, in that way. Guru isn’t about to suggest you don’t use one if it’s the only possible way to get some relief from the heat, but don’t expect miracles.