When you need a fast solution on a hot day, a window air conditioner seems like the best solution. You simply affix the unit in the frame of your window, seal off the drafts, and you can have a room cooled down in no time at all! This type of air conditioner is perfect for a single room flat, a small apartment, or a room that needs to be cooled down on its own. Look for an air conditioner that has a 1.5 ton minimum capacity for the most effective solution and compare models such as the Carrier EsTrella to get the most energy efficient model. If you are looking for a more powerful air conditioning solution, then a Split A/C unit may be a better choice. These units have the ability to cool down multiple rooms and install through a window or sealed exterior vent to pull in the cool air. Many of these units are much more energy efficient than other air conditioners, so they can save you in the long term even though most of them are more expensive than a window unit. Look for brands like Samsung, Panasonic, or Sharp to compare specific features and capacities.