If you want the benefits of air conditioning, but you don't have the budget to install central AC, which requires ductwork, there are some alternatives that can provide you with cool air that won't bust your wallet. Here are three systems that can do the job at an affordable price.

Portable AC -- As the name implies, a portable AC unit is an all-in-one unit that you can move to different places in your home or flat. Because it is fully self-contained, you just set it up wherever you want it, plug it in and let the air blow at your desired temperature setting. These are great units for flats where you are not allowed to install central AC or window unit ACs, and they are equipped with exhaust vents in the back that blows hot air. It's usually best to put a portable AC unit near a window so that the hot air can disperse outside your house or flat. You can also buy portable AC units with add-ons such as dehumidifiers, which can be of real value when the humidity level outdoors is high. Portable AC units are sold with different BTUs, which stands for British Thermal Units, and is the measure of how much air can blow through the system. The higher the BTU, the more cool air can blow through the unit.

Window AC -- Window unit ACs are popular in flats, because they don't require a great deal of installation work, and they don't take up valuable living space, which is an issue with a portable AC unit. Window ACs, however, can be unsightly, as the back end of the unit is visible to outsiders. Some apartment superintendents won't allow a window AC unit to be installed on a second floor or higher apartment, because of fears that the window unit could fall and create a liability risk. Window units are the most affordable of the three units discussed here, because they have less components and installation is quicker.

Split System AC -- A split system AC unit is also referred to as a ductless split system, and it consists of a indoor cooling unit that mounts on a wall or ceiling, and an outdoor condenser unit that cools the air that enters your home or flat. But unlike a central AC system, a split system doesn't require ducts, so it's much easier to install and much less expensive as well. Split system AC units are not ideal for a flat unless you have a balcony where the outdoor condenser can be placed, though even with that kind of space the noise from the condenser may prove daunting. Contractors install a split system AC by drilling holes near a window and running cables that connect the indoor and outdoor unit. If you need to cool more than one place in your home, you can buy a zoned split system AC, which features multiple indoor cooling units that you can place in different areas of your home at different thermostat settings.