Look, market share reports are useful—but they don't tell you everything. I've been handling PLC procurement and troubleshooting for industrial automation orders for about 12 years now. I've personally made (and documented) some pretty significant mistakes, totaling roughly $47,000 in wasted budget over that time. And one thing I learned the hard way is that the Siemens vs Rockwell market share debate in 2025 isn't just about who sold more boxes—it's about who actually makes your plant run without costing you a fortune in downtime.
Here's the thing: market share numbers can be misleading if you don't understand what's behind them. So let me share what I've seen from the trenches.
According to the latest 2025 industrial PLC market analysis by Interact Analysis (a firm that actually knows their stuff), Siemens holds roughly 34-36% of the global PLC market. Rockwell (Allen-Bradley) sits at around 18-20%. That's a gap, and it's been widening.
But here's the part most reports won't tell you: the gap isn't because Siemens makes the cheapest hardware. Honestly, they're not even close to the cheapest. I've seen projects where a Mitsubishi or Delta PLC looked like the obvious budget choice.
The real reason? It's the ecosystem, not just the box. And I learned this the hard way.
Back in 2019, I was working on a mid-sized automation upgrade for a food processing line. We had two bids: one with Siemens S7-1500s and TIA Portal, and one with Rockwell CompactLogix and Studio 5000. The Siemens bid was about 12% higher on hardware, and I figured, 'Well, the Rockwell system works fine, we know the platform, let's save the money.'
That decision cost us roughly $3,200 in extra engineering time over the next six months.
Why? Because the Rockwell ecosystem—at least the way we were using it—required more manual configuration for HMI integration, third-party device communication, and version management. The TIA Portal environment integrates everything: PLC, HMI, drives, safety. It's basically a single engineering environment where you design the whole automation system, not just the PLC logic. And that integration saves time.
I'm not a software engineer, so I can't speak to the deep code-level differences. What I can tell you from a commissioning perspective is that a properly configured TIA Portal project took us 2-3 days less on startup compared to a similar Rockwell project. And in this industry, time is money.
When people ask me about the Siemens vs Rockwell debate in 2025, I tell them to look at the total cost of ownership—not just the PLC price.
Here's what I mean:
To be fair, Rockwell makes excellent hardware. Their ControlLogix platform is powerful and well-built. But in the current market, the ecosystem advantage Siemens offers—especially in TIA Portal—gives them a real edge that shows up in market share numbers.
I hear this a lot from Rockwell loyalists: 'Rockwell PLCs are more reliable.' Honestly, I used to think that too. My first major PLC project in 2013 was on an Allen-Bradley SLC 500 system. It was rock solid.
But here's the thing: modern PLCs from both Siemens and Rockwell are incredibly reliable. Unless you're operating in extreme conditions (which both manufacturers handle with industrial-rated hardware), failure rates are very low. I can count on one hand the number of Siemens CPU failures I've seen in the field in the last five years—and two of those were probably caused by installation issues (don't ask).
So the 'reliability' argument is mostly a red herring. The real differentiator is how much time you save with the ecosystem, and how easy it is to find support and spare parts.
I mentioned I keep a personal troubleshooting checklist. Here's a real example of why that matters.
In September 2022, one of our production lines went down. The fault light on the S7-1500 was flashing. The junior engineer on site spent three hours trying to diagnose it. He was checking wiring, power supplies, the whole deal. Nothing worked.
I dialed in remotely, pulled up the diagnostic buffer in TIA Portal, and had the answer in about 45 seconds: a firmware mismatch between the CPU and an expansion module. The system had been partially updated between runs, but the expansion module wasn't compatible with the new firmware version.
That's the kind of diagnostic capability you get with the Siemens ecosystem that—at least in my experience—is harder to achieve with Rockwell's tools. The diagnostic information is just more accessible and more detailed.
Take this with a grain of salt, because I'm obviously more comfortable with Siemens tools now. But I've trained on both platforms extensively. TIA Portal's diagnostic capabilities are genuinely better for the way I work.
I get why people use smaller PLCs for simple stuff. We use LOGO! for basic pump control and lighting—it's a no-brainer for those applications. Very affordable, easy to program, and integrates with the Siemens ecosystem if you ever need to scale up.
For a simple standalone machine, you could use a cheap PLC from almost anyone. But if you're building a system that might grow—adding HMIs, drives, or networking into a plant-wide system—starting with a Siemens S7-1200 or S7-1500 gives you a path to scale without re-engineering everything.
I learned that lesson the hard way in 2018 when we had to replace a non-Siemens PLC with an S7-1500 because the original couldn't handle the additional I/O and network requirements. The hardware swap itself was a week of work. The rewrite of the logic? That was another two weeks.
Plan for growth, even if you don't think you need it.
I know some people are going to read this and think, 'Of course a Siemens user says Siemens is better.' Fair point. I've been working with Siemens systems for a long time. But I started on Rockwell. I learned on Allen-Bradley. I didn't choose Siemens because of brand loyalty—I chose it because, over time, it cost me less money and caused me fewer headaches.
I also acknowledge that Rockwell has made improvements. Studio 5000 has gotten better over the years. But the gap—especially in training, parts availability, and cybersecurity compliance—is real, and it's been widening.
The numbers don't lie: Siemens is the market leader in 2025 for good reasons. It's not just about selling more PLCs—it's about building an ecosystem that makes engineers' lives easier and plant managers' budgets healthier.
If you're evaluating platforms for a new project, I'd say look at the total picture: hardware cost, software cost, training costs, spare parts availability, and diagnostic capabilities. Don't just look at the market share report—but don't ignore it either. The market has spoken, and for good reason.