Make or Buy: PLC Migration In-House vs. Service Provider

The decision between in-house PLC migration and hiring an external integrator depends on three factors: your team's S5/S7 expertise, the complexity of the system, and whether the system includes safety-critical functions. Simple machines with basic logic can be migrated in-house at 30–50% lower cost. Complex systems with safety functions, communication networks, and HMI integration are better handled by experienced integrators. This guide helps you make the right choice.

The Two Options#

Option A: In-House Migration#

Your own maintenance or automation team handles the entire migration: analysis, hardware selection, program conversion, testing, and commissioning.

When this works well:

• Your team has experience with both STEP 7 Classic and TIA Portal
• The S5 program is small to medium (under 100 blocks)
• The program uses standard logic (bit operations, timers, counters, basic arithmetic)
• No safety-related functions (no SIL/PL requirements)
• The machine is not production-critical (downtime for troubleshooting is acceptable)
• You have or plan multiple migrations (learning curve pays off)

Typical cost: €3,000–30,000 per machine (see migration cost guide)

• Hardware: same cost regardless of who does the work
• Software: same cost
• Engineering: €50–80/hour internal rate vs. €100–180/hour external
• Savings: 30–50% on engineering cost (the largest cost block)

The real cost of in-house: Your team's time is not free. While they are working on the migration, they are not doing their normal maintenance work. If your plant has only one or two automation technicians, tying them up for weeks on a migration project creates a maintenance backlog and increases the risk of unplanned downtime elsewhere.

Option B: External Integrator (System House / Solution Partner)#

A Siemens Solution Partner or specialized system integrator handles the migration project.

When this is the better choice:

• Your team has limited or no S5 experience
• The program is large (100+ blocks) or uses complex features (indirect addressing, communication blocks, analog processing)
• Safety-related functions are involved (SIL, PL, emergency stop circuits)
• The machine is production-critical (zero tolerance for extended downtime)
• A single migration (learning curve does not pay off)
• You need guaranteed results with contractual liability

Typical cost: €10,000–100,000+ per machine

• Engineering: €100–180/hour (Western Europe/US)
• Often quoted as fixed price for defined scope
• Includes documentation, testing, and commissioning
• May include warranty period for post-migration support

The real value of external: An experienced integrator has done dozens of S5→S7 migrations. They know every pitfall — the timer types that behave differently, the data block addressing trap (DW×2), the indirect addressing patterns that the converter cannot handle. What takes your team 3 weeks of troubleshooting, they solve in 3 days.

Decision Matrix#

The Hybrid Approach (Often the Best Answer)#

Many companies choose a middle path:

Phase 1: External integrator does the first migration as a reference project. Your team observes and learns. The integrator delivers a fully documented, tested, and commissioned system.

Phase 2: Your team does subsequent migrations using the first project as a template. The integrator is available for consulting on specific questions.

Phase 3: Your team handles all future migrations independently. The initial investment in external expertise pays off across many projects.

This approach combines the quality assurance of an experienced integrator with the long-term cost efficiency of in-house capability. The first machine costs more, but machines 2–10 cost significantly less.

What PLCcheck Pro Changes About This Decision#

Traditionally, the biggest argument for external integrators was S5 expertise. Understanding S5 AWL code, knowing the timer behavior differences, handling the DW×2 address conversion — this specialized knowledge justified the premium hourly rate.

PLCcheck Pro shifts this balance:

• Code analysis: Your team uploads the S5 code and gets an instant explanation — no S5 expertise needed
• Timer conversion: All KT values automatically identified and converted to IEC format
• Address mapping: DW→DBW conversion done automatically for all data blocks
• Documentation: Generated instantly, not after hours of manual analysis

This means your in-house team can handle migrations that previously required external expertise. The tool does not replace the need for TIA Portal knowledge or commissioning experience, but it eliminates the S5-specific knowledge barrier that was the main reason to hire externally.

The new math: Instead of paying €150/hour for an integrator's S5 expertise, your €60/hour in-house technician uses PLCcheck Pro (€199/month) to bridge the gap. For a single machine migration, the tool cost is less than 2 hours of external engineering time.

Try PLCcheck Pro →

Red Flags: When You MUST Use an External Expert#

Regardless of cost considerations, use an external expert when:

• Safety functions (SIL/PL) are involved. Incorrect migration of safety logic can cause injuries or death. Safety validation requires certified expertise.
• The program uses extensive indirect addressing (DO, LIR, TIR). This requires deep S5 architecture knowledge that tools cannot fully automate.
• Multi-CPU communication is involved. Systems where multiple PLCs exchange data via PROFIBUS, MPI, or Ethernet require careful migration of communication blocks.
• Regulatory compliance requires third-party validation. Some industries (pharma, food, nuclear) require independent verification of control system changes.

Frequently Asked Questions#

Can a maintenance electrician do a PLC migration?

If they have TIA Portal experience and understand PLC programming concepts, yes — for small, non-safety-critical systems. PLCcheck Pro can provide the S5-specific knowledge they lack. For complex or safety-critical systems, a PLC programmer or automation engineer is needed.

How do I find a good Siemens integrator?

Start with the Siemens Solution Partner finder (siemens.com/partner). Look for integrators who specifically list S5→S7 migration experience. Ask for references from completed migration projects. A good integrator will visit your plant, assess the system, and provide a fixed-price quote before starting work.

What if the integrator's quote is too expensive?

Get multiple quotes (at least 3). Compare scope carefully — some include documentation and training, others do not. Consider the hybrid approach: let the integrator do the complex parts (conversion, safety validation) while your team handles the simpler parts (hardware installation, wiring, I/O testing).

Should I ask for a fixed price or hourly rate?

Fixed price for clearly defined scope. Hourly rate for discovery/analysis phases where scope is uncertain. Never accept a pure hourly engagement for a full migration — there is no incentive for the integrator to finish quickly.

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Maintained by PLCcheck.ai. Last update: March 2026. Not affiliated with Siemens AG.