There is no single "best" Siemens PLC. The right choice depends on your application size, I/O requirements, network topology, and—let's be honest—your budget. After tracking over $180,000 in PLC and control panel spending across 6 years, I've learned that what looks cheap on the quote often isn't once you factor in engineering time, spare parts, and downtime risk.
Below I break down four common scenarios. If you're struggling with which Siemens PLC to spec, how to read an S7-1200 datasheet, what a control panel cover should cost, or even how to check a backup battery without a multimeter (surprisingly common in the field), read on.
Small projects—lighting control, small conveyor, standalone machine—often pit the Siemens LOGO! against the entry-level S7-1200. The LOGO! price (as of January 2025) is roughly $120–$180 for the basic unit, whereas a bare S7-1200 (CPU 1211C) starts around $200. The LOGO! seems cheaper, but watch out for hidden costs.
From the outside, it looks like LOGO! saves you $50–$80 upfront. The reality: LOGO! has limited expansion (max 8 modules), no integrated PROFINET on older models, and the programming software (LOGO! Soft Comfort) is an extra ~$300 if you don't already own it. Meanwhile, TIA Portal Basic is free for the S7-1200 up to a certain project size. Over a 3-year lifecycle, I found the S7-1200 actually costs less when you include engineering software and future expansion.
My rule of thumb: If your project has fewer than 20 I/O and no need for Ethernet/IP or PROFINET, LOGO! is fine—but only if you already have the programming software. Otherwise, go S7-1200. (I learned that after buying a LOGO! starter kit and then spending $300 on software—ugh.)
Siemens publishes a detailed S7-1200 PLC datasheet online, but it's easy to get lost in specifications. As a cost controller, I focus on three lines:
Take this with a grain of salt: the price differences among models are small relative to the risk of under-specifying. I always buy one tier higher than my initial estimate—it saved me on three projects (and I'm not 100% sure it's always necessary, but the peace of mind is worth it).
Once you've picked the PLC, the electric control panel and its control panel cover become significant line items. People assume the panel is just a box—but the costs add up fast. A typical 600x400mm enclosure with cover, without cutouts, runs $80–$150 from a standard vendor. But if you need custom cutouts (mounting holes, cooling vents, cable glands), fabrication adds 40%–60%.
The most frustrating part of control panel procurement: hidden charges for cable gland plates, door-mounted disconnects, and temperature management. After our third project in Q2 2024, I started requiring suppliers to quote a full BOM including:
Pro tip: A standard control panel cover (no window) is cheaper than one with a viewing window. If you don't need to see indicators 24/7, skip the window—saves about $50 on average. (Not that I'm stingy, but $50 repeated across 20 panels adds up.)
I have mixed feelings about assembled control panels vs. building them in-house. On one hand, assembled panels save engineering labor ($120–$150/hour). On the other, they carry a markup of 25%–35% on components. My compromise: order the enclosure and basic wiring pre-assembled, but do the PLC integration ourselves. That reduced our delivery time by 2 weeks and cut the external premium in half.
This gets into a maintenance topic that isn't my primary expertise (I'm a procurement guy, not a service technician). But after years of coordinating with maintenance teams, I've picked up a few tricks. One common headache: verifying the backup battery health in a control panel or PLC UPS without carrying a multimeter.
I'm not 100% sure, but the method that several techs have shown me is a simple load test: Turn off the main power, measure the voltage drop rate by watching the PLC status LED dim. If the LED flickers out within 5 seconds, the battery is likely weak. This is similar to checking a car battery health without a multimeter—you observe how quickly the interior lights dim when you crank the engine. Of course, this is a rough proxy; for critical systems, always use a proper meter. But in a pinch, it works.
If you're wondering "how to check car battery health without multimeter" in the field, the same principle applies: turn on the headlights, then try to start the engine. If the headlights dim dramatically, the battery is struggling. For control panel batteries, a simple load test with a known resistor (like a 12V lamp) can also give you a quick health check. Not as accurate as a multimeter, but better than guessing.
Remember: the cheapest initial quote is rarely the cheapest total cost of ownership. When I compared 8 vendors over 3 months using my TCO spreadsheet, the vendor with the lowest PLC price actually cost us $1,200 more in hidden fees (expedited shipping, missing cable glands, etc.). Don't fall for it.
Pricing data referenced in this article is based on Siemens' online configurator as of January 2025. Verify current SIEMENS PLC price and S7-1200 datasheets at siemens.com/industrial-automation, as product details may have changed.