How to plan long-lead equipment orders on a Gantt chart
Plan long-lead equipment on a Gantt chart: place the order early, show the factory wait as its own task, see what site work can proceed meanwhile, and see exactly how much a late delivery moves the finish.
Some equipment takes months to arrive, and the site cannot finish without it. This guide shows how to put the order, the delivery wait and the installation on a Gantt chart so you can see what a late delivery does to the date.
The short version
- Plan the order, the factory wait and the installation as three separate tasks.
- Give the wait the supplier's quoted length in working days, so it can be on the critical path.
- Link the order to what releases it, then test how much an earlier release changes the finish.
- Let site work that does not need the equipment overlap the wait.
- A late delivery is a longer wait task; the dates after it move, and progress never moves dates.
Treat the wait as a task
On many projects the longest item on the schedule is not work your crew does. It is the time between placing an order and the equipment arriving: transformers, inverters, switchgear, turbines. A plan that shows only the installation hides this. The installation task appears to start whenever the crew is free, and nothing on the chart explains why the date does not move when the crew finishes early.
The fix is to give the order, the factory wait and the installation three separate tasks. The order is short and depends on whatever releases it, such as a signed agreement or an approved specification. The wait is a task with the supplier's quoted length in working days. The installation depends on the wait and on the site being ready. Once those links exist, the chart shows which of the two, site readiness or delivery, sets the finish.
This also shows when ordering earlier pays off. If the order waits for a late decision, moving that dependency and reading the new finish date tells you how many weeks the earlier commitment buys, and you can weigh that against the risk of ordering before the decision is firm. A delivery that arrives late is then a change to one task length, and the dates after it move.
The example below builds the solar farm template in stages. Every duration is illustrative, so replace each wait with what your suppliers quote. A timeline schedules the work. It does not make an order binding, an item certified or a connection approved. For the final stages see /guides/commissioning-and-energisation-gantt-chart, and for how links drive dates see /guides/gantt-chart-dependencies.
A solar farm plan with long-lead equipment, built in stages
Twenty-two tasks in four groups. Durations are illustrative; set your own. Open the spreadsheet panel to see the rows behind each stage.
The wait that releases the orders
"Secure site control and surveys" takes 8 working days. "Submit grid connection application" takes 3, then "Utility connection study and offer" is a 35-day wait. "Connection agreement signed" is a milestone that follows it.
Design and the two orders
"Finalise design and equipment specification" (10 days) starts 5 days into the surveys. "Place module order" and "Place inverter and transformer order" take 2 days each and wait for the design and for "Connection agreement signed".
The delivery waits
"Module manufacture and shipping" is 40 working days and "Inverter and transformer manufacture and shipping" is 45. They are waits, not site work, and they start when their orders are placed.
Site work meanwhile, then installation
"Clear site and build roads and fencing", "Drive piles and build foundations" and "Install racking" run without the modules. "Install modules" waits for "Module manufacture and shipping", so racking finishes weeks before it can start. "Install cabling and inverters" waits for the inverters.
Tests, energisation and handover
"Build onsite substation and connection works" runs beside the array. "Run pre-energisation inspection and testing" waits for it and the cabling, then "Site energised", "Run commissioning and performance tests" and the "Handover complete" milestone follow.
Chasing a late order is a loop, not a bar
A Gantt chart has one bar per task and cannot draw a repeating chase. The expediting process is better shown as a flowchart. Open it to see the rows behind each stage.
Check the order against the need date
It starts at "Identify PO approaching required date", then "Request supplier milestone and shipment evidence" and "Compare confirmed ETA with need date". The decision "Delivery at risk?" splits the path.
Recover or carry on
"No" leads to "Continue routine milestone monitoring". "Yes" leads to "Assess inventory and production impact" and "Agree recovery plan or partial shipment". If "Recovery meets critical need?" is no, "Expedite transport or trigger shortage response" returns to the assessment.
Escalate and record
When recovery is enough, "Escalate critical delay and alternate supply" and "Track shipment through receipt" follow, and "Log revised promise and supplier performance" closes the process. On the Gantt chart, allow for the loop by giving the wait task a length that includes it.
How it works
List the items with long lead times
Go through the equipment list and pick the items where the wait is longer than the work around them. Give each one an order task, a wait task and an installation task.
Enter the quoted wait as a duration
Set the wait task to the supplier's lead time in whole working days. If delivery risk is high, add a buffer task after it; see /guides/gantt-chart-buffer-time.
Link the order to what releases it
In Depends on, point the order at the decision, agreement or approved specification that releases it. Point the installation at the wait and at the site work it needs.
Let other work overlap the wait
Link site preparation to its own predecessors, not to the delivery, so it runs beside the wait. Use start-to-start links with a lag where the crew can begin soon behind another task.
Read the critical path and test an earlier order
Switch on the critical path in the View menu to see whether the wait sets the finish. Then change the order's dependency and compare the finish dates; see /guides/gantt-chart-critical-path.
Move the date when delivery moves
When the supplier changes the date, change the wait task's duration. Do not just mark progress, because progress does not move dates. Share the chart and export a PDF for the project file.
Mistakes to avoid
Planning only the installation
If the wait is not a task, the chart cannot show that delivery sets the date. Add the wait as its own task so it can show on the critical path.
Ordering before the decision is firm
An earlier order shortens the plan but commits money before the design or agreement is settled. The chart shows the weeks gained; the commercial risk is yours to weigh.
Trusting a quoted lead time as a promise
A quoted lead time is an estimate. Check it with the supplier at intervals, and when it changes, edit the duration so every date after it follows.
Expecting the chart to draw the chase
A Gantt chart cannot draw a repeat-and-escalate loop. Give the wait a length that allows for it, and use a flowchart for the process itself.
Open the solar farm Gantt chart
Open the solar farm template, change the delivery waits to your suppliers' lead times and see the finish date move.
Related guides
Frequently asked questions
How do I show a delivery lead time on a Gantt chart?
Add a task for the wait, set its duration to the quoted lead time in working days, and make the installation depend on it. The wait then shows as a bar between the order and the installation.
What happens if the supplier delivers late?
Lengthen the wait task. Every task that depends on it moves, and the critical path view shows whether the finish date moves too. Work that does not depend on the delivery stays where it is.
Can I order before the contract or agreement is signed?
The chart lets you change the link and see the date effect. Whether you should order early is a commercial and legal decision that the chart does not make for you.
Does the chart track the supplier's actual shipments?
No. It holds your plan and the dates you enter. Update the wait task's duration when the supplier gives you a new date.
Where do I plan the chase process itself?
In a flowchart. The purchase order expediting process at /templates/purchase-order-expediting-process draws the checks, the escalation and the loop back to the assessment.