The answer to 'when to replace HVAC repair' is that you generally need to replace your HVAC system every 15-20 years, depending on the type of system and how well it has been maintained. Factors like the age of the system, frequency of repairs, and energy efficiency can all indicate when it's time to replace your HVAC rather than continue repairing it.
As HVAC systems get older, they become less efficient and more prone to breakdowns. Once your system reaches 10-15 years old, you'll likely need to start budgeting for a replacement in the next 5-10 years. Frequent repairs, high energy bills, and inconsistent temperature control are all signs that replacement may be the better long-term solution.