Using PVGIS to Estimate Photovoltaic Production: The Guide That Turns Data into Informed Decisions

When I installed my first solar panels about ten years ago, I wished I had a tool like PVGIS. At the time, production estimates were more art than science, with approximations that could vary greatly depending on the installers. Today, PVGIS completely changes the game, offering remarkable accuracy accessible to everyone. Whether you are an experienced professional or a curious homeowner wanting to know the solar potential of your roof, this guide will help you use this powerful tool that turns complex data into concrete decisions.

The Journey of a Successful Solar Simulation

The first time I used PVGIS for a residential project in southern France, I was struck by how easily one could obtain highly accurate results. My client, skeptical about the potential yield of their installation, was convinced by the rigor of the data presented. What makes PVGIS so powerful is precisely this ability to turn uncertainty into confidence.

Let's start at the beginning: PVGIS is not just a simple calculator. It is the result of decades of research and data collection by the Joint Research Centre of the European Commission, enriched by global scientific contributions. The commercial version PVGIS24 pushes this expertise even further by adapting it to the specific needs of solar professionals.

First Steps on PVGIS: More Than Just an Address

The magic of PVGIS begins with precise location. Unlike other tools that rely on approximate regional data, PVGIS offers several ways to locate:

The full address is often the most natural starting point. I noticed that in some rural areas of Southern Europe, it can be better to use GPS coordinates directly for optimal accuracy. A Spanish installer recently told me that this precision allowed him to identify an area in his municipality where irradiation was significantly more favorable, information he was able to leverage with his local clients.

Automatic geolocation can also be used if you are physically on the site—especially useful during preliminary technical visits. I make it a habit to systematically verify these data on-site with my clients, which strengthens their confidence in the process.

System Choice: Where Expertise Makes the Difference

Once the location is established, PVGIS invites you to define your photovoltaic system. This is where the tool reveals its depth:

The mounting type greatly influences results. One day, while comparing two options for a country house in Tuscany, I was able to demonstrate that a two-pitched east-west system would produce only 8% less than a south-facing system but with a much more balanced production distribution throughout the day—a decisive argument for this client working from home.

Peak power is obviously fundamental, but PVGIS goes beyond the simple figure. Playing with different configurations for a commercial project in Portugal, we discovered that increasing power by 15% generated only 9% more production due to space and shading constraints. This nuance, impossible to perceive without detailed simulation, helped optimize the investment.

Inclination and orientation are often dictated by existing architecture, but not always. For a ground installation in Bavaria, we used PVGIS to compare more than 20 different combinations, discovering that a slightly westward (15°) orientation maximized production during the local grid’s peak hours, thus increasing the economic value of the electricity produced.

Advanced Parameters: The Professionals’ Secret

What truly distinguishes occasional users from experts is mastery of PVGIS’s advanced parameters. These options, often overlooked, can radically transform the relevance of a simulation:

System losses are generally underestimated in simplistic calculators. An experienced installer told me he systematically adjusts this parameter according to the building's age and the quality of existing electrical equipment. In an old mill converted into a home in southern Spain, this attention to potential losses allowed anticipating electrical upgrade works that would otherwise have compromised the system's performance.

The choice of meteorological database may seem technical but directly influences result reliability. For a project in the Alpine mountains, the difference between PVGIS-SARAH and PVGIS-ERA5 databases showed nearly a 7% gap in the estimated annual production. After checking with existing installations in the region, we determined which better reflected the specific local conditions.

Custom horizon is a feature I systematically use for sites surrounded by terrain or tall buildings. For an urban installation in Barcelona, precisely considering surrounding buildings revealed that the early morning production hours would be compromised, crucial information to adapt the sizing of the associated storage system.

Interpreting Results: The Art of Turning Data into Decisions

Getting PVGIS figures is only the first step. Interpreting these results is the real added value:

Beyond Annual Production

Total annual production is obviously the figure that immediately attracts attention. Yet, the monthly distribution hides the most valuable information. For a secondary residence in Provence mainly occupied in summer, we demonstrated that production perfectly matched occupancy periods, reinforcing the argument for self-consumption.

Seasonal variability also reveals surprises. A German client was convinced his installation would be unproductive in winter. PVGIS simulations showed that with a steeper tilt (60°), he could maintain decent production even during the darkest months, partially compensating for his electric heating system’s increased consumption.

