When getting a quote from any air conditioning company, ask them if they will be doing a complete manual load Calculation on your house. Recent surveys show that 88% of all ductwork is installed incorrectly, and 92% of systems are not sized properly. https://www.youtube.com/watch?v=4WVsQThJXDY Taking into account the insulation value of your walls, ceilings, and floors, then they do not know what they are doing, and you should consider using another Charlotte NC Air Conditioning company. 2. Ask them how they will be sealing the duct work and the return boxes ( these are the big folded sheet metal box’s that are part of the duct work) If the duct work and box’s are not sealed correctly, you will have air leaks, these will drive up operating costs, and shorten the life of your equipment. And no, duct tape is not a sealant!! There are specially designed tapes and adhesive silicon’s that should be used. Its not uncommon to have up to 30% leakage in an air conditioning system that’s not sealed correctly. 3. Ask if they will be installing dampers on all of the supply line ducts. Without these dampers, it is impossible to evenly balance the temperature in your home, and can lead to hot or cold rooms, which will significantly decrease your comfort. 4. Make sure the company is reputable. Make sure they are insured and accredited. Do not use the first guy who gives you an upfront low price. You will pay for it in the end. 5. Ask about a programmable thermostat. For a small upfront cost you can save you on average $250 a year on an average sized 4 bedroom home. 6. Ask about multiple returns. This will increase the efficiency, and reduce noise level. 7. If you have allergy problems ask about Hepa filtered systems and once again ensure that the entire air-conditioning system is properly sealed. If not you will be allowing all those insulation particles, Dust and other allergens that are in your roof to enter your air conditioning system and be spread throughout your home. 8. Ask if your air conditioning system has a variable speed motor commonly referred to as an Inverter which can significantly increase efficiency and reduce operating costs.