Siemens S7-1200 vs S7-1500: How to Choose, Down to the Exact CPU and Genuine Part Number

Picking the wrong controller costs money in two directions. Over-specify, and you pay for performance and software licenses your machine will never touch. Under-specify, and you hit a scan-time or I/O wall mid-project, which means rework or unplanned downtime after the line is already running. The Siemens S7-1200 vs S7-1500 decision is where most OEMs, integrators, and procurement engineers get stuck, because the two series overlap just enough to make the choice feel like a coin flip.

This guide ends that coin flip. It does not stop at "the 1200 is compact, the 1500 is powerful." It takes you to the exact CPU and 6ES7 order number, to the real total cost including software, and to a step almost nobody covers: how to confirm you are buying genuine Siemens hardware and not a repackaged fake. If you already know the basics and just need to know which to choose and what to order, keep reading.

Quick Verdict

If you want the answer before the evidence:

• Choose the S7-1200 if your machine is around or below 100 I/O points, needs basic PID and positioning, runs stand-alone or as a small skid, and you are cost-sensitive.
• Choose the S7-1500 if you need fast deterministic scan times, coordinated multi-axis motion, SIL 3 / PL e safety in the controller, redundancy, or plant-scale I/O with rich diagnostics.
• Use both together (an S7-1200 as a PROFINET I-Device under an S7-1500 line controller, with ET200SP distributed I/O) when your machine ships into a plant standardized on the 1500.

Want a part number instead of a series? Jump to the sourcing section, or send us your I/O list and we will map it to an exact CPU.

S7-1200 vs S7-1500 at a Glance: Full Specs Comparison

The Comparison Table

Numbers vary by specific CPU, so treat these as the practical range across each family.

Two corrections, because competing articles get them wrong. First, the S7-1200 has built-in PROFINET as standard; you do not need an add-on module just to program it or put it on Ethernet. Second, "S7-1200" now spans two hardware generations, the original (G1) and the newer G2, which changes the motion and safety picture (covered below).

How to Read the Table

Do not read every row equally. Work memory sets how large your program can be and how many technology objects you can run, and it is usually the first ceiling a 1200 hits. Instruction time and IRT only matter if your process is genuinely high speed; if it is not, 1500-class speed changes nothing on the floor. The software row is a hidden cost driver, not a footnote, because it decides your engineering license. Safety and redundancy rows are pass/fail: either your application requires them or it does not.

S7-1200: What It Is Actually Built For

Where It Is Strong

The 1200 is Siemens' compact controller for stand-alone machines and basic to mid-range automation. Its built-in digital and analog I/O means many small machines need no expansion at all, so the panel stays small and the bill of materials stays low. It runs on the low-cost STEP 7 Basic, ships with a built-in web server for simple remote status, and in the G2 generation adds more memory and motion at the same footprint. For a full hardware teardown, see our S7-1200 CPU Technical Deep Dive.

Its Real Limits

Knowing where it stops matters more than the feature list. Work memory is finite, so large programs outgrow it. STEP 7 Basic does not give you S7-Graph or STL. Motion is basic positioning, not coordinated interpolation. There is no PROFINET IRT and no R/H redundancy. When any of three signals appears (synchronized motion across several axes, deterministic IRT communication, or controller redundancy) the 1200 has reached its edge and you should be pricing a 1500.

Common CPUs and Order Numbers

Representative original-generation CPUs, DC/DC/DC variant:

Order numbers change with the power and output variant (DC/DC/DC vs AC/DC/Relay), so confirm the exact suffix before buying. Worked example: a 12-pump booster station running level control and staged pump sequencing fits on a CPU 1215C with an SM 1231 analog input module, using the controller's built-in PID. No 1500 required. The wider feature picture is in our Ultimate Guide to the Siemens S7-1200.

S7-1500: When Performance and Scale Pay Back

Where It Is Strong

The 1500 earns its price in specific situations. Bit instruction times reach the low nanosecond range on high-end CPUs, work memory scales into tens of megabytes, and every CPU carries a front display and detailed diagnostics that shorten commissioning. It supports PROFINET IRT for isochronous control, T-CPU variants for camming, gearing, and simple kinematics, F-CPU variants for SIL 3 / PL e safety inside the controller, and R/H CPUs for redundancy.

When It Is Overkill

It is easy to over-buy. On a small stand-alone machine with modest I/O, no high-speed motion, and no safety rating, the 1500's performance is wasted and its mandatory STEP 7 Professional license adds cost with no return. Reaching for a 1500 "to be safe" on a simple skid is the most common way to quietly inflate a budget.

