How To: Buy an Air Conditioner

How To: Buy an Air Conditioner

Gregory Han
Aug 5, 2009

It is that time again, and we've got a friend who wants an air conditioner and who has asked our advice in regards to picking out an air conditioner. Although air conditioners are horrible to look at, for many of us who call a rental or an apartment home, they're practically a necessity, so we try to recommend designs with the most innocuous presence as possible balanced with performance. Since our friend has two really nice windows in the room in question, our first bid was for a portable AC that would only require a white hose to run out the bottom of one of the windows...

While researching we discovered that portables tend to be expensive and don't have the same cooling ability as a window unit, and so we backed away from that solution for budget reasons. We had a DeLonghi Penguino years ago that worked perfectly well in our small apartment, but it did require some work and only cooled one room. We decided, therefore on the window unit, and this is what we found:

How does it work?
Air conditioners work in similar to that other cool appliance in your home, the refrigerator. Instead of cooling just the small, insulated space inside of a refrigerator, an air conditioner treats your whole room like a fridge cools it's interior.

Here's the process broken down to the basics from HowStuffWorks:

  1. The compressor compresses cool Freon gas, causing it to become hot, high-pressure Freon gas (red in the diagram above).
  2. This hot gas runs through a set of coils so it can dissipate its heat, and it condenses into a liquid.
  3. The Freon liquid runs through an expansion valve, and in the process it evaporates to become cold, low-pressure Freon gas (light blue in the diagram above).
  4. This cold gas runs through a set of coils that allow the gas to absorb heat and cool down the air inside the building.

What to look for?
A good Energy Star rating, remote control, easy to install, form factor (slimmer profile less decor intrusive), energy-saver mode and timer.

What are good sites for reviews and research?

  • (membership required)

What is the best unit?
Depends upon the size of your room, as a unit should be chosen in relation to the dimensions of the room being cooled. Too powerful of a unit and you're wasting energy, too small and you won't feel the relief of cooler air, and thus are wasting energy again.

Also, whether you want a unit you can easily put away. Although portable units are more expensive than window units, prices have dropped low enough in the last few years to make them viable options for people who want to have the option to move around or store away the AC when not in use.

How big do you need?
You need approximately 35 BTU's per square foot to cool a room with a normal ceiling (8-10'). So find your square footage and multiply by 35. If your room is 10' by 15' = 150 sq. ft. you multiply by 35 = 5250 approximately a 5000 BTU machine.

How much will it cost?
Air conditioners are very competitively priced. For a very good machine, you should expect to pay around $250 for a small AC (5000 BTU), $450 for a medium AC (8000 BTU), and $800 for a big one (up to 24000 BTU). There is a wide range of prices, part of which depends on features which include timers and remotes. Installation should run you about $100.

Note: by choosing an Energy Star certified you might be qualified for a rebate or federal tax credits for energy-efficient improvements. We received a $50 rebate for our ENERGY STAR qualified room air conditioner via the Los Angeles DWP, and other states have similar programs. See how much you can receive in rebates at

Where do I buy?
Sears (we have the Kenmore 75062 and love the slim profile, Energy Star performance)
Portable AirShop
Air & Water Inc.

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