The heat pump is the most efficient air conditioning device that exists. It does not consume electricity to generate heat or cold, but to move the heat from one place to another, it does so by taking advantage of certain laws of physics. Refrigerators are heat pumps, as well as air conditioners. Mechanically, they convert the liquid from their interior hydraulic circuit to gas; the gas is located where we want to extract the heat; a compressor -which consumes electricity-, pressurizes the gas, with a double result: when compressed, the gas becomes liquid again. This change of state produces heat, which we introduce where it suits us.