A failing heating or cooling system always seems to break at the worst possible time, and the repair-or-replace question is stressful. A few clear signs tell you when you're throwing good money after bad.
Consider the age
Most central air conditioners and heat pumps last around 12–15 years, and furnaces a bit longer. If your system is in that range and needs a major repair, replacement is often the smarter long-term move — and newer units are far more energy efficient.
Watch repair frequency and cost
One repair is normal. Repairs every season are a pattern. A common rule of thumb: if the repair cost multiplied by the unit's age in years tops about $5,000, lean toward replacing. Two big repairs in a couple of years is a strong signal on its own.
Rising bills and uneven comfort
Climbing energy bills with no change in usage, rooms that never quite get comfortable, excess humidity, or a system that runs constantly all point to a unit losing efficiency. A modern, properly sized system can noticeably lower bills and improve comfort.
Old refrigerant is a red flag
Older air conditioners use R-22 refrigerant, which has been phased out and is now costly to source. If your system relies on it and springs a leak, that alone can tip the math toward replacement.