Rethinking IT Modernisation: Why SAP Projects Favour the Existing Core — and Why That Alone Is Not Enough

SAP is ending mainstream support for the widely used ECC system at the end of 2027. For mid-sized companies running SAP installations, that means one thing: decide, prepare and migrate — in under two years. Those who remain on ECC beyond that deadline face surcharges for extended maintenance or operate without security updates.

What surprises many: most companies are not opting for a clean-slate restart. They are converting their existing systems — an approach known as a Brownfield migration. There is more behind this choice than inertia. And yet, according to industry analyses, roughly 60 per cent of these projects still miss their budget, timeline or quality targets.

Brownfield, Greenfield, SDT — what the terms actually mean

Three migration approaches have become established in practice. Brownfield (system conversion) carries existing processes, configurations and data across to S/4HANA — faster, more cost-effective and with familiar workflows intact. Greenfield (new implementation) starts from scratch following SAP Best Practices — more modern, but significantly more effort. SDT (Selective Data Transition) combines both: certain areas are modernised while proven parts are carried over. For companies with functioning ECC processes and a tight timeline, Brownfield is the natural choice: research on S/4HANA migration shows that system conversions typically take six to twelve months — considerably shorter than Greenfield projects. The approach also preserves the operational knowledge built into processes and configurations over many years.

Why six in ten projects still miss their budget

Choosing the right migration path is only the first step. The most common causes of budget overruns are not the technology itself — but factors that can be identified and addressed in advance.

• Underestimated process change effort: Nearly half of companies cite business process adjustments as their biggest migration obstacle. Many treat the transition as an IT project — yet it requires business department ownership and decision-making authority at management level.
• Decades of custom development: A company that has run ECC for 15 years typically carries hundreds of Z-transactions and proprietary interfaces. These persist after a Brownfield conversion — they must be assessed, adapted or replaced.
• Resource scarcity: Qualified SAP consultants are in short supply, and day rates continue to rise as the 2027 deadline approaches. Companies that start their partner search too late will pay more and have fewer options.
• Missing change management: Few companies invest systematically in training and process workshops. Yet adoption at department level determines whether the new system actually gets used after go-live.

What mid-sized companies should do now

Companies that start now still have time for structured preparation. But Brownfield versus Greenfield is the wrong opening question. The first step is an honest stocktake — and sometimes the question of whether S/4HANA is the right destination at all. A solid IT advisory and technology assessment pays off far more before the first SAP consultant meeting than after.

• Create a customisation inventory: Which Z-code, proprietary interfaces and custom reports are running in production today? Without this overview, effort estimates are unreliable.
• Evaluate processes before systems: Which workflows function well, and which have been a workaround for years? Migration is a rare opportunity to shed legacy debt — but only if you know what it is.
• Get an independent assessment: SAP has an interest in customers moving to S/4HANA. Whether that is the right path for your business — or whether tailored software solutions for specific processes would be a better fit — is best answered by a neutral technology review. Our guide to custom software versus off-the-shelf solutions offers a starting point.
• Budget for change management from the start: Technical migration and accompanying measures should be budgeted roughly 60/40 — in practice the ratio is often 90/10, and that is where projects fail.
• Secure external capacity early: Qualified resources will become scarcer towards 2027. Delaying the partner search to 2026 means higher day rates and fewer options.

SAP migration is not an IT project — it is a business transformation that uses an IT tool. Those who only realise this after kick-off lose time and budget.

Plan IT modernisation strategically — first conversation with NoviCogi

This article was created with AI assistance and editorially reviewed.