Machines & Inventions

How can a heat pump move warmth from cold air into a house?

Because a circulating refrigerant absorbs heat outside and releases it once it's compressed. Even cool outdoor air holds a surprising amount of hidden warmth. A refrigerant evaporates at a low temperature and soaks some of that heat up. A compressor then squeezes it hotter, and indoors, that warmth is released before the refrigerant heads back outside to start again.