WARNING – Read this article before buying a new and efficient air conditioning system
When you start to get the price, buy a new central air conditioning system, and most HVAC companies will try to tell you that you are more efficient High level = higher utility savings.
Unfortunately, most of the time this is not true because the higher the efficiency the larger the coil. The larger coil limits the airflow that makes the fan more hard.
If your pipeline project is designed to handle this limitation, then this is not a problem, but it is rare.
The National Comfort Institute and the Department of Energy's study found that the capacity of most residential piping systems was 55%.
Adding a larger coil to a poorly performing system will actually increase your utility costs instead of reducing them.
This will also make the compressor and fan motor work harder and break.
Therefore, your new central air conditioning system is not concerned about the brand and efficiency level, but attention to the entire system of contractors. If you let a contractor enter your house, check the static pressure of your existing system, and then his advice sounds like what he says. I bet he knows the airflow well, and how every part of the family comfort system adapts to family comfort and operational efficiency. 
Than To spend your money to improve your distribution system and standard 13 SEER system install a super efficient air conditioner in a bad piping system.
It is a good idea to do both of these budgets, but if you have to choose your the best return on investment, it will be in a well-designed Sealed Piping Systems
Most families can reduce costs by 45% by making sure that your pipe's work size is appropriate, sealed and balanced.
A good heating and cooling contractor will do the following for you .  
- A complete assessment of the family and existing equipment
- Ask any problem areas that you are dissatisfied with existing systems, utility costs
- ] Static pressure reading of existing systems.
-  Prefabricated Heat Loss and Thermal Gain Load Calculation
- A good contractor will also be Determine the airflow required for each room.