Repair side
A well-defined localized fault, good remaining condition and available parts can support repair.
Replacement side
Major failure, repeated unrelated faults, obsolescence, incompatible systems or a safety-driven change can support replacement.
Uncertainty should be visible
If no one knows the cause yet, do not pretend a replacement comparison is complete.
Cost comes after comparable scope
Repair and replacement figures should include the work needed to produce equivalent usable results.
Safety boundary. General planning information only. Do not open, dismantle or work on hazardous electrical, gas, structural, fire-protection or contaminated-water systems unless you are appropriately qualified and authorized.