Common CPUs and Order Numbers

The main families are 1511, 1513, 1515, 1516, 1517, and 1518, each with standard, F (fail-safe), and T (motion) variants, plus R/H redundancy models. Order numbers use the 6ES75xx prefix and vary by firmware and variant, so the exact suffix should always be confirmed against your configuration. Representative large application: a multi-axis line with coordinated motion, in-controller safety, and distributed ET200SP I/O, where a 1500 (often a T or F variant) is genuinely cost-justified.

The Dimensions That Actually Decide the Project

Performance and Scan Time

The question is not "which is faster" but "does my process need it." High-speed packaging, fast acquisition, or tight loops can justify 1500-class speed. General machine sequencing does not. Verdict: default to the 1200 unless a specific process step demands deterministic millisecond control.

I/O Capacity and Expansion

Around the 100 to 128 point mark you cross from "comfortable on a 1200" into "plan for a 1500 with distributed I/O." Verdict: below that line the 1200 is the economical answer; above it, the 1500 scales cleaner.

Communication and Protocols

The 1200 covers PROFINET, Modbus TCP, and OPC UA natively, which handles most connectivity. Reach for the 1500 when you need PROFINET IRT, richer OPC UA server capability, or heavy IIoT and cloud data. Our S7-1200 communication protocols guide covers the 1200 side in depth. Verdict: native protocols rarely force an upgrade; determinism and scale do.

Motion Control

Basic point-to-point positioning is fine on a 1200. Once you need several axes moving in coordination with camming or gearing, the 1500 with a T-CPU is correct. Verdict: one or two simple axes stay on the 1200; coordinated multi-axis moves to the 1500.

Functional Safety

A 1200F covers lower safety classes. When your risk assessment calls for SIL 3 / PL e or safe motion, the 1500F handles it inside the controller and lets you drop external safety relays, simplifying wiring and cost. Verdict: the required SIL/PL level decides this one outright.

The Third Option Nobody Mentions: Run Both Together

S7-1200 as an I-Device Under an S7-1500

You can configure an S7-1200 as a PROFINET I-Device subordinate to an S7-1500 line controller. The machine keeps its own program and autonomy while the 1500 collects data, coordinates, and manages the line above it. An OEM shipping three 1200-based machines into a plant standardized on a 1500 does not have to re-platform anything; the machines stay on 1200s and report upward cleanly.

Standardize Distributed I/O on ET200SP

The companion move is standardizing field I/O on ET200SP regardless of which CPU sits on top. Because the same I/O family works with both series, your controller choice is never locked in by your I/O, and you can scale or swap the head-end later without rewiring the field. For machine builders selling into varied plant standards, this architecture is often the lowest-risk answer.

Total Cost of Ownership: The CPU Sticker Is the Small Number

Hardware Price Range

The 1200 CPU carries a lower base price than a comparable 1500. Treat any figure as a range that depends on variant and configuration, not a fixed number.

The Software Licensing Reality

This is the layer that flips the math. The 1200 can be engineered on the low-cost STEP 7 Basic, while the 1500 requires the considerably more expensive STEP 7 Professional. On a small project, choosing a 1500 means paying twice, once in hardware and again in the license, for capability you may not use. That single line often outweighs the CPU price difference.

Safety, Gateway, and Lifecycle Cost

An F-CPU can replace external safety relays. Native OPC UA can replace an add-on gateway. A controller typically lives 10 to 15 years, so spare-parts availability and support horizon belong in the calculation. A cost-sensitive OEM building many units almost always wins with the 1200, because savings multiply across the fleet. A long-life plant running critical, safety-rated processes often finds the 1500 cheaper over the full lifecycle. Want a TCO run against your project? Send us the machine details.

Migration and Lifecycle: Coming from S7-300, or Scaling Up Later

S7-300 End of Delivery and Migration

The S7-300 has reached end of delivery, with spare-parts and support running to 2033. The standard migration target is the S7-1500, which inherits the performance-class role the 300 used to fill. A 1200 can suit smaller machines being modernized, but plant-scale 300 systems generally move to the 1500.

Code Portability Between 1200 and 1500

Standard LAD and FBD logic and most technology-object work port over with reasonable effort, but constructs like S7-Graph and STL do not transfer cleanly and need rework. Plan any migration with a real checklist: inventory the code, flag the non-portable blocks, map I/O to ET200SP where useful, and validate safety functions separately. If your comparison is actually one tier lower, our Siemens S7-200 vs S7-1200 guide covers that step of the ladder.

