How to Calculate Solar Panel Production for Free?
Calculating the solar panel production of your installation before making the investment is a crucial step
for any
solar project. Fortunately, numerous free tools are now available to accurately estimate the energy output
of your
future solar panels. In this comprehensive guide, we'll explain how to perform a reliable and precise
calculation to
determine solar panel production for free.
Why Calculate Solar Panel Production Before Installation?
Learning how to calculate solar panel production free represents much more than simple technical curiosity. This
estimation forms the foundation of any investment decision in solar energy. Without this preliminary analysis, it's
impossible to evaluate the real profitability of a solar project.
An accurate production estimate allows you to correctly size the installation according to your energy needs. It
also helps you choose the most suitable panel technology for your geographical location and architectural
constraints.
Moreover, these calculations are essential for evaluating different financial scenarios: self-consumption, total
sale, or a combination of both. This comparative analysis helps optimize return on investment and choose the most
profitable strategy.
Factors Influencing Solar Panel Production
Local Solar Irradiation
Solar irradiation is the primary factor determining photovoltaic installation production. This data varies
considerably depending on geographical location, ranging from 1,100 kWh/m²/year in northern regions to over
1,400 kWh/m²/year in southern areas.
Irradiation also depends on local climatic factors such as average cloud cover, altitude, and proximity to
bodies of water. These variations explain why two identical installations can show very different yields
depending on their location.
Panel Orientation and Tilt
The optimal orientation typically faces due south with a 30 to 35-degree tilt. However, southeast or southwest
orientations with variable tilts can also offer interesting yields.
A precise calculation to determine solar panel production free must integrate these parameters to provide a
realistic estimate. Differences can reach 20 to 30% between optimal and unfavorable orientations.
Shading and Obstacles
Shading constitutes one of the most impactful factors on photovoltaic production. Trees, neighboring buildings,
chimneys, or terrain features can significantly reduce installation performance.
Even partial shading on a string of panels can affect the production of the entire group. This is why shading
analysis must be particularly careful during calculation.
Technical Characteristics
The type of solar panels, technology used (monocrystalline, polycrystalline, thin film), and inverter quality
directly influence production. System losses (wiring, inverter, dust) must also be integrated into the
calculation.
Free Tools for Solar Panel Production Calculation
PVGIS 5.3: The Free Scientific Reference
PVGIS 5.3 represents the reference tool to calculate
solar panel production free in Europe. Developed by
European research organizations, this tool benefits from exceptional meteorological databases covering the
entire European territory.
The tool uses satellite and historical meteorological data spanning several decades to guarantee estimation
reliability. It automatically integrates seasonal variations, local climatic conditions, and geographical
specificities of each region.
PVGIS 5.3 allows calculating monthly and annual production while considering orientation, tilt, and photovoltaic
technology type. The tool also provides hourly data for users wanting to analyze production profiles in detail.
PVGIS24: Modern Evolution with Advanced Options
PVGIS24 offers a modern approach to solar panel production
calculation with a redesigned user interface. The
free version allows performing a complete calculation for one roof section with the possibility to export
results in PDF format.
This free version offers an excellent compromise for individuals wanting to obtain a professional report of
their production calculation. The intuitive interface guides users through different configuration steps, making
the tool accessible even to beginners.
The tool also integrates direct access to PVGIS 5.3 for users wanting to compare results or access raw data
without limitations.
Other Available Free Tools
Several other tools offer free photovoltaic production calculations. Google Project Sunroof uses Google Earth
data to analyze rooftops, but its geographical coverage remains limited in many regions.
Many solar panel manufacturers also offer their own calculators. These tools are generally easy to use but may
lack neutrality and scientific precision.
Methodology for Accurate and Free Calculation
Step 1: Basic Data Collection
Before starting your calculation to determine solar panel production free, gather essential information: precise
installation address, roof characteristics (available surface, orientation, tilt), and identification of
potential shading sources.
Also note your annual electricity consumption based on your last 12 months' bills. This data will help correctly
size the installation according to your actual needs.
Step 2: Using PVGIS for Basic Calculation
Start by using PVGIS 5.3 to obtain a reference estimate. Enter your location, define your roof's orientation and
tilt, then select the intended panel technology.
The tool will provide monthly and annual production estimates in kWh. This data forms the basis of your analysis
and can be supplemented by other calculations.
Step 3: Refinement with PVGIS24
Then use PVGIS24 to refine your calculation and obtain a detailed report. The free version allows exporting a
professional PDF document including all production data and parameters used.
This step is particularly useful if you plan to present your project to third parties (installers, financing
organizations, family).
Step 4: Cross-Validation
To guarantee calculation reliability, compare results obtained with other tools or calculation methods.
Significant discrepancies should be analyzed to identify sources of divergence.
Interpreting Solar Panel Production Results
Understanding Units of Measurement
Production results are generally expressed in kWh (kilowatt-hours) per year. This unit represents the amount of
energy your installation will produce in a typical year.
The Performance Ratio (PR) indicates overall installation efficiency considering all losses. A PR of 0.8 (80%)
is considered acceptable for a well-designed installation.
Analyzing Seasonal Variations
Photovoltaic production varies considerably with seasons. In many regions, summer production can be 4 to 5 times
higher than winter production. This variation must be considered in consumption or storage strategy.
