OptimalOEE™ Wiki / Understanding OEE
Theory
Understanding OEE
Overall equipment effectiveness measures how well an asset runs against its own potential, in a single percentage. It is the product of three independently measured factors, and its power is that a weakness in any one pulls the whole number down.
The idea
Take the time a machine was scheduled to make good product at full speed. Strip out the time it was stopped, the speed it lost while running, and the units it made that were not good. What remains is fully productive time, and OEE is that as a fraction of the scheduled time. It reduces a messy shift to one honest number, and to three factors that each point somewhere different.
The three factors
| Availability | Run time as a share of planned production time. Lost to breakdowns, changeover overruns and waiting. The maintenance and reliability factor. |
|---|---|
| Performance | Actual output against the theoretical maximum at design speed. Lost to minor stoppages, reduced-speed running and idling, often masked by operators nursing poor equipment. |
| Quality | Good units as a share of total units produced. Lost to defects, rework and startup rejects. Equipment condition and process stability are the primary drivers. |
Because OEE is a product, the factors are not interchangeable. An 85% in each gives about 61% overall, so knowing which factor is low, and why, is what tells you where to act.
Benchmarks
Published benchmarks vary, so read them honestly. Across large multi-plant datasets most lines sit well below the textbook 85%:
| 50–70% | Typical real-world OEE in many industries, and a realistic first target for most sites. |
|---|---|
| 85% | The classic world-class benchmark, from about 90% availability, 95% performance and 99.9% quality. Rare, and not the right first goal for most lines. |
| Above 90% | Deserves scrutiny. Legitimate in a few continuous or highly automated sectors, but often a sign the time base, speed baseline or count has been set softly. |
A benchmark is for direction, not a trophy. A believable from-source number you can act on beats an impressive one you cannot defend.
OEE, TEEP and utilisation
OEE measures the scheduled time only. Total effective equipment performance (TEEP) extends it by a utilisation factor, the scheduled time as a share of all calendar time, so TEEP asks not just how well you ran, but how much of the available clock you scheduled at all. OEE is the operational lever; TEEP is the capacity lever.
Measurement is not the cure
An OEE dashboard that does not trigger a structured response is an expensive reporting exercise. OEE is a symptom; reliability is the cure. OptimalOEE™ is built so the number is explainable to the raw reading and points straight at the losses, so the maintenance and reliability interventions that actually move it are obvious. Next, the losses themselves.