S7-1200 G2: What the New Generation Changes

Key Improvements and Whether They Change the Verdict

Siemens announced the S7-1200 G2 at Hannover Messe 2024, its first new controller generation in a decade, available from winter 2024. The G2 brings more processing power and memory, integrated machine safety, NFC-based diagnostics, and coordinated multi-axis motion with simple kinematics at the compact tier. It requires TIA Portal V20 or higher, and earlier versions cannot connect to it. The practical effect: G2 narrows part of the gap that used to push buyers straight to a 1500 for light coordinated motion or integrated safety, but it does not replace the 1500 for high-end performance, IRT, or redundancy. Because supply is still transitioning between generations, confirm current availability and the correct generation before ordering.

A Decision Framework You Can Actually Run

The Six-Question Checklist

Skip the gut feeling and answer these with numbers.

1. I/O count? Comfortably under ~100 favors the 1200; well over it favors the 1500 with distributed I/O.
2. High-speed scan needed? Deterministic millisecond-class control counts toward the 1500.
3. Motion axes? One or two simple axes: 1200 or G2. Several coordinated axes: 1500 T-CPU.
4. PROFIBUS or legacy support? Heavy legacy integration nudges toward the 1500.
5. Safety level? SIL 3 / PL e in the controller means 1500F.
6. Budget and service life? High-volume, cost-driven builds favor the 1200; long-life, high-uptime plants favor the 1500.

More answers in the 1500 column than the 1200 column is your signal. If it is close, the 1200 or G2 usually wins on cost.

How to Buy Genuine S7-1200 / S7-1500 and Avoid Fakes

The Real Risk of Fakes and Grey-Market Units

You can pick the perfect CPU and still lose if the unit in the box is counterfeit or grey-market. Fakes and unauthorized imports show up as field failures, mismatched firmware, no valid warranty, and downtime that costs far more than the part. This is the layer buyers ask about most and find covered least.

How to Verify Authenticity

Use a simple checklist:

• Packaging and labels. Clean, correct Siemens packaging, intact labels, consistent printing, no signs of relabeling.
• 6ES7 order number match. Confirm the printed part number matches your ordered CPU and variant, character for character.
• Firmware. Verify the firmware version is a real Siemens release appropriate to the hardware.
• Seller credentials. Buy from a supplier who can show sourcing, stock, and a real warranty, not an anonymous listing.

What to Ask a Supplier

Before you commit, get clear answers on lead time, current stock, warranty terms, and global shipping. A serious supplier confirms the exact part number against your requirement rather than pushing whatever is on the shelf. That is what we do at CT Automation: confirm the genuine 6ES7 part, check live stock, and quote with warranty and worldwide delivery. Send us the order number you are considering and we will verify it and check availability.

FAQ

 

 

Is the S7-1500 just a newer version of the S7-1200?

No. They are different performance tiers in the same SIMATIC family, not old and new versions of one product. The 1200 is the compact controller for basic to mid-range machines; the 1500 is the high-performance controller for demanding, plant-scale, safety, and motion applications. Both are current.

Can an S7-1200 program run on an S7-1500, and the other way around?

Partially. Standard LAD and FBD logic and most technology objects migrate with some effort, but S7-Graph and STL do not port cleanly. Treat any cross-series move as a migration project with testing, not a copy and paste.

Can I mix S7-1200 and S7-1500 on the same PROFINET network?

Yes, and it is a common, deliberate design. A 1200 can run as an I-Device beneath a 1500 line controller, letting each machine keep its own program while the 1500 coordinates the line. Standardizing field I/O on ET200SP keeps the architecture clean.

Including software, how big is the real price gap?

Bigger than the CPU sticker suggests. The 1200 runs on low-cost STEP 7 Basic, while the 1500 requires the more expensive STEP 7 Professional. On small projects that license difference can exceed the hardware difference, which is why the 1200 often wins on total cost even when the CPUs look close.

Which exact CPU should I choose for my I/O count?

As a rough guide, small machines up to around 100 points map to a CPU 1214C or 1215C, while larger or performance-critical systems map to an S7-1500 with distributed I/O. Exact selection also depends on scan time, motion, and safety. Send us your I/O list, scan-time target, and axis count and we will map it to a specific CPU and order number.

How do I confirm I am buying genuine Siemens?

Check the packaging and labels, match the printed 6ES7 order number to your exact variant, verify the firmware is a valid Siemens release, and buy from a supplier who can show sourcing, stock, and a real warranty. We verify part numbers and stock before you order.

The Bottom Line

The right controller is the one that matches your needs, not the one that ranks higher on a spec sheet. For most compact, cost-driven machines that is the S7-1200 or its G2 generation. For high-speed, multi-axis, safety-rated, or plant-scale systems that is the S7-1500. For machines that live inside larger plants, running both together is often the smartest answer.

Once you know the series, the real question is the exact part and whether it is genuine. Send us your I/O points, scan-time target, and motion axis count, and we will come back with the specific CPU, the correct 6ES7 order number, verified genuine stock, and a quote.

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