The cost of picking the wrong micro PLC isn’t the purchase order — it’s the 18‑month re‑engineering bill when you outgrow the platform. Below, we walk through a real‑world worked scenario: a packaging line originally quoted with a Mitsubishi iQ‑F FX5U vs. a Siemens S7‑1200 (CPU 1214C), and where the five‑year total cost actually lands.
Numbers: Mitsubishi FX5U basic instruction ~34 ns; Siemens S7‑1200 (1214C) ~85 ns (40 ns on G2). On paper, Mitsubishi is 2.5× faster.
Mechanism: That 34 ns figure is for a single LD instruction with no operand load. In a realistic 500‑step program with mixed math, data moves, and ethernet stack overhead, the gap narrows because the Siemens PROFINET stack runs tighter integration with the application cycle — the CPU doesn’t poll the network, it’s event‑driven via the TIA Portal runtime. The Mitsubishi FX5U, by contrast, uses a separate communication co‑processor that adds jitter on mixed I/O + motion cycles. The effective scan time in a mixed program is roughly 120 µs (Mitsubishi) vs. 160 µs (Siemens PLC) — a 33 % difference, not 150 %.
Worked consequence: On a pick‑and‑place cell with 3 servo axes (positioning via built‑in pulse trains) and 64 digital I/O, the Mitsubishi can sustain about 25 cycles/min; the Siemens does 22 cycles/min. That’s ~12 % lower throughput. Over five years (2‑shift, 240 days/yr, 22 cycles/min vs 25), the Siemens line delivers ~285,000 fewer cycles per year — roughly 4.2 % fewer parts. For a machine making 35 €/1000 parts, that’s ~4,000 €/yr lost.
Reversal: If your cycle time is governed by a mechanical cam (say 8 sec per part), both CPUs idle 90 % of the scan. That 33 % scan difference disappears. Mitsubishi’s speed advantage only converts to cash when the machine is cycle‑limited by the PLC scan. Below ~2 ms target cycle, the FX5U pulls ahead; above 5 ms, it’s irrelevant.
Numbers: Siemens uses TIA Portal (STEP 7 Basic for S7‑1200); Mitsubishi uses GX Works3. Both support IEC 61131‑3. Siemens average engineering time to program a 64‑I/O machine with one HMI: ~65 hours (experienced integrator) vs. Mitsubishi ~72 hours (same machine, same integrator) — based on a surveyed panel of 12 machine builders (illustrative).
Mechanism: TIA Portal unifies controller configuration, network topology, HMI screens, and drive parameters in one project tree. GX Works3 is separate software for the PLC; the HMI (GOT) uses GT Designer3, and CC‑Link configuration requires a third tool (GX Configurator). Each tool switch adds context‑reload time and increases the risk of addressing errors. The Siemens library concept (global libraries with versioning) also cuts reuse time by ~15 % on the second machine.
Worked consequence: Assume 7 hours saved per machine × your internal rate of 85 €/hr = 595 € saved per unit. Over a five‑year programme with 12 machines, that’s 7,140 € of engineering cost — more than the hardware cost of three S7‑1200 CPUs. And the first machine’s HMI tags don’t need re‑mapping on the Siemens side because the HMI is integrated in the same tag table.
Reversal: If your team already owns 50+ GX Works2/3 projects and GT Designer3 macros, the transition cost to TIA Portal exceeds the per‑machine savings. Mitsubishi’s ecosystem is highly efficient for shops that never mix HMI brands and never add third‑party drives. The trap is trying to mix a Mitsubishi PLC with a Siemens HMI or an off‑the‑shelf Modbus TCP sensor — that’s where GX Works3’s weaker third‑party integration becomes a time sink.
Numbers: Siemens S7‑1200 (1214C) on‑board: 14 DI / 10 DO / 2 AI; expandable via signal modules and boards. Mitsubishi FX5U on‑board: up to 96 I/O on CPU (512 with CC‑Link); integrated 2‑ch 12‑bit analog input + 1‑ch 12‑bit output.
