While the lifespan of a new AC unit varies based on make and model, most will last between 10 and 15 years. Some systems, however, can last over 20 years if properly maintained. A lot of this, however, depends on how much you use your air conditioner. That doesn’t mean, however, that you should wait for it to break. Old units are often inefficient and expensive to repair. Being proactive about AC replacement is a great way to save money on your utility bills.