Siemens S7-300 Discontinued: What It Means for Your Plant

In many plants it has been running for twenty years or more, reliably and unobtrusively: the SIMATIC S7-300. It controls presses, filling lines, wastewater treatment plants and conveyor lines. The maintenance team knows every module, the programs have grown over time, and the spare parts sit on the shelf. Or used to.

Then comes the news that the S7-300 has been discontinued. Some react calmly (“it’s still running”), others in a panic (“we have to rebuild everything right now”). Neither is usually the best response.

This article puts into context what the discontinuation of the Siemens S7-300 means, which components are affected and how you can reach a sound decision for your plants in three steps.

What exactly has happened?

Siemens moved the SIMATIC S7-300 and the ET 200M distributed I/O to lifecycle status PM410 on 1 October 2025. PM410 means product discontinuation. This milestone was originally planned for 1 October 2023 and was postponed.

Since this step, the products are no longer supplied as new products for new installations, only as spare parts. For existing plants, this means: the S7 300 keeps running, and under the discontinuation status spare parts are in principle still provided for. How long individual items remain available, however, has to be checked for each article number, not assumed across the board.

Discontinued does not mean “no longer available”

The most common misconception: discontinued is confused with “unavailable from today”. In fact, discontinuation describes a phase in the lifecycle. The product is no longer intended for new installations, but the supply of spare parts to existing plants continues for the time being. What changes is planning certainty. The further the lifecycle progresses, the more important it becomes to have a strategy. You will find the basics in the article Obsolescence management for discontinued spare parts.

Which components are affected?

The S7-300 system as a whole is affected. This includes:

• CPUs of the S7-300 family
• Input and output modules, digital and analogue
• Communication modules
• Technology modules, for example for counting or positioning
• Accessories for the system
• ET 200M interface modules of the distributed I/O

So for your assessment, it isn’t just the CPU that counts. A plant with an S7-300 CPU and several ET 200M stations is affected in many places.

The successors: S7-1500, S7-1200, ET 200MP and ET 200SP

Siemens names the S7-1500 as the successor to the S7-300. For smaller applications, the S7-1200 is an option. For distributed I/O, the ET 200MP and ET 200SP replace the ET 200M. The successors are programmed in the TIA Portal.

For maintenance, this means: switching to the S7-1500 is not a module-for-module swap. The existing program has to be migrated to the TIA Portal and adapted for the new hardware. How much effort that takes depends heavily on the size, structure and documentation of the program. On top of that come hardware configuration, wiring, communication with other systems and recommissioning.

Three strategies for existing plants

Strategy	When it makes sense	What you need to do
Continued operation with spare parts stocking	plant runs stably, remaining service life is limited, a failure is manageable	identify critical modules and stock them selectively, keep the program backup up to date
Step-by-step migration	several plants, limited shutdown windows, budget spread over several years	set the order by criticality, migrate during planned shutdowns
Complete migration	plant is to keep running for a long time, a modification or expansion is planned anyway	project with planning, program migration, commissioning and documentation

In practice, many companies combine these approaches. The most important plant is migrated, while smaller plants continue running with spare parts stocking until a modification is due anyway.

Step 1: take stock

No overview, no decision. For each plant with a SIMATIC S7-300, record:

1. All modules with their complete article number and, where visible, product or firmware version.
2. Quantity per type across all plants. Common parts are a lever for stocking.
3. Existing spare parts in the store, with condition and storage location.
4. Program status: is there an up-to-date, commented backup that matches the version in the plant?
5. Interfaces: which systems does the controller communicate with, such as operator panels, the control system or other controllers?

For each article number, then check the current lifecycle status and spare parts availability in Siemens Industry Online Support under the product lifecycle information. The status for each item is recorded there. Don’t rely on blanket statements, nor on dates you have heard second-hand.

Step 2: assess the risk

Not every S7-300 is equally critical. Ask three questions for each plant:

• What does downtime cost? Is a central line affected or an ancillary plant?
• How much longer is the plant meant to run? One, five or fifteen years?
• How well is the plant understood? Are there in-house specialists who understand the program, and is the documentation up to date?

A plant with high downtime consequences, a long planned remaining service life and thin documentation belongs at the top of the migration list. An ancillary plant that will be replaced in a few years anyway can often manage with selective stocking.

Typical scenario: two lines, two paths

A company has two filling lines with an S7-300. Line A is the heart of the operation and is meant to run for many more years. Line B will be replaced by a new machine in the foreseeable future. For line A, the company plans the migration to an S7-1500 during the next major shutdown. For line B, the critical modules are stocked, including the CPU, power supply and the most heavily loaded output modules. Both decisions are right, because each suits its plant.

Step 3: secure spare parts and plan the migration

If you continue operating

• First stock the modules whose failure stops the plant immediately, usually the CPU, power supply, communication modules and heavily loaded I/O modules.
• Pay attention to the product or firmware version. A spare CPU should match the project.
• Check spare parts in the store regularly for completeness and condition, and keep memory cards and backup batteries ready where your CPUs use them.
• Back up the program after every change and store the backup separately from the plant.

If you migrate

• Plan early, not after the next failure. A migration project under time pressure is expensive and error-prone.
• Use planned shutdowns for the conversion.
• Keep removed, working S7-300 modules. They can serve as spares for plants that have not yet been migrated.
• Update circuit diagrams, spare parts lists and the program archive after the migration.

For how to stock spare parts systematically by criticality, see also the checklist Control Cabinet: 10 Spare Parts You Should Always Keep in Stock.

Typical mistakes in dealing with the discontinuation

• Waiting until something fails: then a decision you could have planned becomes an emergency.
• Looking only at the CPU: I/O, communication and ET 200M modules are just as affected.
• No up-to-date program: without a backup that matches the plant’s current state, neither a module swap nor a migration is safe.
• Taking blanket dates at face value: availability has to be checked per article number.
• Installing untested spare parts: with spare parts from other sources, pay attention to origin, condition and the correct product version.

How to recognise a usable spare part

The further the lifecycle progresses, the more often modules come from different sources. That makes looking at each individual part all the more important. At goods receipt, check at least these points:

• Article number: does it match the order completely, digit by digit?
• Product version: does it suit your project, or does the hardware configuration need to be adapted?
• Condition: housing, connectors and contacts free of damage, corrosion or signs of overheating.
• Packaging and labelling: traceable origin, labelling and nameplate unaltered.

Where possible, fit a spare module once on a trial basis during a planned shutdown. Then you know in advance whether it will work when it matters.

What to include in an enquiry

For S7-300 modules, the complete article number is decisive, i.e. the full number beginning with 6ES7, including every digit. Add the product or firmware version, a photo of the device labelling, the quantity required and whether a different product version is acceptable. The checklist for spare parts enquiries summarises the key points.

When modules become scarce

Discontinued controller modules often need more than one sourcing channel. KTB Europe is a family business from Hamburg and has been sourcing industrial spare parts of all brands worldwide since 1976. Send us the article numbers of your S7-300 components, a nameplate photo or a list from your inventory. We source the parts and inspect them in our own central warehouse. If a part can no longer be obtained, we look for alternatives.

Find out more on our pages on discontinued parts and spare parts management. You can send your enquiry via the contact page.

Conclusion

The Siemens S7-300 has been discontinued since 1 October 2025 and is now only supplied as a spare part. For existing plants, this is no reason to panic, but it is a clear reason to plan. Record your installed base, check availability per article number, and assess each plant by risk and remaining service life. Then make a deliberate choice between continued operation with stocking, step-by-step migration to the S7-1500 or S7-1200, and a complete changeover.