The Siemens SIMATIC S7-300 ran factories for two decades, so if you still have one in service the question is a practical one: is it really obsolete, how long can you keep it running, and what do you move to when you can't? Here is the short version, with the dates that matter for planning a spare-parts strategy.
Yes - the S7-300 is being phased out
Siemens has published a phase-out roadmap for the S7-300 and the closely related ET 200M I/O family. According to Siemens' product cancellation notices, regular sale of S7-300 CPUs and modules ends in 2025, after which the products are classed as discontinued and are no longer available to order new from Siemens. Spare-parts and repair support is stated to continue for several years beyond that - commonly cited as roughly ten years from the cancellation - but the exact dates depend on the specific article number.
Because the dates vary by part, always confirm the current lifecycle status of your exact MLFB (order number) on the Siemens SiePortal / Industry Mall before you make a buy-or-migrate decision. Treat the timeline below as planning guidance, not a guarantee.
What that means for you in practice
- New S7-300 CPUs and I/O modules are no longer being produced - remaining supply is last-time-buy stock, surplus, and refurbished units.
- Official spare-parts and repair support is time-limited and counting down, so availability will tighten and prices on hard-to-find modules will rise.
- Your existing system keeps working - obsolete does not mean it stops running. It means you should have a sparing or migration plan before a failure forces the decision for you.
What replaces the S7-300
The designated successor is the SIMATIC S7-1500, with the S7-1200 and the distributed ET 200SP covering smaller or remote-I/O applications. The S7-1500 is faster, uses PROFINET as its main network instead of the S7-300's mix of PROFIBUS and proprietary interfaces, and is programmed in TIA Portal rather than the older STEP 7 / SIMATIC Manager.
Two ways to migrate
- Full replacement: swap the whole rack - CPU, I/O and backplane - for an S7-1500 rack, mapping each old module to its modern equivalent. Best for new panel builds or a planned shutdown window.
- Keep your field I/O: replace only the CPU and convert your existing S7-300 I/O racks to ET 200M remote stations over PROFINET/PROFIBUS, since the ET 200M uses the same SM 3xx modules. This avoids rewiring field cabling and spreads the cost over time.
In most cases the existing PLC program can be imported into TIA Portal and converted with limited rework, but always validate the converted logic on the bench before going live.
Not ready to migrate? Keep it running
Plenty of plants will run S7-300 lines for years yet. The realistic strategy is to stock the modules most likely to fail (power supplies, CPUs, the busiest I/O cards) while they are still findable, and line up a sourcing channel for the rest.
We source S7-300 spares and cross-references
Whether you need to keep an S7-300 alive with hard-to-find modules or you are mapping parts to an S7-1500 replacement, send us the Siemens order numbers (MLFB) you need. We source discontinued and obsolete SIMATIC parts through our supplier network and respond within two business days, sharing price and lead time where we have them and a full written quote once our suppliers confirm. We are an independent reseller and not an authorized Siemens distributor - all trademarks belong to their owners.