If your system is old and inefficient, or the repairs are starting to increase in cost and frequency, you'll probably want to consider replacement.  Today, systems are as much as 60% more efficient than those systems manufactured as little as ten years ago. The savings you'll realize in monthly utility costs can help lower your overall investment. In fact, if you plan on financing your purchase, the monthly savings on your utility bill should be considered when determining the actual monthly cost of replacing your system. This offsetting savings may even permit you to purchase a more efficient system.