There are three types of unit air conditioners you should consider: window unit, built-in window and split system.
* Window unit: The window unit is (usually) easy to install into any standard double-hung window. It should offer multiple cooling options (low-high). This is the kind that most people get because it's the cheapest; you just stick it in a window and hope it doesn't fall on anyone below. Weight: approximately 120 lbs.
* Built-in window: The built-in window again can be installed into any standard double-hung window, or it can even be installed right into your wall. This unit offers heat/cool and cooling with heat pump features, as well as the standard cooling options. It's fancier than the standard window unit and it does more stuff, but it also usually consumes more energy (leading to higher electric bills). Weight: approx. 90 lbs.
* Split system: The split system provides an outside air compressor option for quiet cooling. (This type won't unexpectedly hiss at you, causing you to drop your coffee in your lap.) But these almost always have to be professionally installed, adding to the cost. Weight: approx. 70 lbs.
All of the above types are typically run at 115 Volts or 230/208. Either will work just fine in almost any outlet. Select the type that best accommodates your needs and the type of room in which it will be located. Most people find that the window unit is plenty.
