The answer to 'when to replace AC' is that you should typically replace your air conditioning unit every 10-15 years, or when it becomes inefficient and costly to repair. As AC units age, they become less energy-efficient and more prone to breakdowns, leading to higher utility bills and repair costs. Factors like the unit's age, performance, and repair history can all indicate when it's time to consider a replacement.
Older AC units that are over 10 years old and require frequent, expensive repairs are often good candidates for replacement. You may also want to replace your unit if it's no longer keeping your home comfortable or if your energy bills have been steadily increasing. Upgrading to a newer, more energy-efficient model can save you money in the long run through lower utility costs and reduced maintenance.