Every maintenance operation runs somewhere on a spectrum between two approaches: fixing things when they break, or servicing them on a schedule to prevent failures. Neither is purely right or wrong — but the tradeoffs are significant, and most teams that rely entirely on reactive maintenance are paying more than they realize.
Definitions
Reactive maintenance (also called corrective maintenance or “run-to-failure”) means waiting for a failure to occur before acting. Something breaks; you fix it. There’s no advance planning, no scheduled servicing — the failure event itself is the trigger.
Preventive maintenance (PM) means servicing equipment on a predetermined schedule — by calendar interval, runtime hours, or usage cycles — before failures occur. The goal is to catch wear, lubricate moving parts, replace consumables, and identify developing problems while they’re still cheap to address.
A third approach — predictive maintenance — uses sensors and condition monitoring to service equipment only when data indicates it’s needed. This is more sophisticated and requires investment in instrumentation; it’s worth knowing the term, but most small and mid-size teams start with time-based PM before considering predictive.
The Real Cost Difference
Industry data consistently shows that reactive maintenance costs three to four times more per event than planned preventive maintenance. The reasons compound:
- Emergency labor costs more. Overtime, after-hours call-outs, and rushed diagnostics all carry a premium.
- Parts procurement under time pressure is expensive. You buy from whoever has the part overnight, not whoever has the best price.
- Secondary damage. A failed bearing that ran dry can ruin a shaft, a housing, and nearby components. A $20 grease job at the right interval would have prevented a $2,000 repair.
- Production downtime. In manufacturing environments, unplanned downtime typically costs far more than the repair itself — because the line is down.
- Technician context switching. Every emergency repair pulls a technician off something they were already doing. The interrupted work either gets delayed or done sloppily.
None of this means reactive maintenance is always avoidable. It means that the more you rely on it, the more you pay.
When Reactive Maintenance Is Acceptable
Reactive maintenance is a rational choice for some equipment. The criteria:
- Non-critical. If this asset fails, work can continue without it, or the failure can be tolerated until a scheduled repair window.
- Cheap to replace. If the cost of a PM program exceeds the cost of just replacing the item when it fails, PM isn’t worth it.
- Failure mode is obvious and quick to fix. Light bulbs are the classic example — most teams don’t “preventively maintain” fluorescent tubes; they replace them when they burn out.
- Redundancy exists. If a backup system can absorb the load during a failure, the urgency of preventing that failure is lower.
The mistake most teams make isn’t running reactive maintenance on light-duty, non-critical equipment — that’s fine. The mistake is running reactive maintenance on critical production equipment because the PM program was never set up.
Building a PM Program
Step 1: Start with Critical Assets
Don’t try to preventively maintain everything at once. Start with the assets that have the highest consequence of failure: production bottlenecks, safety-critical systems, equipment with long lead times for parts or service, and anything that has already caused costly downtime.
A simple criticality ranking helps. For each major asset, score it on two axes: likelihood of failure (based on age, condition, and history) and consequence of failure (impact on production, safety, and cost). Assets that score high on both get PM schedules first.
Step 2: Set Frequencies Based on Manufacturer Guidance and History
Manufacturer recommendations are the starting point for PM intervals. They’re conservative by design — most can be extended once you have failure history to support it. If you have no history, start with the manufacturer’s recommendation and adjust over time.
If you have existing failure data (even rough records), look at how often an asset has historically required corrective work. That tells you the natural failure interval. A PM interval set at roughly half the typical failure interval is a reasonable starting point.
Step 3: Build Checklists, Not Just Tasks
A PM work order should contain a checklist, not just a description like “service HVAC unit.” A useful checklist specifies:
- Replace air filter (note the filter size and part number)
- Check belt tension and condition
- Clear condensate drain
- Inspect electrical connections
- Record refrigerant pressure readings
The technician who completes this task may not be the one who designed the procedure. Checklists capture institutional knowledge and make PMs auditable.
Step 4: Assign Ownership and Track Compliance
Every PM schedule needs an owner — a person or team responsible for completing it. PM compliance rate (the percentage of scheduled PMs completed on time) is one of the clearest indicators of a maintenance program’s health. If you’re not tracking it, you don’t know whether your PM program actually runs.
A CMMS with preventive maintenance scheduling handles the triggering and assignment automatically — PMs appear in the queue on schedule without anyone having to remember to create them.
Common Mistakes When Implementing PM
Setting intervals without data. Choosing a monthly schedule because it sounds right, rather than because failure history or manufacturer guidance supports it, leads to either over-maintaining (wasting time and money) or under-maintaining (still having failures).
Writing PM tasks that are too vague. “Check HVAC” is not a checklist. Technicians will interpret it differently every time. Specificity is what makes a PM procedure transferable.
Ignoring PM completion data. If PMs are being closed in the system but the underlying failure rate isn’t changing, either the procedure is wrong or the work isn’t being done correctly. PM compliance rate and MTBF should move together.
Trying to PM everything at once. A realistic PM program covers the most critical assets and expands as capacity allows. A 40% PM coverage rate that’s actually running beats a 90% coverage rate that’s always behind.
Not revisiting schedules. A PM interval that was right two years ago may not be right today. Equipment ages, usage patterns change. Review PM frequencies annually against actual failure data.
Practical: How to Identify Which Assets Need PM
A criticality assessment doesn’t have to be elaborate. For each major asset, answer these questions:
- What is the likely consequence if this asset fails unexpectedly? (Score 1-5: 1 = inconvenient, 5 = production stops or safety risk)
- How frequently has this asset required unplanned repairs in the past? (Score 1-5: 1 = rarely, 5 = several times per year)
- Is there a backup or workaround if this asset is down? (Yes = lower priority, No = higher priority)
Total the scores. Assets at the top of the list get PM schedules first. This process takes an afternoon for a typical facility and gives you a defensible, data-informed starting point.
For more on PM terminology and how it connects to reliability metrics, see the preventive maintenance glossary entry.