Siemens vs Allen-Bradley: Which PLC Brand Should You Choose?
The two giants of industrial automation — Siemens and Rockwell's Allen-Bradley — together hold roughly 50% of the global PLC market. They dominate different regions, different industries, and different mental models. Here's the engineering comparison without the marketing.
In one paragraph
Pick Siemens for European plants, process industries, large OEMs, and integrated motion+safety+HMI projects where TIA Portal's breadth pays off. Pick Allen-Bradley for North American discrete manufacturing, machine builders, and any plant where the existing infrastructure is Rockwell. Don't pick on technical merit alone — pick on what your team, your customer, and your spare parts supply chain already speak.
Capability profile
Six-axis comparison. "Cost" is inverted (higher score = lower TCO).
Siemens
Allen-Bradley
Side-by-side comparison
| Aspect | Siemens | Allen-Bradley |
|---|---|---|
| Global market share | ~30% (#1 globally) | ~22% (#2 globally) |
| Regional dominance | Europe, Asia, Middle East, Latin America | North America, parts of Australia |
| Flagship platforms | S7-1200, S7-1500, S7-1500F (safety) | CompactLogix 5380, ControlLogix 5580, GuardLogix 5580 |
| Programming software | TIA Portal V19+ ($2,500-$15,000) | Studio 5000 Logix Designer ($5,500-$15,000+) |
| Default protocol | PROFINET (Ethernet) + PROFIBUS legacy | EtherNet/IP + DeviceNet/ControlNet legacy |
| Memory model | Address-based (DB blocks, M, I, Q, T, C areas) | Tag-based (named tags only, no fixed addresses) |
| IEC 61131-3 languages | LD, FBD, SCL (ST), GRAPH (SFC), STL (legacy IL) | LD, FBD, ST, SFC (no IL) |
| Best for | Process industries, automotive, packaging at scale, integrated motion | Discrete manufacturing, machine builders, automotive North America, food & beverage |
| HMI integration | WinCC Comfort/Advanced/Unified — all in TIA Portal | FactoryTalk View ME (panels) / SE (PC) — separate licenses |
| Safety integration | S7-1500F + TIA Portal Safety Advanced (SIL 3) | GuardLogix 5580 + Studio 5000 Safety (SIL 3) |
| Backward compatibility | Mixed — multiple architecture transitions | Excellent — ControlLogix unchanged since 1999 |
| Online editing | Strong — most changes don't require full download | Good but more changes require offline + download |
| North American support | Adequate (growing distributor network) | Excellent (dense distributor + integrator network) |
| European support | Excellent (home market) | Adequate but second tier |
| Job market in N. America | Growing (automotive, food, water utilities) | Dominant — vast majority of plant-floor controls roles |
| Job market in Europe | Dominant (especially Germany, Italy, France) | Available but less common |
Where each one wins
Siemens wins for
- • European plants and supply chains — home market, dense distributor network, German automotive standardisation
- • Process industries — refineries, chemicals, pharma, water treatment with deep PCS 7 integration
- • Integrated motion + drives + safety — TIA Portal handles all in one project
- • Online editing-heavy projects — most changes don't require full PLC download
- • Cost-sensitive plants under 20k I/O — Siemens hardware typically 15-25% cheaper than Rockwell equivalents
- • Plants standardised on PROFINET — native protocol
- • Large OEMs exporting to Europe and Asia — buyers expect Siemens
Allen-Bradley wins for
- • North American plants — dominant ecosystem, dense integrator network, plant electricians know Studio 5000
- • Machine builders — fast development cycles, AOI reuse, Studio 5000's clean tag system
- • Brownfield retrofits — old ControlLogix and even SLC-500/PLC-5 code migrates well
- • FactoryTalk-integrated plants — tight HMI/SCADA/MES coupling
- • Food & beverage, automotive in N. America — industry default
- • Plants standardised on EtherNet/IP — native protocol
- • Long-lifecycle assets — 20+ year backward compatibility on ControlLogix