Mechanism: The Mitsubishi FX5U packs more on‑board I/O and analog channels natively, which looks cheaper on a BOM. But the expansion bus is proprietary CC‑Link — adding a remote I/O node or a third‑party encoder requires a CC‑Link interface module and configuration in GX Configurator. Siemens uses PROFINET (open standard, IEC 61158); any PROFINET‑capable remote I/O (e.g., ET200SP, third‑party blocks) plugs in with automatic device identification in TIA Portal. Cost to add 16 digital inputs after installation: Siemens ~280 € (ET200SP, 1 module + bus adapter), Mitsubishi ~340 € (CC‑Link slave + terminal block + configuration time) — assuming no spare slot on the CPU rack.
Worked consequence: In year three, the packaging line needs 8 extra sensors (vibration, temperature) and a remote I/O station near a robot cell. Siemens retrofit: 2 hours engineering + 550 € hardware (ET200SP station + 2 modules). Mitsubishi retrofit: 5 hours engineering + 780 € hardware (CC‑Link slave + analog module + configuration software unlock). The five‑year difference for this one expansion: ~520 €. If the machine expands twice, the gap exceeds 1,000 €.
Reversal: If the original machine uses every on‑board I/O and never expands, the FX5U’s higher density costs less upfront. The break‑even is around the first retrofit event. For greenfield designs with fixed I/O counts, the Mitsubishi BOM wins; for machines that evolve, Siemens’ open‑network ecosystem pays back the initial premium.
Numbers: Siemens offers free TIA Portal basics training (SITRAIN digital) and a global spare parts network with 48‑hour delivery in EU. Mitsubishi FX5U spare PLC lead time from regional distributors: 5–12 days (EU, typical).
Mechanism: The Siemens S7‑1200 is one platform across the entire SIMATIC family — a technician who learns TIA Portal can program S7‑1500, ET200SP, and even safety controllers without re‑training. Mitsubishi’s FX5U uses GX Works3, but the larger MELSEC iQ‑R (high‑end) uses GX Works3 with a different hardware configuration paradigm. The learning curve for plant maintenance is steeper if you have mixed MELSEC families. Additionally, the S7‑1200 has a removable SIMATIC memory card that stores the entire project and firmware — a replacement CPU boots up in
Worked consequence: In a five‑year period, assume one CPU failure (3 % annual failure rate typical for industrial electronics). Siemens downtime cost: 4 h (detection + swap + boot) × 350 €/h = 1,400 €. Mitsubishi downtime: 7 h (detection + swap + download + re‑commissioning) × 350 €/h = 2,450 €. Difference: 1,050 €. Add one training day for a new technician (Siemens training cost 0 € online vs. Mitsubishi 1,200 € for GX Works3 course) and the support gap widens further.
Reversal: If the site already has three Mitsubishi MELSEC programmers and a stocked spare‑CPU cabinet (no delivery lead time), the training cost is sunk and the swap procedure is fast. The advantage only materialises for sites that standardise on one platform family. For pure Mitsubishi houses, the FX5U is cheaper to support because the installed base is homogeneous.
| Rank | Platform | Five‑year TCO (hardware + engineering + expansion + downtime) | Best for… |
|---|---|---|---|
| 1 | Siemens S7‑1200 (1214C) | ~€58,200 (€4,850/machine) | Mixed‑vendor plants, frequent retrofits, multi‑machine standardisation |
| 2 | Mitsubishi FX5U | ~€62,400 (€5,200/machine) | High‑speed low‑I/O machines, pure Mitsubishi shops, fixed I/O designs |
*Assumptions: 12 machines × 64 I/O; 1 CPU failure; 2 mid‑life expansions; labour rate 85 €/h. All figures approximate and scenario‑dependent.
Who should buy Siemens S7‑1200: Machine builders with multiple projects, any need for third‑party components, or a requirement for rapid CPU swap. Expect to save ~€350–€1,500 per machine over five years relative to Mitsubishi, primarily from easier expansion and integrated engineering.
Who should buy Mitsubishi FX5U: High‑volume, fixed‑I/O machines (e.g., simple conveyor palletisers) where every microsecond counts and the hardware list never changes. You’ll get a lower upfront BOM ($) and faster raw processing.
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. Siemens is a brand affiliated with this site; competitor names are used for identification only.