In the hot summer months, sometimes a portable air conditioner is necessary to keep rooms habitable. If you use a window air conditioning unit, be sure to choose a window that's shaded or north-facing. Doing this helps the unit draw in cooler air, which means it uses less energy to blow cool air into your home. And avoid having direct sunlight on it or placing it near heat-generating items like televisions and lamps with incandescent lightbulbs. Anything that produces heat can make the air conditioner work harder.