Typically, with any piece of technology, you pump one unit of energy in and you get about one out. That’s just the first law of thermodynamics: energy has to be conserved. But there’s a piece of technology called a heat pump, where for every bit of energy you put in, you get three to five times as much heat out. What wizardry is this? Anna Rothschild investigates the science of heat pumps. [Directed by Kevin Herrmann, AIM Creative Studios, narrated by Pen-Pen Chen, music by André Aires].