Technical inspections
Technical inspections, construction progress monitoring and due diligence for PV systems and battery storage – from construction to operation.
SONNWINN
Independent experts for photovoltaics and energy storage
Photo: DroneWize
Independent expertise
From the first project idea to ongoing operation: independent engineering, consulting and expert assessments for photovoltaics and battery energy storage (BESS).
Are you planning a solar park or battery storage system, do you need an expert report, or would you like an existing system inspected? Get in touch. At SONNWINN, experts and engineers from different disciplines work under one roof – you have one point of contact who supports your project from the very beginning.
Services
All services at a glance →
Assessments
Expert reports for permitting procedures, for financing (bankable) and for disputes.
Planning and consulting
We support you in the planning and design of PV and storage projects in an advisory or executing role, including with our own planning services: from the selection of components to tendering and construction supervision.
Planning and design
Sound planning is the foundation for technically and economically successful photovoltaic and battery storage projects. From the first feasibility assessment through technical concept and simulation-based design to the tender, we support you along the way.
In doing so, we take a holistic view of technical requirements and the economic framework. For battery energy storage systems (BESS) in particular, we combine technical design, operating strategies and revenue forecasts to develop suitable system configurations and assess their economic viability.
Our experience from technical inspections, expert reports and due diligence processes feeds directly into the planning.
- Site assessments, feasibility studies and preliminary design
- Technical concept and system planning
- Yield forecasts and simulations for photovoltaic systems
- Sizing and simulation-based design of battery energy storage systems (BESS)
- Revenue forecasts, operating strategies and economic viability analyses
- Scenario analyses, sensitivity studies and comparisons of variants
- Grid connection concepts and technical connection planning
- Component selection, bills of quantities and tender documents
From the first analysis to decommissioning
We support you in every phase of your project – with independent advice, sound planning, technical inspections and expert reports, tailored to your individual requirements.
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Analysis
Assess site, yield and revenues before the investment.
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Planning and permitting
Evidence for the permitting procedure, design and tendering.
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Construction and commissioning
Inspect the construction work, document acceptance with measurements.
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Operation
Keep track of condition and yields, assess defects and damage.
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Decommissioning or repowering
Quantify decommissioning costs, assess continued operation or renewal technically.
Projects in Germany and worldwide
Throughout Germany and in more than 25 other countries, we have planned, assessed and technically inspected projects. The maps show a selection of the places where we have worked.
- Assessments
- Technical inspections
- Planning and consulting
About SONNWINN
SONNWINN grew out of a network of experts and engineers from the solar industry, some of whom have been working in photovoltaics for more than 20 years. In May 2025 we founded SONNWINN GmbH from this network. It is the heart of the network: this is where your projects come together, and this is where you have your permanent point of contact.
From the network, we bring in exactly the expertise your project needs – pooled in a single point of contact.
Our head office is in Wedel near Hamburg; our experts have further locations in Lower Saxony, Hesse and Bavaria. We work throughout Germany and internationally.
Frequently asked questions
What does SONNWINN do?
SONNWINN is a team of independent experts and engineers for photovoltaics and electricity storage. We inspect installations technically, prepare expert reports – for example for permitting procedures, banks, warranty cases and disputes – advise on planning and design and also carry out planning ourselves.
Where does SONNWINN work?
Our head office is in Wedel near Hamburg. Our experts have further locations in Lower Saxony, Hesse and Bavaria. We work on projects throughout Germany and internationally, so far in more than 25 other countries.
What does an assessment or inspection cost?
Costs depend on scope and question; you receive a quote in advance.
What does the name SONNWINN mean?
The name comes from Old High German: “sunn” (sun) and “wini” (friend), literally “friend of the sun”.
Enquiry
Use the form, call us on +49 4103 121 4221 or write to kontakt@sonnwinn.de – whichever suits you best.
You do not need to attach documents to your enquiry – once we have received it, we will help you put together the documents required.