There are many household items you would never think of replacing when they are still doing their job. For example, it would be silly to buy a new toaster when yours is still toasting bread just fine. It would seem wasteful to buy a new vacuum when yours is still sucking up dust and dirt. But your air conditioner is a bit different. Just because it is still working does not mean you should not buy a new one. If your air conditioner is 10 years old or older, there are some benefits to replacing it, even if it is still blowing out cold air.
Your old AC unit may run an old refrigerant.
A decade or so ago, air conditioners were made to run with a refrigerant known as R-22. This refrigerant worked well, but it was terrible for the environment and was found to contribute to ozone depletion. It was phased out, and a new refrigerant called R-401A was introduced. If you have an older R-22 AC unit and it develops a refrigerant leak, that will be bad for the planet, and you won't be able to obtain refrigerant to recharge it either. It's best to replace that air conditioner now before it starts leaking, so the refrigerant can be disposed of properly.
Your older AC unit is probably using a ton of energy.
AC manufacturers have been trying to make air conditioners as efficient as possible for decades. But the technology was not as good 10 years ago as it is today. Plus, AC units become less efficient as they age, even if they started off really efficient. Your older AC unit likely uses significantly more power than a new one would use. Upgrading will keep your energy bills down, making it the more affordable choice in the long term.
Your AC unit is probably not protected by a warranty anymore.
Most air conditioners have about a five-year warranty. Your older unit is likely not protected by a warranty anymore, which means you will need to pay for any necessary repairs out of pocket. Who wants unexpected repair bills? When you buy a new AC unit, you can plan for the cost of the purchase in advance. The new unit will be less likely to break down, and if it does break, the warranty should cover the cost of repairs.
Even if your older AC is still cooling, talk to your air conditioning contractor about replacing it soon.