Pick to light is, in one sentence, a system of lights on the locations that tells the picker where to pick and how many, plus a button to confirm it was done. It moves no goods and replaces nobody: it cuts search time, takes the paper out of the picker hand and leaves every line recorded with a timestamp. It performs very well in one specific case and poorly in several others. This guide explains how it works, which operations justify it, when it does not pay off and what has to be in order before installing it.
What pick to light is, in one sentence
Picture a shelving run where every location has a small light and a display showing a number. When an order arrives, the lights on the locations to be touched come on and the display shows how many units to take. The picker walks over, picks, presses the button and the light goes out. That is all.
What changes compared with a paper list or a radio frequency terminal (RF, the wireless scanner the operator carries) is that the information sits in the location rather than in the hand: no reading, searching for the code, checking the location and only then picking. The picker sees from the head of the aisle where to go.
There is an important side effect too: button confirmation leaves a record of every line, with a timestamp. That turns the system into a data source, not just a visual aid.
How the light and confirm logic works
The loop is always the same, and it is worth understanding before evaluating anything.
The warehouse management system (WMS, the software that administers locations and movements) receives the order and translates it into a list of locations. It lights that list, generally one zone at a time so the picker is not scattered across the building.
The picker takes the quantity shown on the display. If the real quantity differs, because there is less stock than the system believed, they correct it on the module with the plus and minus keys, which raises a discrepancy alert.
On confirmation the light goes out and the system deducts the line. When the last light in the zone goes out, the container moves to the next zone or to the outbound check.
The detail that matters: if confirmation is only a button, the system records that somebody pressed it, not that they picked the right thing. That is why sample checking is not removed.
Which operations does pick to light suit?
It pays off when three conditions hold together, and returns little if any of them is missing.
Many lines per order. The time saved is per line; if the average order carries one or two lines, the saving is marginal against the cost of the hardware.
Few references, with high turnover. Every location needs its own light module, so cost grows with the number of locations. If a large share of the lines comes from a narrow group of references, that group is the natural candidate.
A compact zone. The system is installed on fixed shelving; the more walking there is between modules, the less the advantage shows.
The textbook case is a high-turnover zone, with orders carrying many lines, in a distribution or e-commerce warehouse with a stable assortment. There, pick to light is often among the cheapest improvements available.
When it does NOT pay off
It is worth being explicit, because this sells easily and does not always fit.
Not if your assortment changes often. Every addition or removal means reassigning modules and relabelling; with a fast-moving assortment, the maintenance eats the benefit.
Not if orders carry few lines across many different references. You would light a whole aisle to pick two things.
Not if the real problem is somewhere else. If the bottleneck is replenishment, the order cut-off time or stock accuracy, pick to light does not touch it: it speeds up a process that will wait anyway.
And not as a first measure. If you have not yet arranged locations by turnover or labelled them properly, that work lowers picking time without buying anything, and it is also a precondition for pick to light to deliver.
What has to be in place before installing it
Three things, and none of them is the hardware.
Stable, well-defined locations. The system ties a light to a location; if locations move around or are not labelled, the map goes stale within weeks.
Reliable turnover data. To choose which zone to light you have to know which references concentrate the lines. That analysis is done on the order history, and it often changes the initial idea of where to start.
Integration with the management software. Pick to light decides nothing on its own: it receives the order from the WMS or from the enterprise resource planning system (ERP, the administrative software that handles purchasing, sales and stock). If that integration is not planned for, the project stalls there.
At STOKA all of this is defined in the on-site survey, before quoting. Projects are installed within 3 to 4 months from the purchase order, and most of that time is preparation, not assembly.
What changes in the picker work
The main change is that reading gives way to looking. Mental load drops, search time drops and the learning curve shortens considerably: a new operator can pick in a lit zone almost from day one, without knowing the assortment.
Value recovered time using your actual operating costs and measurements of the tasks that change. Distinguish time available for other work, reduced overtime and expenses that can actually be avoided.
The risk is the opposite one: the picker stops thinking. If the system is wrong, it is harder for anyone to notice. That is why sample checking should stay in place and discrepancy alerts should be reviewed.
How it compares with other ways of guiding picking
Paper: the cheapest and most flexible. It works with low volume and simple orders. It leaves no per-line record and no way of knowing when each item was picked.
Radio frequency (RF): the operator carries a scanner and confirms each pick by reading the code. It is the most versatile option, works anywhere in the warehouse and genuinely verifies the product, not just the location. In exchange, it requires handling the device on every line.
Voice: the system dictates the location through a headset and the operator answers. It leaves both hands free and holds up well in large zones with long walks.
Pick to light: the fastest per line in a compact, dense zone, and the least flexible when the assortment moves.
In practice they coexist: pick to light in the high-turnover zone and RF everywhere else. Choosing a single method for the whole warehouse is usually the mistake.
A good tool for a precise case
Pick to light is not a technology decision: it is an order-mix decision. If your operation has many lines per order, across a narrow group of high-turnover references in a compact zone, it is among the improvements with the best cost-to-result ratio. If the assortment moves often, if orders are short, or if the bottleneck sits upstream of picking, it is not what you need. The right order is always the same: measure, arrange locations by turnover, and only then evaluate hardware.
Frequently asked questions
It is a system of lights and displays installed on the locations of a shelving run. When an order arrives, the lights on the locations to be touched come on and the display shows the quantity. The picker takes the goods, confirms with a button and the light goes out. It moves no goods: it guides the operator and records every line.
When three conditions hold together: orders with many lines, a narrow group of high-turnover references and a compact physical zone. The saving is per line, so with orders of one or two lines it barely shows, and the cost grows with the number of locations to be lit.
When the assortment changes often, because every addition forces module reassignment and relabelling; when orders are short across many different references; and when the real bottleneck is replenishment, the order cut-off time or stock accuracy. In those cases it speeds up a process that will wait anyway.
Inventory accuracy is measured by comparing records with physical stock. Results depend on receiving and dispatch records, location rules, training and controls; software or robots do not guarantee an accuracy percentage.
Stable, well-labelled locations, reliable turnover data to choose which zone to light, and planned integration with the warehouse management system (WMS) or the administrative system (ERP). At STOKA that is defined in the on-site survey; projects are installed within 3 to 4 months from the purchase order.