Calculation tools generally provide monthly data allowing anticipation of these variations and optimization of
self-consumption.
Evaluating Shading Impact
Shading can reduce production by 5% to 50% depending on its importance and daily distribution. Advanced tools
help identify the most impacted periods and areas.
Financial Calculation Based on Estimated Production
Electricity Savings Estimation
Once production is calculated, you can estimate savings on your electricity bill. For self-consumption, multiply
self-consumed production by your supplier's kWh price.
This solar financial simulation allows
evaluating project profitability and calculating payback time.
Revenue Calculation from Sales
If you opt for selling all or part of your production, calculate revenue by multiplying sold production by the
current feed-in tariff.
Feed-in tariffs evolve regularly, so it's important to use the most recent rates for your calculations.
Return on Investment Evaluation
Combine electricity savings and sales revenue to calculate your installation's annual benefit. Divide the total
installation cost by this annual benefit to obtain payback time.
Optimizing Solar Panel Production
Choosing Orientation and Tilt
If you have flexibility in orientation or tilt, test different configurations with your calculation tool. A
slightly east or west orientation might be preferable if your consumption is offset from the solar production
peak.
Optimal Sizing
Use production results to correctly size your installation. Oversizing can reduce profitability if sales revenue
is lower than self-consumption savings.
Shading Management
If shading is identified, evaluate technical solutions: power optimizers, micro-inverters, or panel layout
modification.
Limitations of Free Calculations and Solutions
Estimation Accuracy
Free tools offer 85 to 95% accuracy for production estimates, which is largely sufficient for project
evaluation. However, certain local specificities may require additional analysis.
Complex Cases Requiring Advanced Tools
For complex rooftops with multiple orientations, ground-mounted installations, or projects with particular
constraints, more sophisticated tools may be necessary.
The paid plans of PVGIS24 offer advanced features
for these specific cases: multi-section analysis, detailed
financial simulations, and specialized technical support.
Validation and Results Refinement
Comparison with Existing Installations
If possible, compare your estimates with similar installation performance in your region. User associations or
local installers can provide reference data.
Professional Consultation
While free calculations are very reliable, validation by a qualified professional remains recommended,
particularly for large investments.
Regular Calculation Updates
Climatic, economic, and technological conditions evolve. Update your calculations periodically, especially if
the delay between study and installation extends.
Common Mistakes to Avoid
Self-Consumption Overestimation
Many users overestimate their self-consumption capacity. Analyze your consumption habits carefully to correctly
size the installation.
Neglecting System Losses
Losses due to inverter, wiring, dust, and panel aging can represent 15 to 20% of theoretical production. Ensure
your calculation integrates these losses.
Forgetting Interannual Variations
Weather conditions vary from year to year. Plan a safety margin in your financial projections to account for
these variations.
Future Developments in Production Calculation
Artificial Intelligence Integration
Future calculation tools will integrate AI algorithms to refine predictions by analyzing performance data from
real installations.
Real-Time Weather Data
Evolution toward forecasts based on updated meteorological data will improve estimation accuracy.
Coupling with Storage Systems
Next-generation tools will automatically integrate battery systems to optimize self-consumption and energy
independence.
Conclusion
The ability to calculate solar panel production free is now accessible to everyone through reliable scientific
tools like PVGIS 5.3 and PVGIS24. These tools provide accurate estimates at no cost, facilitating the evaluation
of any solar project.
The key to success lies in quality input data and correct understanding of obtained results. By following the
methodology presented in this article, you'll have all the necessary information to evaluate the feasibility and
profitability of your photovoltaic project.
Don't hesitate to use multiple tools to validate your results and have your conclusions confirmed by a qualified
professional before proceeding with installation. This prudent approach will guarantee you make the best
decisions for your solar investment.
FAQ - Frequently Asked Questions
Q: How reliable is a free solar panel production calculation?
A: Free tools like PVGIS offer 85 to 95% accuracy for production estimates, which is largely sufficient for
evaluating solar project feasibility.
Q: How long does it take to perform a complete calculation?
A: A basic calculation can be completed in 10 to 15 minutes with free tools. For thorough analysis with multiple
scenarios, allow 30 to 60 minutes.
Q: Do free tools account for shading?
A: PVGIS 5.3 and PVGIS24 integrate basic analysis of geographical shading (terrain, buildings), but detailed
analysis of nearby shading often requires on-site evaluation.
Q: Can you calculate production for different panel types?
A: Yes, tools allow selecting different technologies (monocrystalline, polycrystalline, thin film) and adjusting
performance parameters according to panel type.
Q: Should calculations be redone regularly?
A: It's advisable to update calculations every 6 to 12 months, particularly if project conditions evolve (roof
modification, consumption changes, tariff evolution).
Q: Do free calculations include system losses?
A: Yes, tools automatically integrate main losses (inverter, wiring, temperature) with standard values. For more
precise calculations, advanced versions allow adjusting these parameters.
Q: How do you validate result consistency?
A: Compare results from multiple tools, verify consistency with similar installations in your region, and
consult a professional for important projects.
Q: Do free tools allow calculating self-consumption?
A: PVGIS24 includes self-consumption calculation features in its free version, allowing estimation of the
production portion directly consumed according to your usage profile.
