Not every old system needs a rewrite – Encapsulate often cheaper
Altlast analysis costs €3,000–2,000 and is mandatory
Data migration accounts for 15–30 % of the total budget
Parallel operation protects production – no Big Bang release
Replacing legacy software costs € 10,000 to €250,000 depending on the strategy. This article explains the four modernization strategies (Encapsulate, Rehost, Replatform, Rewrite), typical costs and why parallel operation of the Big Bang always strikes.
“Digitalization is not an IT project—it is a business strategy.”
– Björn Groenewold, Managing Director, Groenewold IT Solutions
Replacing Legacy Software: Costs, Risks, and a Step-by-Step Roadmap
What This Is About
Short: Short answer: Replacing legacy software typically costs between €10,000 and €250,000 depending on your modernization strategy.
Short answer: Replacing legacy software typically costs between €10,000 and €250,000 depending on your modernization strategy.
A Delphi system that has been running for 15 years is not broken – it is invisible. The entire business logic is in undocumented units. No developer wants to touch it.
Every change costs three times. This is Legacy software.
This article shows what modernization really costs, what strategy fits for what situation, and why the Big Bang is almost always a mistake.
Groenewold IT Solutions · Experiences from 250+ projects
Four strategies – not every old system needs a rewrite
Short: The most common mistake in legacy projects: a complete new building (rewrite), although a cheaper strategy leads to the same result.
The most common mistake in legacy projects: a complete new building (rewrite), although a cheaper strategy leads to the same result.
Strategy 1: Encapsulate (API capsule)
Short: The old system remains unchanged.
The old system remains unchanged. An API layer is built to connect modern applications (new web UI, mobile app, external partners). The old system is no longer visible.
**When: Core logic is stable, but the UI or interfaces are outdated.
Costs: 10,000–30,000 €
Risk: Low – old system is not touched
Strategy 2: Rehost
Short: The system relies on new hardware or cloud infrastructure.
The system relies on new hardware or cloud infrastructure. Software remains identical. Profit: lower operating costs, better availability, end of dependency on outdated hardware.
** Costs:** 5,000–25,000 €
Strategy 3: Replatform
Short: The system is upgraded to a new runtime environment: e.
The system is upgraded to a new runtime environment: e.g. from .NET Framework 4.8 to .NET 8, from PHP 5 to PHP 8, from Delphi 6 to Delphi 12.
The code is adjusted, but the architecture remains preserved.
Costs: 20.000–80.000 €
Strategy 4: Rewrite (targeted new development)
Short: Only where the old system is no longer structurally viable.
Only where the old system is no longer structurally viable. In practice, this is rarely the entire system, but individual modules.
Risk assessment of the four modernisation strategies
Strategy/th>
Risk
Duration/th>
Recommended if
tr style="background:#ffffff">
Encapsulate (API layer) <'td style="padding:10px 14px;font Not applicable Not applicable : > High/td>
Alt system no longer capable of carrying
Groenewold IT Solutions · Experiences from 250+ projects · Stand 2026
Short: In a Delphi system that was used for 15 years, there is often more business knowledge in the database than in the application itself.
In a Delphi system that was used for 15 years, there is often more business knowledge in the database than in the application itself. Calculation rules that are not documented elsewhere.
Special treatments for individual customers. Historical data that must be stored for GoBD.
Old system and new system run parallel, results are compared
∅ 150.000 €
Cutover & shutdown · 1–2 weeks/span>
Freeze window, Delta-Sync, Rollback plan, Altsystem shut off
Practice Example: Delphi 6 → .NET 8 (Production Control)
Short: For a manufacturer with 200+ machine connections, we migrated a 15 year old Delphi-6 production control into a .
For a manufacturer with 200+ machine connections, we migrated a 15 year old Delphi-6 production control into a .NET-8 web app.
| | | | |
|--|--|
| Parallel operation | 6 months (no production stop) |
| Migration duration total | 14 months |
| Project volume | about 95,000 € |
| Maintenance expenditure after migration | –70 % |
| Machine connections via OPC-UA | 200+ |
“A Delphi system running for 15 years is not broken – but it is invisible. The first phase is always archaeology." – Björn Groenewold, Dipl.-Inf.
Frequently asked questions
Can we continue working during migration?
Yes – that is even the normal case. Parallel operation (old system and new system running simultaneously) is the gold standard for critical productive systems.
Only when all tests are green, the old system is switched off.
What happens if the old system is only understood by one person?
We call this "knowledge risk' and is an independent part of the Altlast analysis.
We conduct structured interviews, document implicit knowledge and create a knowledge repository – before the person retires or leaves the company.
How long does a typical legacy project last?
Capsulation/Rehost: 4–10 weeks. Replatform: 3–8 months. Full rewrite: 9–24 months. With parallel operation at the upper limit, without at the lower.
What does it cost to do nothing?
This is a serious question. Unpatched systems are security risks. Outdated runtimes lose support. If the only developer who knows the system leaves the company, it can be existentially threatening.
We call this the 'Stylish Price' and calculate it explicitly in our recommendations.
*Groenewold IT Solutions, Empty – Legacy Modernization for the German mid-sized businesses since 2012. Request legacy system assessment. *
Technical sources and further links
Short: The following independent references complement the classification on the topics of this Article:
The following independent references complement the classification on the topics of this Article:
Managing Director of Groenewold IT Solutions GmbH and Hyperspace GmbH
Since 2009 Björn Groenewold has been developing software solutions for the mid-market. He is Managing Director of Groenewold IT Solutions GmbH (founded 2012) and Hyperspace GmbH. As founder of Groenewold IT Solutions he has successfully supported more than 250 projects – from legacy modernisation to AI integration.
Companies use funding for digitization in a targeted manner - with clear project logic, appropriate programs and less risk in application and implementation.
For topics like Legacymodernization we offer matching services – from app development and AI integration to legacy modernisation and maintenance. We describe typical use cases under solutions. Our cost calculators give initial estimates. Key terms are in the IT glossary. Books and long-form guides appear on the publications page; deeper articles live under topics.
If you have questions about this article or want a non-binding discussion about your project, you can book a consultation or reach us via contact. We usually respond within one working day.
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