When it comes to keeping cool in your home, you’ve got options – four, actually. Whatever you choose (or happen to already have in your home), all air conditioning systems share these five common traits: a refrigerant, compressor, condenser, expansion valve and evaporator coil.

Below, we’ll discuss what defines each type of air conditioning system and how they work. Which type of air conditioning system do you have?

1. Window Air Conditioner

Window air conditioners are literally the total package. The unit contains all the air conditioning components, including the evaporator, cooling coil, compressor, condenser and expansion coil or valve. For a simple solution to your cooling problems, window air conditioners are it!

Window air conditioners have a pretty obvious drawback, and we’ll just go ahead and say it: they’re kind of ugly. But if anything is going to help you come to peace with the clunky aesthetics, it’s the cost-savings: because these units allow you to cool a single room – namely, the one you’re in at the time – you’ll spend less over the short and long term.

2. Split Air Conditioners

Divide and conquer. That’s the motto of the split air conditioner. The unit divvies up the work of cooling one or two rooms between its outdoor and indoor components. On the outdoor side of things, you’ve got the compressor, condenser and expansion valve, whereas indoors you’ll find the evaporator coil and cooling fan.

3. Packaged Air Conditioners

Say you’ve got a bigger cooling job than just a room or two, and a window air conditioner or split air conditioner just won’t do. In cases where you need to cool down multiple rooms or large, open spaces, a packaged air conditioner is definitely the better choice.

These units are arranged in one of two ways. First, a single box can contain the various components (a compressor, condenser, expansion valve and evaporator). Once air is cooled down in the packaged air conditioner, it is then sent to each room through the ductwork.

In the second case, it’s individual units, each with their own expansion valve and cooling coil, that do the cooling. These are located in the rooms you want to cool. The compressor and condenser are contained in one unit.

4. Central Air Conditioners

As air conditioning systems go, this is “the big one”. It’ll cool your offices, your hotels, your larger buildings, your homes in their entirety. A giant compressor does most of the work. Cool air from the air conditioning unit gets pumped throughout the structure through ducts and out of registers (openings in walls, ceilings and floors, often covered by a metal gate).