If you have an AC unit that is twenty years old or older, then you are overpaying to cool your home. The reason for this is twofold: 1) Machines wear out over time, and as they do, their maintenance suffers. 2) Newer machines are held to a higher standard of efficiency. Replacing your old AC unit, with a new highly efficient model will help to get your cooling costs back on track, but in order to realize the full potential of your AC system, you need to improve your home's insulation envelope and have your duct system inspected for leaks.
Windows are a perennial weak spot in a home's insulation envelope. While triple-pane windows will help to prevent hot outside air from getting into your home, they will do nothing to prevent UV rays from streaming in. Once inside, these UV rays will heat up the interior surfaces and walls of your home. The hotter your home gets, the harder your AC system has to work to cool it back down. To prevent UV rays from driving your cooling costs up, you need to have your windows coated with a Low-E window film. You can buy some new windows that have the coating already installed, or you can add film to your already existing windows. The right film can reduce your cooling costs by up to 23%.
As cold air moves through ducts in the summer and hot air during the winter, the ducts are subjected to a constant cycle of expansion and contraction. Over time, this can cause the mastic that prevents leaks at the joints and seams in your duct system to dry out and crack. These cracks can then allow air to leak out of your ducts and decrease your overall system efficiency by up to 40%. Thus, when you install a new AC system, you should have your ducts inspected and any leaks thus discovered repaired in order to make sure you realize the full potential of new AC unit.
If you are replacing an older AC unit in order to reduce your cooling costs, you need to remember that the AC unit is only one component of your home's defense against heat gain. Your home's insulation envelope is the first line of defense in preventing heat gain. Upgrade as needed to prevent as much heat gain as possible. Inspect and repair all components of your AC system to make sure there are no other problems. Companies like Universal Refrigeration may be able to help.