Valuing existing systems – what really matters with operating solar parks
How to value an operating solar park properly: yield history, remuneration, condition of the technology, contracts and the purchase price per kilowatt peak in context.
Fabian BökeWhy existing systems follow a logic of their own
To many investors, existing systems at first seem simpler than new projects. The system is there, it produces electricity, the yields are visible. Compared with project rights or construction schemes, the risk appears lower.
In practice, however, only the kind of question shifts. While with new projects the uncertainty lies in the future, with existing systems it often lies in the details of the past.
A solar park that has been running for years brings data with it. And it is exactly this data that has to be put into context.
Yield data – between reality and interpretation
The biggest advantage of an existing system lies in its real yields. They show what was actually produced – not what would theoretically be possible.
At the same time, practice shows that there are regularly deviations between simulated and actual yields. In the projects evaluated, these often lie in the range of about −3 to −10 % compared with the original simulations. In individual cases, however, the deviations can be considerably larger – with observed outliers of more than −20 %.
These differences rarely arise from a single factor, but from the interplay of several influences. Weather deviations, soiling, system losses not fully captured or operational downtime often have a stronger effect in reality than models depict.
What matters is therefore not whether a simulation is "right", but how it is put into context. Yield models provide orientation – the actual performance of a system only shows in operation.
For the valuation this means: Real yield data is the most reliable yardstick, but should always be viewed in context. A single year can distort as much as an over-optimistic simulation. Only over several years does a robust picture emerge that allows conclusions about the actual performance of a system.
Valuation method – how existing systems can be assessed in a structured way
Practice has shown that the valuation of existing systems is only robust if it is carried out systematically. Individual key figures or isolated views are not enough to obtain a complete picture.
A well-founded assessment usually rests on three central dimensions.
First, the technical history is the focus. What matters is not only which components were installed, but how they have developed over the years. Modules, inverters and monitoring systems provide valuable clues here – especially when maintenance, failures and deviations are traceably documented. Technical assessments often follow standardised appraisal procedures that place the current condition in a long-term context.
The second dimension is the contractual structure. Leases, grid connection agreements, easements and any existing marketing contracts form the legal foundation of the system. Their quality decides how stably the project can be operated in the long term. In practice, site plans, lease and right-of-way constellations and existing direct marketing agreements, among other things, are reviewed and assessed.
The third level is the financial valuation. It goes beyond simple return calculations and is based on conservative assumptions. Models built on NPV and IRR logic make it possible to assess economic viability under different scenarios. What matters is not the optimisation of an individual case, but the question of how robust a project remains under realistic conditions.
Only the interplay of these three perspectives produces a picture robust enough to base investment decisions on.
Conclusion – existing systems are understood through structure and history
An existing system cannot be valued on numbers alone. It has to be read like a history.
Yields, technical development, contractual structure and operating history together form a picture far more meaningful than any single key figure.
This is exactly why a well-founded valuation is not carried out in isolation, but along clear review logics – technical, contractual and economic. Only when these levels are brought together does a realistic understanding of opportunities and risks emerge.
For investors this means: the quality of an existing system shows not in its current condition, but in the traceability of its development and the stability of its structure.
Whoever understands how a solar park is built and how it was operated can also judge how it will behave in future. And that is exactly the difference between an investment based on data – and one based on understanding.
More articles
Matching projects on the marketplace
Project rights, turnkey systems and existing systems, with the purchase price per kWp at a glance.
