ELI5: How does air conditioning work?

An air conditioner works by soaking up the heat from inside your home and dumping it outside, leaving behind only the cool air.

It does not actually create cold air out of thin air; instead, it acts like a giant sponge for heat.

Think about when you get out of a swimming pool on a warm day. Even if the sun is out, you feel chilly when the wind blows. That is because the water on your skin is evaporating, and as it turns into vapor, it steals the heat from your body. An air conditioner uses that exact same trick, but over and over again using a special liquid called a refrigerant that runs inside metal pipes.

Here is how the continuous cycle keeps your room cool:

• Soaking up the heat: Warm air from your living room is sucked into the indoor unit. The cold liquid refrigerant flows through pipes inside, absorbing the heat from the room's air just like a sponge soaks up spilled water.
• Blowing the cool air back: Now that the heat has been stolen from the air, a fan blows that newly chilled, fresh air right back into your room.
• Squeezing the sponge: The warm refrigerant travels through pipes to the big, noisy box sitting outside your house. Inside this box, a pump called a compressor squeezes the liquid, making it super hot.
• Dumping the heat outside: A large fan blows over the pipes outside, releasing the trapped indoor heat into the outdoor air. If you have ever walked past an outside air conditioning unit, you probably felt that blast of hot air blowing out of it.
• Resetting the cycle: Once the heat is gone, the refrigerant cools down, turns back into an icy liquid, and travels back inside to soak up more heat.