How does an AC capacitor work?

Capacitors are the heart of your home's air conditioning system, and they're one of the most important components for effective operation. They're responsible for giving your air conditioner the initial jolt of electricity it needs to start running and then for storing extra energy so that you can use it when you need cool air again.

They're not batteries and you shouldn't try to change them yourself.
Your AC uses a lot of power and regularly exceeds the capabilities of your home's wiring to kickstart the motors that run the unit. The capacitor helps to compensate for this by providing a large jolt of electricity that gets the motor started and letting it continue running while storing more for when you need it next.

There are two types of capacitors used in an air conditioning system: the start capacitor and the run capacitor. Most units have both, but there are some that only use one.