Planned Downtime (discounted downtime)

Not every minute a machine is stopped should count against it. Breaks, shift changes, planned maintenance and other scheduled stoppages are outside the operator's control, so counting them as "unavailable" would unfairly drag down the OEE score.

To handle this, every stopped slice of the machine timeline is classified into one of three downtime categories. Planned downtime — also called discounted downtime — is the category that is excluded from OEE entirely.

The three downtime categories

When the machine is not running (stopped or off), each slice of the timeline falls into one of three buckets:

Category	Effect on Availability
Unproductive downtime	Counts against the score (avoidable stoppage)
Productive downtime	Counts as good time (e.g. setup, tool change)
Planned / discounted downtime	Neutral — removed from the calculation

The category comes from the downtime reason assigned to the stoppage. A reason configured as discounted produces planned downtime; see downtime reason configuration for how reasons are set up.

How planned downtime affects Availability

Recall that Availability is, where downtime means all stopped-but-monitored time (productive + unproductive + planned) and offtime means the machine was off or reporting no data:

operating time          = uptime + productive downtime
planned production time  = uptime + downtime + offtime − planned downtime
Availability             = operating time ÷ planned production time

Planned downtime is subtracted out of the denominator. That means the time never appears in the calculation at all — it neither helps nor hurts the score. The machine is judged only on the time it was expected to be producing.

Compare this to the other two categories:

• Unproductive downtime stays in the denominator only, so it lowers Availability.
• Productive downtime is added to the numerator and the denominator, so it is treated as good, producing time.
• Planned (discounted) downtime is removed from the denominator, so it is treated as if the machine was never scheduled to run.

A worked example

Over an 8-hour window a machine records:

• 5 hours uptime
• 1 hour productive downtime (a tool change)
• 1 hour unproductive downtime (an unexplained stop)
• 1 hour planned downtime (a scheduled break)

Here downtime (all stopped time) is 1 + 1 + 1 = 3 hours and offtime is 0:

operating time         = 5 + 1                = 6 hours
planned production time = 5 + 3 + 0 − 1        = 7 hours   (the break is removed)
Availability            = 6 ÷ 7               = 86%

Without the discount, that break would have stayed in the denominator (5 + 3 + 0 = 8 hours) and pulled Availability down to 6 ÷ 8 = 75%. By classifying it as planned downtime, the hour is excused and the machine is scored only over the 7 hours it was genuinely expected to run.

Where it applies

Planned downtime only affects Availability. Performance and Quality are driven by cycle times and part counts, not by the timeline, so they are unaffected. Because OEE is Availability × Performance × Quality, correctly discounting planned stoppages keeps the whole OEE score fair.