Utilisation time: how much of the clock you actually choose to use

A facility runs one eight-hour shift, five days a week. The equipment inside it is immaculate: it rarely breaks down, it makes good product, and whenever it runs, it runs well. On every maintenance measure, the team is doing its job.

The calendar tells a different story. Across the year, the asset was scheduled for fewer than a quarter of the hours it could have worked. Nothing is broken and nothing is being done badly, yet most of the asset's life is being spent switched off. Utilisation time takes that uncomfortable fact and puts it into a single percentage, so the business can see, plainly, just how much of an asset's potential it is actually choosing to use.

What it actually measures

Utilisation time is the share of all available calendar time that an asset is scheduled to operate.

You work it out by taking idle time out of the total available time, then dividing by that total. Put simply: of every hour the clock offered, how many did you actually put the asset to work? It is the very first link in the capacity chain, and it feeds straight into total effective equipment performance. Before you can sensibly ask whether an asset ran well, you have to ask whether you chose to run it at all.

How to work it out

Utilisation time = (Total available time - Idle time) / Total available time × 100

Take a full year of 8,670 available hours, of which the asset sat idle, unscheduled, for 2,890.

Utilisation time = (8,670 - 2,890) / 8,670 × 100 = 66.7%

Two-thirds of the year was scheduled; the other third was idle by design. Whether that is fine depends entirely on the business. If demand only calls for two-thirds of capacity, the number is simply honest. If demand could fill more, this is the gap to close before anyone signs off on new capital.

What good looks like

There is no universal target, because the right figure is set by your market and your operating model, not by a benchmark book. As a rough guide, utilisation in a typical plant runs somewhere around 60 to 80 per cent of the calendar, while world-class operations push it into the 85 to 95 range, but a plant serving a thin or seasonal market will sit lower for perfectly sound reasons. What matters is the trend, watched over time and by class of asset. A rising line means growing demand or sharper scheduling; a falling one is worth understanding before it turns into a financial question.

Where the utilisation losses hide

When utilisation is poor and demand is not the reason, the cause is often buried in how the plant chooses to run. The classic culprit is product mix. In many operations a small handful of products earns the overwhelming majority of the sales, while a long tail of rarely ordered items earns almost nothing, yet every one of them is offered on the same responsive schedule. The result is a line forever stopping a profitable run to slot in a tiny order, and a culture of never losing a sale that quietly shreds effective utilisation. Looking hard at the tail, and at how often you interrupt long runs for short ones, is frequently where the hidden hours are.

The opposite lesson is just as useful. The objection that "this asset runs almost around the clock, we are far too busy to maintain it" usually means utilisation is being managed badly, not that it is genuinely maxed out. Plants built with a little flexibility, parallel cells rather than one critical line, can stand a unit down when demand dips and use exactly those freed hours for maintenance. Hospitals, airlines and railways all manage to maintain equipment that is in constant demand; a plant that claims it cannot is usually describing a scheduling problem, not a law of nature.

Where it can mislead you

• Utilisation time is driven by forces well beyond maintenance: demand, raw materials, labour, margins, strategy. Never use it to judge the reliability or maintenance team.
• A high utilisation time sitting next to a low availability is a red flag. The asset is being asked to run almost constantly but cannot keep up, which accelerates wear and leaves almost no window to maintain it properly. That combination tends to end in exactly the breakdown nobody had time to prevent.
• Report it annually. Shorter windows get distorted by seasonal demand, planned shutdowns and short-term scheduling quirks.
• Read it with availability and TEEP, never alone. Utilisation tells you how much you scheduled; the others tell you how well those scheduled hours actually went.

Utilisation time is the foundation every other capacity conversation stands on. It says nothing about how well the asset performs, and it is not meant to. It answers the question that comes first: of all the time you could have put this asset to work, how much did you choose to? Until you know that, no other number about the asset can be read in its proper light.