There are all kinds of air conditioning systems. Most of them are really effective at keeping your home cool and comfortable. All of them, however, require installation, and each has its own level of "mess" attached to installation. In order to decide which new system you want, here are the systems in order of least to most mess for AC installation.

Window Units

Pop it in, pop it out. Seal around the expanding accordion-side pieces to keep bugs out and prevent cool air from escaping. Your biggest mess is the constant draining down the side of the house, and all of the spiders and bugs you have to clean off the unit when you pull it out of the window in the fall.

Ductless Units

A single compressor outside has to be installed. Hoses and wiring run into the house to the areas where the wall mount components are hung. A single hole is drilled into each wall where a wall mount is to be installed. Hoses and electrical wiring are either sent down or up through the holes to connect the compressor with the wall mounts. Done.

Heat Pumps

Heat pumps take up almost as much space as central air conditioners. They also utilize your home's forced air system to pull hot air out (or put it back in, depending on your heat pump type and season of the year). That means that a level concrete slab goes outside and acts as a base for the pump's compressor and condenser. Wiring and other components go through a hole in the side of the house to connect to your ventilation. The biggest part of the mess is the concrete slab and hole drilling through your siding.

Central Air

Central air has one major unit box outside, an added fuse box to boost power to the evaporator and condenser in the outside box, and a hole through the siding to connect to your electrical box, furnace, and vent system inside. Lots more holes to drill, lots more parts to connect. However, central air units, when properly cared for, last longer than all of the previously mentioned systems. (So maybe the concrete slab and extra holes are worth it?)

Geothermal

Geothermal units are expensive, but only because they create the most mess and require the most labor to install. A large cylindrical hole is dug vertically, or a long, elliptical, horizontal hole is created to install "the loop." Dirt is piled up during excavation, and holes are drilled through your concrete foundation to a box inside your basement, crawl space, or utility closet. When the whole process is complete, most of the piled dirt goes into the hole to bury the loop, except for the extra dirt that is displaced by the geothermal loop.