What We're Really Comparing Here
When I first started handling our company's electrical component orders — roughly $120,000 annually across maybe 15 vendors — I assumed Siemens PLCs and control panel switches were just different tiers of the same thing. Spoiler: they're not. And confusing the two can cost you more than just a headache with your engineering team.
In this piece, I'm comparing Siemens Simatic PLCs (specifically the S7-1200 and S7-1500 series) against industrial control panel switches — the physical buttons, switches, and pilot devices that operators actually push. They seem like they're in different categories, but when you're the person placing the orders and reconciling the invoices, you need to understand where they overlap and where they absolutely don't.
The way I see it, here's the core of the comparison:
- Function — Is the control panel switch just a dumb button, or does it do more?
- Integration — How easily do these parts work together in a real control cabinet?
- Cost — What's the total cost of ownership for a PLC versus a panel switch setup?
- Procurement — What an admin buyer should know before placing that PO.
I'll be upfront: I'm not an engineer. I'm the person who makes sure the engineers have what they need, on budget, on time, and with proper invoicing (note to self: still recovering from that $2,400 rejected expense from 2022).
Dimension 1: Function — Brains vs. Interfaces
This is the first place where the comparison gets interesting. Most buyers focus on what each part does and completely miss what each part requires.
The PLC Perspective
A Siemens Simatic PLC — whether it's the S7-1200 for compact applications or the S7-1500 for high-performance needs — is the brain of the operation. It takes inputs, runs a program, and controls outputs. According to Siemens' own documentation, the S7-1200 supports up to 8 signal modules, meaning you can scale it pretty extensively for a mid-sized production line.
From a procurement standpoint, here's what that means: the PLC itself is just the start. You also need the power supply, the signal modules, maybe a communication processor, and definitely the TIA Portal software license. The sticker price on the PLC might look reasonable — say $400-$1,200 for a mid-range S7-1200 — but the total system cost adds up fast.
The Control Panel Switch Perspective
Control panel switches — like the ones used in a Pentair IntelliCenter indoor control panel — are much simpler. They're push buttons, selector switches, emergency stops. They don't run code. They don't have firmware updates (thankfully). They just make or break a circuit when someone pushes them.
But here's the catch: a control panel switch is useless without the PLC (or at least a relay) behind it. It's the interface. You need both to make a functional system. The switch tells the PLC what to do; the PLC decides and acts.
Early conclusion (and this surprised me): If you're a small operation looking at an automated system, both are mandatory. But the PLC is the cost and complexity driver. The switches are relatively cheap and easy to source. The question everyone should ask is not 'which is better?' but rather 'what's missing from my BOM?'
Dimension 2: Integration — How They Fit in a Control Cabinet
Integration is where theory meets reality. I'll be honest—when I first started ordering parts, I thought everything would just snap together like LEGO. It does not.
PLC Integration
Siemens PLCs from the S7 series use a standardized backplane and DIN rail mounting. The S7-1200, for example, snaps onto a 35mm DIN rail and the signal modules lock onto the PLC without additional wiring. That's the good news.
The less obvious challenge: you need the right power supply for your specific PLC model, and Siemens has a range of them. The S7-1200 typically uses a 24V DC power supply, but the current rating depends on how many modules you've added. I've made this mistake — ordered a 2.5A supply for a system that actual needed 4.5A. That cost us a $180 emergency order and a delayed project.
Also, if you're thinking about how to install an electrical outlet inside the control cabinet for the PLC power supply (yes, that's a real consideration), US wiring codes (per the National Electrical Code) have rules about what's allowed inside an industrial control panel. Short version: it's doable, but not always recommended for high-voltage circuits near control voltage.
Control Panel Switch Integration
Panel switches are mechanically simpler, but integration-wise they can be trickier than you'd think. A typical Pentair IntelliCenter indoor control panel, for instance, uses a combination of circuit breakers, relays, and pushbutton switches. The switches themselves mount into standard 22mm or 30mm panel cutouts.
The procurement challenge: not all switches are compatible with all controllers. A switch that works with an Allen-Bradley PanelView might not wire up cleanly to a Siemens Simatic HMI. And while the physical wiring might work (it's just connecting contacts), the functionality can be limited if the switch type (momentary vs. maintained, N.O. vs. N.C.) doesn't match the controller's program expectations.
What I learned after 3 years and about 150 orders: Always ask the engineering team for a wiring diagram reference before ordering. Not just a parts list. I've had orders that looked complete but were missing one specific type of selector switch contact block because 'it looked the same' from the picture. It wasn't.
Dimension 3: Total Cost of Ownership — Hidden Costs Are Real
I only believed in tracking total cost of ownership (TCO) after I ignored it and got burned. A vendor offered me 'matching' Siemens PLC parts at 30% less than our regular distributor. Sounded great. I ordered six S7-1200 series units. They arrived, but three had firmware versions that weren't compatible with our TIA Portal version. We paid $800 to get them updated at a third-party shop, plus two weeks of engineering rework (note to self: never again).
