Most residential central air conditioners are split-systems because they have an outdoor condensing unit / compressor and an indoor Air Handler / Furnace with an evaporator coil. The air handler/ furnace is wired to move more air in the cooling season and less air during the heating season since it is harder to cool a house than it is to heat it. Most new construction is designed on a 20 degree T.D. (temperature differential) which means that when it is 100 degrees out side the indoor temperature will be 80degrees. I have found that in Texas it is more satisfactory to use a 30 degree T.D.

High-efficiency air conditioners, those with an SEER rating of 16-23 will cost more initially and will result in lower energy bills, however, unless your home is properly insulated and has double pane insulated windows you will probably never realize the maximum savings on your utility bill. Most high-efficiency air conditioners have a two-stage compressor, which operates on demand, as the load increases or decreases and they all use the more environmentally friendly R-410A refrigerant.

New central air conditioners must have SEERs (seasonal energy efficiency ratings) of at least 13 you can often buy a central air conditioner with Mid-range efficiency (14.5 to 17 SEER) without having to pay more. The mid-range air conditioners use R-410A refrigerant instead of the standard R-22.

Low-efficiency air conditioners, those with a 13-14.5 SEER are still considered highly efficient compared to the standards in place 10 years ago.if you're replacing an old model, even a low-efficiency unit will lower your electricity rates considerably. If you're on a tight budget then this air conditioner is probably your best choice overall.

If you have a large house you should consider zoning it, installing two smaller units in place of one large unit. Choose the rooms where you spend most of your time and have one unit dedicated to those areas. Also, if one unit should go out, you will still have one unit that is working until you can have the necessary repairs made.

If you are replacing your old condensing unit with a new one be sure to have your evaporator coil replaced also or you will not realize the potential savings and your unit will not be as efficient as it should. Also make sure that your Air Handler/ furnace is capable of delivering the specified cfm that it is designed to deliver. All the fancy bells and whistles won't mean anything if you don't have enough air volume to move the air where you. need it.