Decision matrix: pick by your situation
| Your situation | Pick | Why |
|---|---|---|
| North American food & beverage plant | Allen-Bradley | Industry default; integrators all speak Rockwell |
| European automotive plant | Siemens | VW/BMW/Mercedes standardise Siemens; ecosystem aligned |
| Greenfield refinery / chemical plant | Siemens (PCS 7) | Integrated process control suite; SIL safety mature |
| Machine builder OEM exporting globally | Either — match customer | Customer's plant determines; both viable as branded options |
| Brownfield with existing ControlLogix | Allen-Bradley | Backward compat & spare-parts continuity |
| Brownfield with existing S7-300/400 | Siemens (S7-1500) | STL block migration path; team skills already aligned |
| Water utility, multi-site SCADA | Either — match SCADA | SCADA platform choice often drives PLC selection |
| Pharma / regulated batch facility | Siemens (PCS 7) common | 21 CFR Part 11 batch templates mature |
| High-speed packaging line | Allen-Bradley CompactLogix | Studio 5000 motion + Kinetix drives integration |
| Career change to controls — North America | Learn AB first | Most NA jobs require Studio 5000 fluency |
| Career change to controls — Europe/Asia | Learn Siemens first | Most EU/Asia jobs require TIA Portal fluency |
Programming experience compared
Tag naming — Allen-Bradley
(* Studio 5000 — pure tag-based memory *)
Pump1_Run := Start_PB AND NOT EStop_Pressed AND NOT Pump1_OL;
Conveyor1.Speed := Recipe.ConvSpeed;
IF Tank1.Level > Setpoint.HighLimit THEN Alarm.Tank1HiHi := TRUE; END_IF;Tag addressing — Siemens
(* TIA Portal SCL — DB-based memory addressing *)
"DB_Pump1".Run := "I_Inputs".StartPB AND NOT "I_Inputs".EStop AND NOT "DB_Pump1".OL;
"DB_Conv1".Speed := "DB_Recipe".ConvSpeed;
IF "DB_Tank1".Level > "DB_Setpoint".HighLimit THEN
"DB_Alarm".Tank1HiHi := TRUE;
END_IF;The functional logic is identical — what differs is the syntax and the memory model. Allen-Bradley tags exist as named entities in a flat namespace; Siemens tags live inside Data Blocks (DBs) with explicit qualified names. Both work; tag-based memory is generally easier for newcomers.
Cost comparison (typical 1,000 I/O system)
| Item | Siemens S7-1500 | Allen-Bradley ControlLogix 5580 |
|---|---|---|
| CPU + power supply | $3,500-$8,000 | $5,500-$12,000 |
| I/O modules (10x 32-pt) | $8,000-$12,000 | $12,000-$18,000 |
| Programming software | $2,500 (Basic) to $15,000 (Pro) | $5,500 (Std) to $15,000 (Pro) |
| HMI software (50 tags) | $1,500 (WinCC Comfort) | $3,500 (FT View ME) |
| Network switches | $1,500 (Scalance) | $2,000 (Stratix) |
| Hardware total | $17,000-$39,000 | $28,500-$50,500 |
| Cost premium | Baseline | +30-50% in N. America |
North American pricing shown. In Europe and Asia, Allen-Bradley premium can reach 50-80% above Siemens; in some Asian markets Mitsubishi displaces both at lower prices still.
The honest senior-engineer answer
When experienced controls engineers are asked "Siemens or Allen-Bradley?" the honest answer is almost always: match the existing ecosystem. If your customer's plant is 90% Rockwell, deliver Rockwell. If their plant is 90% Siemens, deliver Siemens. Mixed-vendor plants exist but cost the customer more in spare parts, training and integration headaches.
When you genuinely have a free choice (greenfield, no constraints):
- North American plant → Allen-Bradley by default. Local support and hiring pool dominate.
- European or Asian plant → Siemens by default. Same logic, opposite continent.
- Process plant anywhere → Siemens (PCS 7) or AVEVA-led architecture; Rockwell PlantPAx if Rockwell ecosystem is locked in.
- Heterogeneous multi-vendor → CODESYS-based platform (Beckhoff, Wago, others) or Ignition SCADA above multiple PLC brands.
Both are excellent. Both have produced reliable plants for decades. Don't agonise over the choice — match the ecosystem, deliver the project, move on.