Mitsubishi Electric vs Siemens PLC: The 5-Year Cost Error You Can't Afford

By John Doe, PE · Independent comparison · 2026

The penalty for choosing the wrong PLC platform over five years isn't a slightly higher line item—it's a cascading cost that compounds through replacement cycles, license lock-in, and lost production hours. Here, constraint propagation drives the analysis: each initial decision (hardware price, software ecosystem, spare parts availability) constrains the next, and the cumulative effect is a total cost that can differ by a factor of two or more. We'll test the myth that "a cheaper CPU always saves money" against the reality of the Mitsubishi Electric MELSEC iQ-F FX5U and the Siemens SIMATIC S7-1200.

Myth #1: "Lower hardware cost = lower TCO"

The claim: The Siemens S7-1200 CPU 1214C lists at roughly $350–$400 (depending on region), while the Mitsubishi FX5U-32MR/ES (32 I/O) is often ~$320–$370. A 10–15% hardware discount seems like a straight win for Mitsubishi PLC. Reality: That gap is real at the register, but it's a trap if you stop there. The FX5U's basic instruction time is ~34 ns vs the S7-1200's 85 ns (standard) / 40 ns (G2). That means for a 10,000-step control loop (common in packaging or sorting), the Mitsubishi finishes in ~340 µs; the Siemens PLC takes 850 µs. For a machine that runs 200 cycles per hour, that extra 0.5 ms per cycle is irrelevant—but for a high-speed pick-and-place or a cam-driven line, the slower scan can force you to either (a) oversize the Siemens CPU to a 1500 series or (b) accept lower throughput. Worked consequence: If the application requires a cycle time under 2 ms (e.g., servo interpolation at 1 kHz), the S7-1200 may not meet it, forcing an upgrade to S7-1500 (~$1,200 CPU). Suddenly the "cheaper" Siemens path costs $800 more in hardware alone. When it reverses: For slow processes—conveyor on/off, batch mixing, HVAC—the 85 ns vs 34 ns difference is noise. The cheaper Siemens buys you TIA Portal familiarity if your team is already Siemens-trained. The constraint propagates: if your plant is Siemens-only, the software reuse and spare part commonality may outweigh the CPU cost.

Myth #2: "Free programming software = lower total cost"

The claim: TIA Portal Basic (for S7-1200) is ~$300–$600 for a floating license, while GX Works3 for Mitsubishi is also ~$400–$600. "Both cost about the same." Reality: The constraint propagates through ecosystem. TIA Portal is a single-platform suite for Siemens from S7-1200 up to S7-1500 and drives; GX Works3 covers only Mitsubishi PLCs (and some legacy FX). If your control architecture includes 3+ different PLC families, TIA Portal's unified environment reduces training and integration costs. But for a purely Mitsubishi shop, GX Works3 is already the standard. Worked consequence: A plant that mixes Mitsubishi FX5U for simple stations and a Siemens S7-1500 for a high-speed line must license TIA Portal (another $1,000–$2,000) and GX Works3 separately—plus train electricians on two IDEs. Over five years with three engineers, that training overhead could reach $12,000–$18,000 (illustrative). When it reverses: If your facility is committed to a single vendor (all Mitsubishi or all Siemens), the software cost is a one-time hit that amortizes to ~$100/year per engineer. The myth that "free software" doesn't exist—both have costs—but the reality is that mixing platforms propagates a hidden training tax.

Myth #3: "Built-in I/O counts = expansion cost is equal"

The claim: Both the FX5U and S7-1200 offer 14 DI / 10 DO on-board and expand with modules. Reality: The FX5U can reach up to 512 I/O via CC-Link; the S7-1200 maxes out at roughly 128 digital I/O via signal modules and communication modules. For a machine that needs 200 I/O (e.g., a multi-station assembly line), the Mitsubishi can do it with one CPU and a few CC-Link remote stations ($150–$200 per I/O block). The Siemens would require a second CPU (S7-1200 with reduced headroom) or an upgrade to S7-1500 (~$1,200 CPU + separate I/O rack). Worked consequence: A 200-point system on Mitsubishi: one FX5U (~$350) + 3 CC-Link slave units (~$600 total) = ~$950. On Siemens: one S7-1200 (~$350) + 4 SM modules (~$500) + a second S7-1200 ($350) + PROFINET coupler ($300) = ~$1,500. The difference of $550 is real, but more importantly the two-CPU configuration adds programming complexity and potential inter-CPU communication latency. When it reverses: For small machines under 50 I/O, the built-in I/O on both is sufficient, and the expansion cost is negligible. The constraint propagates only when you cross the 128-I/O threshold—if you never do, the myth holds.

Decision Tree: Which PLC for Your 5-Year Cost?

Rule-based conclusion: If all four conditions tip toward Mitsubishi (fast cycle, single-vendor Mitsubishi, high I/O, no Siemens contract), the five-year total cost for Mitsubishi is roughly $1,200–$1,800 (CPU + software + spare), while Siemens would be $2,500–$4,500 (including possible upgrade, extra licenses, and downtime risk). If any condition reverses (slow process, Siemens house, low I/O, good contract), the Siemens path can be equal or cheaper. The myth that "hardware price determines TCO" is false; the constraints propagate and the real decision is your plant's specific operational envelope.

Topology/standards per the cited standards; all product ratings are manufacturer-stated values from the cited datasheets, current to 2026-06; derived/illustrative figures are labelled as such. This is not an independent head-to-head test. Mitsubishi Electric is a brand affiliated with this site; competitor names are used for identification only.