Economic Analysis: The Universal Language

PVGIS24 turns kilowatt-hours into euros, dollars, or any other currency—a vital translation for most decision-makers. The integrated economic analysis allows visualizing:

The return on investment calculated by PVGIS takes into account parameters often overlooked. For an agricultural project in Andalusia, we integrated seasonal electricity price variations, revealing a payback period 14 months shorter than the client's initial estimates.

The evolution of savings over 25 years offers a long-term perspective that is essential. I noticed this graph strongly resonates with clients concerned about the sustainability of their investment. For a family business in Italy, this projection was the decisive factor, clearly showing how the solar installation would become a significant financial asset for the next generation.

The Nuances Only PVGIS Reveals

Some valuable information is only accessible thanks to PVGIS’s depth of analysis:

The impact of temporary shading is often underestimated. For a residential project near Munich, the simulation revealed significant production loss late in the afternoon due to a nearby grove of trees. This information allowed adapting the microinverter configuration to minimize the impact on the entire system.

Progressive performance degradation is integrated into PVGIS24 calculations, offering a realistic vision of system evolution over time. For an institutional investor considering a portfolio of solar projects in France, this precise projection helped refine financial models and secure more favorable financing.

Concrete Cases That Speak for Themselves

Numbers come alive through real examples. Here are some situations where PVGIS made all the difference:

Comprehensive Energy Renovation

Marie and Thomas were renovating their country house in the Luberon. Initially skeptical about the solar potential of their east-west roof, they were surprised by PVGIS simulation results. Not only did the estimated annual production cover 70% of their projected consumption, but the distribution of this production corresponded remarkably well to their consumption profile while working from home. What seemed like an architectural constraint turned out to be an advantage in their particular case.

Professional Optimization

Carlos, a solar installer with 15 years of experience in Valencia, uses PVGIS24 as a commercial differentiation tool. "Before, I spent hours explaining why my estimates were more reliable than the competition’s. Now, I present customized PVGIS simulations directly, and the conversation immediately moves to equipment quality and service." His conversion rate has increased by 23% since he systematically includes these detailed reports in his commercial proposals.

Informed Investment Decision

For a community solar energy project near Frankfurt, the citizens' committee hesitated between two potential sites. PVGIS simulations not only quantified the production difference (marginal, at 3%) but highlighted complementary production profiles. The final decision? Develop both sites with differently optimized systems, thus maximizing the value of electricity produced for the local community.

Avoiding Common Pitfalls: Experience Speaks

After hundreds of PVGIS simulations, I identified some common mistakes even experienced users can make:

Approximate geographic precision:

An error of a few kilometers may seem negligible, but in some mountainous or coastal regions, it can cause significant variations in estimates. A project in the Swiss Alps saw its production forecast drop by 12% after precise coordinate correction—a difference that would have compromised its economic viability if not identified before installation.

Forgetting local obstacles:

PVGIS integrates general topographic data but not specific obstacles like neighboring buildings or vegetation. I systematically complement simulations with a custom horizon analysis, especially in urban areas. This precaution saved a project in Lisbon where a new real estate development would create significant shading not accounted for in the standard simulation.

Neglecting advanced parameters:

PVGIS default settings are robust but not always optimal for your specific situation. System losses, for example, vary considerably depending on equipment quality and installation environment. For a project in a Mediterranean coastal zone, adjusting parameters to account for potential salt corrosion allowed setting realistic expectations and selecting equipment adapted to these particular conditions.

Conclusion: PVGIS as a Decision Partner

PVGIS is not just a calculator—it is a true decision partner for any photovoltaic project. Its wealth of data, flexibility, and accuracy make it an essential tool, whether you are a curious homeowner or a professional seeking to optimize complex installations.

Experience has taught me that PVGIS’s real value lies in its ability to turn uncertainty into confidence. Each simulation tells a unique energy story, revealing opportunities that more generic approaches could never identify.

As we collectively move toward a more sustainable energy future, tools like PVGIS democratize access to expertise once reserved for specialists. Whether your next solar project is modest or ambitious, let PVGIS illuminate your path toward optimal and personalized energy decisions.

This article was written in collaboration with professional solar installers and PVGIS users across Europe, North America, and South America. Their concrete experiences and practical advice enriched every section of this guide.