The two costs everyone adds up
When people compare corrective and preventive maintenance, they almost always compare two things:
- The technician’s time. An emergency repair is paid at emergency rates, often after hours.
- The spare part. In a breakdown you buy it in a hurry, without negotiating, from whoever has it in stock.
That alone usually makes a breakdown more expensive than the equivalent inspection. But it is the easy part of the math.
The five costs almost nobody adds up
- Downtime. What you stop producing or billing while the equipment is out of service. In manufacturing it is usually the biggest cost, and it rarely shows up in any spreadsheet.
- Unplanned travel. The technician drops what they were doing and drives across the county. That trip also wrecks the plan for the rest of the day.
- The domino effect. The inspection that got skipped to handle the emergency causes next month’s breakdown. Corrective work feeds on itself.
- Diagnosing blind. Without the equipment history, the technician starts from scratch. With it, they often arrive knowing what to check, with the part already in the van.
- The customer. A breakdown that stops their operation costs credibility, and sometimes the renewal. It is the hardest cost to put a number on and the most expensive one over two years.
Why preventive work still gets dropped
Because it competes at a disadvantage. The emergency has someone on the phone demanding a fix now; the scheduled inspection has nobody speaking up for it. Three causes keep coming back:
- There is intent, but no schedule. If preventive work does not create a work order with a date and an owner, it does not exist.
- Postponing costs nothing. If nobody records that an inspection was pushed back, it gets pushed back again.
- Nobody measures it. Without the corrective-to-preventive ratio in plain sight, nobody notices things getting worse until it is obvious.
When corrective maintenance is the right call
Not everything should be preventive. Running to failure makes sense when any of these is true:
- The asset has low criticality: its failure does not stop anything important.
- It can be replaced quickly and cheaply, with the spare on hand.
- Inspecting it regularly costs more than replacing it when it fails.
A light fixture does not need a maintenance plan. It needs someone to change the bulb when it burns out. The goal is not “zero corrective.” It is deciding which equipment gets preventive care and which runs to failure. Many companies never make that decision: they simply react.
How to run the numbers with your data
Five steps. A spreadsheet is enough to start:
- Pick one family of equipment, not the whole fleet.
- Pull the work orders from the last 12 months.
- Add up hours, parts and travel for the corrective ones.
- Estimate the cost of the inspections that would have prevented them, and how many of those failures they would really have caught.
- Add the cost of downtime, even as a rough estimate. It is usually the number that decides the result.
Example
A family of pumps had 24 failures in a year. Each one meant 6 hours of downtime at $250 an hour, plus $900 in repairs.
Corrective: 24 × (6 × $250 + $900) = $57,600 a year New plan: 48 inspections × $150 = $7,200 a year If it prevents 7 of the 24 failures: 7 × $2,400 = $16,800 saved
In this example, the plan pays for itself once it prevents three failures a year. These figures only show the math: use your own.
The conclusion is often uncomfortable. It is not that preventive maintenance is cheap. It is that, until now, nobody had the data to know.
Three mistakes when comparing
- Using the price of an inspection instead of its real cost. An inspection also means travel, materials and the time to document it.
- Assuming preventive work prevents everything. There are random failures, impacts and misuse. Count only the failures an inspection would have caught.
- Forgetting about findings. An inspection that spots a problem and does not create a corrective work order has prevented nothing.
The KPI that sums it up
The corrective-to-preventive ratio is a good gauge of how a maintenance operation is doing. Measure it in hours: corrective hours divided by total maintenance hours.
There is no universal good number. The trend, however, tells the truth. If corrective work climbs month after month, the plan is falling apart, even if nobody has said so out loud.
Review that ratio with your team every month. It is a short, cheap conversation, and it heads off a lot of expensive ones.
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