Look for federal tax credits or utility rebates for energy-efficient (SEER2) units.
If your furnace is also aging, you can often get a significant discount by replacing both the heating and cooling systems at once. When's the Best Time to Buy a New AC Unit? best month to buy air conditioner
Buying in the last week of any month can yield better deals as sales teams push to meet monthly goals. Look for federal tax credits or utility rebates