There are many features to choose from, and you want to be sure it's going to deliver the comfort you need since you will have it for the next 16 years. Here are some tips to get you started:

Consider comfort. Many air conditioning systems include extra features that will dramatically improve your home's comfort. Two-stage systems can run at a high and low stage, so they are quieter and provide a better mix of air throughout the home (no hot and cold spots). Also look for compressor sound blankets and swept-wing fan blades to reduce noise. Imagine not having to raise your voice when the air conditioner kicks on.

Buy the highest SEER. Seasonal Energy Efficiency Ratio - or SEER - is a measurement of the efficiency of your cooling system over the course of a cooling season. The higher the SEER rating, the higher the efficiency - and the more dollars you save on utility bills. Systems purchased to prior to 2006 were mostly in the 8 to 10 SEER range. In 2006, the minimum efficiency became 13 SEER. Today, air conditioners can be as high as 24.5 SEER.

A 13-SEER system is 30 percent more efficient than a 10-SEER system, and a 24.5 SEER system is 145 percent more efficient than a 10-SEER system.

Know the type of system you have. If you have an outdoor section and an indoor section, you have a "split system." This is the most common type of system. The indoor section is the coil box that sits on top of your gas or oil furnace. (Many homeowners think this is part of the furnace when it is actually the indoor section to the air conditioner.) The furnace blower is used to distribute cool air throughout the home. In very hot southern regions, the indoor section is typically an electric furnace or Airhandler. This product has the blower and coil inside a single cabinet.

If you do not have an indoor section, you may have a "packaged' air conditioner. Packaged units are found in select regions and can sit next to the house or on the roof. The packaged air conditioner contains the blower and coil components all within the outdoor section and may even provide gas heat or electric strip heat.

Choose non-ozone-depleting R-410A refrigerant. Most air conditioners ready for replacement use a refrigerant called R-22. In 2010, the new refrigerant standard became R-410A. R-410A is more environmentally friendly than older refrigerants because it does not deplete the ozone. If you currently have an R-22 system, choosing an R-410A replacement means you may also have to replace your line set and indoor coil, but you will be getting the maximum efficiency out of your new system.

Replace more than just the air conditioner. An air conditioner typically has two components - the outdoor section and the indoor section as described above. It may be tempting to replace only the outdoor section in order to save money. But for your system to achieve the efficiency level you're paying for, you need to have a matched system that includes a new indoor coil. Otherwise, your new system is only as efficient as your old coil. Also, old indoor components can negatively impact the performance of your air conditioner, and your new system warranty could be canceled if it was not installed with the proper indoor coil or air handler.