PLC TCO Breakdown
- Hardware: $400–$1,500 per PLC, plus $100–$300 per signal module
- Software: TIA Portal licenses range from $1,500 (basic) to $7,000+ (professional). This is a deal-breaker for small shops.
- Training: Siemens certified training is roughly $2,000–$3,000 per course per person. Not optional if you want people who know what they're doing.
- Support & maintenance: Expect 10–15% of hardware cost annually for firmware updates and spare parts (based on our 2024 vendor consolidation project).
Control Panel Switch TCO Breakdown
- Hardware: $5–$30 per switch, depending on type and illumination. A fully-illuminated E-stop might hit $50.
- Installation: Labor cost for panel cutout and wiring. Roughly $20–$40 per switch if done by a controls electrician (based on quotes we got in early 2025).
- Replacement: Individual switches fail maybe 1 in 10,000 cycles. Replacement cost is low unless it's a specialty part.
Bottom line: If you're budgeting for a project, allocate 70–80% of your controls budget to the PLC system (hardware + software + engineering). The switches and panel components are the remaining 20–30%. That's a rough ballpark from my experience managing about 60 orders per year for the last 4 years.
Dimension 4: Procurement — What an Admin Buyer Actually Needs to Know
Since I report to both operations and finance, I have to balance speed with accuracy. Here are three things I wish I'd known earlier:
1. Siemens PLCs Have Strict Compatibility Requirements
You can't mix S7-1200 modules with S7-1500 racks. I know, that sounds obvious. But I've seen vendors list 'S7 series compatible' parts that only work with specific firmware versions. A friend in procurement — from a 400-employee facility — told me he once accidentally ordered S7-300 series parts for an S7-1200 project. The engineering team politely told him where he could store them.
My advice: Before placing any Siemens PLC order, send the part numbers from the project BOM to the engineering lead for a quick verification. It takes 5 minutes and saves you from eating a cost (ask me how I know).
2. Control Panel Switches Are Not All the Same
I can't count how many times I've seen 'Pentair IntelliCenter compatible' switches that are NOT actually compatible because the contact blocks are different. The IntelliCenter indoor control panel uses a specific set of I/O modules — if you order a switch that requires a different contact voltage rating, it won't work.
To be fair, most switch manufacturers are good about listing compatibility. But always check the wiring diagram. I get why people assume 'a switch is a switch' — I thought the same. But the truth is, when you're integrating into a control system, the switch's electrical rating (voltage, current, DC vs. AC) matters.
3. How to Install an Electrical Outlet in a Control Panel — Yes, It's a Real Question
I've seen this question come up a lot in procurement discussions: how to install an electrical outlet inside a control panel. Here's the regulatory reality according to the National Electrical Code (NEC):
- You can install a 120V AC outlet inside an industrial control panel for servicing tools, but it must be on a dedicated circuit with GFCI protection (NEC 210.8(B)).
- The outlet must be listed for use in the environment (e.g., NEMA 4X for wet locations).
- Per NEC 409, the panel itself must have adequate space and clearances for additional wiring — you can't just stuff an outlet in there.
The short version: it's legal, but get a licensed electrician to do it. Trying to DIY this can void your panel's UL listing and — more importantly — lead to serious safety hazards. In one of our plants, a poorly mounted outlet shorted out and tripped the entire panel during a night shift. That shutdown cost us roughly $3,000 in lost production. (Source: internal maintenance log, Q2 2024.)
So, What Should You Buy?
If you're feeling overwhelmed by the choices, here's my take based on five years of managing these relationships:
- If you need automation: You need a Siemens PLC, no question. The S7-1200 is great for standalone machines or small processes. The S7-1500 handles multi-axis machines and larger distributed systems. Pair it with the right control panel switches for operator interfaces. Don't overthink this part.
- If you need control panels (like Pentair IntelliCenter indoor panels): Focus on the switch selection. Make sure the switches match the panel's I/O requirements. If you're retrofitting, get the original panel's wiring diagram.
- If you're a small company buying for the first time: Spend the money on the PLC and the training. The switches are cheap by comparison. An informed customer asks better questions and makes faster decisions. I'd rather spend 10 minutes explaining options than deal with mismatched expectations later.
I'm not 100% sure about future market trends, but my best guess is that Siemens will continue to dominate the PLC market for the foreseeable future. The ecosystem is just too entrenched. Prices as of early 2025 for an entry-level S7-1200 starter kit run about $450 (verify current pricing at a Siemens distributor or authorized partner). Control panel switches from brands like Pentair or Eaton are roughly $8–$35 each (based on quotes I reviewed in January 2025).
One more thing — and I really should do this myself more often: document your decisions. When you order a PLC, write down why you chose it. When a panel switch fails after 3 years, note it. Over time, you'll build a personal database of what works and what doesn't. That's gold.