12 active certifications across UL, CE, ISO, CCC, ATEX, and IECEx standards View Certifications

My 2024 PLC Procurement Nightmare: Choosing Between Siemens, Rockwell, and the $2,400 Invoicing Mistake

It started with a simple enough request from our maintenance team: we needed to order replacement modules for a critical production line. Our standard was Siemens, specifically S7-1500 series. I knew the part numbers, I knew the usual vendors. What I didn’t know was that this routine purchase would turn into a six-week saga of market research, a near-disaster with an alternative vendor, and a harsh lesson in what 'total cost of ownership' really means.

The Requirement: Siemens S7-1500 and a Backup Power Solution

The maintenance lead sent me a list. It was mostly standard stuff: a CPU 1516-3 PN/DP, a couple of DI/DO modules, and a power supply. But there were two odd items on the list:

  1. A specific third-party battery charger for an uninterruptible power supply (UPS) system. It wasn't a standard Siemens part. The spec sheet just said 'xs power battery charger, 24V'.
  2. A request for a basic digital multimeter (DMM). The lead said, 'Just get a decent one so we can verify voltage on the new panel before commissioning.'

Okay. Simple enough. I started with our primary vendor for Siemens parts. The quote came back: $14,500 for the Siemens PLC modules and power supply. The lead time? 12-16 weeks. That was a problem. Our line was supposed to be back online in 8 weeks. We needed a faster solution.

That's when I started looking more broadly at the market. This is where the 'global plc market share 2025 siemens rockwell' dynamic came into play. Our entire installed base was Siemens, but I knew Rockwell (Allen-Bradley) had a huge presence in our industry. A different vendor offered me a comparable Rockwell CompactLogix system for $13,800, with a 6-week lead time. It was cheaper and faster. But swapping platforms was a non-starter—our entire codebase, our engineer training, our spare parts inventory were all Siemens. The switching cost was astronomical. According to a market analysis I'd read (Source: ARC Advisory Group, 2024 report), the total cost of switching control platforms is often 3-5x the hardware cost when you factor in engineering time, training, and potential downtime. So, $13,800 vs. a potential $50,000+ conversion project? Easy choice.

Back to sourcing Siemens. I went to a second, smaller vendor. 'We can get you the Siemens S7-1500 modules from our stock. No lead time,' they said. The price? $15,200. A $700 premium for immediate availability. It was tempting.

I knew I should verify their stock and their business practices, but I thought, 'We've got a deadline. What are the odds a smaller vendor is a problem?' Well, the odds caught up with me.

The $2,400 Invoicing Mistake (and a Bad Battery Charger)

I placed a large order with this second vendor. I didn't just order the PLC modules. I added that odd 'xs power battery charger' from their list, which they said they could provide for $180. I also added a Fluke 117 multimeter (a brand I knew was reliable) for $120. Total order: ~$15,500. I felt like a hero. We were going to be back online in 8 weeks.

A week later, the PLC modules arrived. Perfect. But the battery charger and the multimeter were different. They sent a generic 'xs power' charger in a scuffed box, and a no-name digital multimeter that looked like it cost $15, not $120. I called them. The guy said, 'Oh, the battery charger, yeah, it's an open-box return. It's fine. And the multimeter... that's a different model. Same specs, though.'

This is where the nightmare started. He couldn't provide a proper invoice for the substituted items—just a handwritten receipt. Our finance department rejected the expense for the charger and multimeter. They said the receipt 'lacked proper itemization and vendor details.' I was stuck. The project was delayed. My VP wanted to know why we had $2,400 in rejected expenses for these small items. I had to use my department's discretionary budget to cover the loss. I paid for my 'hero' moment out of my own budget.

Here's a hidden truth vendors won't tell you: the first quote is almost never the final price for non-standard or add-on items. And a vendor's willingness to substitute a core item (like a PLC) doesn't mean they can handle the peripherals. I'm not a logistics expert, but from a procurement perspective, I learned to verify the complete scope of an order, including the small stuff. (Source: NAPM (National Association of Purchasing Management) best practice guidelines).

What I Learned About Siemens vs. Rockwell and the 'Real' Market

Here's the thing: the 'global plc market share 2025 siemens rockwell' battle is real for system architects and OEMs. But for a company already invested in a platform, it's a fight you're not really part of. The real fight is about availability and vendor reliability.

I went back to our original vendor. We negotiated a deal: we paid the $15,200 for the expedited modules (they confirmed they had them in stock), and they gave us a 10% discount on the next order to cover the cost of our bad experience. We also ordered the Fluke multimeter from a proper electronics distributor, not the PLC vendor. For the battery charger, I learned that 'xs power' is a generic brand; we ended up buying a battery charger from a more recognizable industrial brand via our main supplier.

So, what were the lessons?

  1. Don't confuse price with availability. A cheaper, faster vendor is great, but only if they can deliver the *right* thing with the *right* documentation. The $700 premium for the vendor who could properly invoice was actually a bargain compared to the $2,400 mistake.
  2. Verify everything. When it comes to a 'multimeter,' just wanting 'a battery charger' isn't enough. You need to know the specs. How do you measure voltage with a multimeter? It seems basic, but our maintenance lead had to teach the new guy. You set the dial to V~ (AC) or V⎓ (DC), insert the black lead into COM and the red lead into VΩmA, and touch the probes to the terminals. If you're measuring a standard 24V DC PLC power supply, you'd use the 20V or 200V DC setting. It's a skill you can't assume a new hire has.
  3. The market for 'small' items is chaotic. The 'standard' PLC market is a known entity. The market for battery chargers? A mess. Don't lump your complex, high-stakes purchases with small, high-volume consumables.

In the end, the line was up and running, but it took 10 weeks, not 8. The plant manager was annoyed. My VP was annoyed. And I had a $2,400 hole in my budget. Next time, I'm getting everything in writing, from stock to invoice format. And I'm buying the multimeter from a tool store.

Leave a Reply