PVGIS vs Project Sunroof: Ultimate 2025 Comparison
Choosing the right solar calculator is crucial for making informed decisions about your solar energy
investment. In this comprehensive comparison, we'll analyze PVGIS vs Project Sunroof to
help you determine which tool best suits your solar planning needs.
What is PVGIS?
The Photovoltaic Geographical Information System (PVGIS) is a free web application that allows the user to get
data on solar radiation and photovoltaic system energy production, in most parts of the world. PVGIS was born
from an ambitious vision within the Joint Research Centre (JRC) of the European Commission and has evolved into
both a free institutional version and an advanced commercial platform.
PVGIS24 gave me the clarity I needed, according to users who rely on its precision for professional solar
analysis. The platform offers:
For detailed information about PVGIS capabilities, visit the comprehensive PVGIS solar calculator guide.
What is Google Project Sunroof?
Google's Project Sunroof is a free online tool that helps homeowners calculate solar energy potential based on
their roof structure and local weather patterns. It was created in 2015 by a group of Google Engineers led by
Carl Elkin.
Project Sunroof collects data from Google Maps and Google Earth to analyze a home's roof characteristics and
location. This includes roof size, orientation, shading, and angle information. The tool uses satellite imagery
and machine learning to provide basic solar estimates for residential properties.
Accuracy Comparison: PVGIS vs Project Sunroof
PVGIS Accuracy
Results are fairly accurate (on an annual basis) since both use large databases from long periods of time.
Research shows that PVGIS often delivers better results than the other two freely available tools for PV power
generation when compared to measurements of existing PV parks.
At the heart of PVGIS lies a massive compilation of solar irradiation data, collected over several decades and
constantly refined. Unlike the regional approximations used by other tools, PVGIS incorporates subtle local
variations that can make all the difference.
The PVGIS24 premium platform offers enhanced accuracy through:
- Advanced satellite data integration
- Detailed weather pattern analysis
- Precise local microclimate modeling
- Professional-grade financial calculations
Project Sunroof Accuracy Limitations
When it comes to solar potential analysis, Project Sunroof is a helpful tool. However, we're a little wary about
its accuracy when it comes to solar costs and incentives. A lot of Project Sunroof data hasn't been updated
since 2018.
For example, Google estimates that a solar system in Houston, Texas, would be about $26,000 after applying the
federal solar tax credit. Using internal solar data from 2024, EcoWatch found the average cost of a solar system
in Houston to be about $36,570. As you can see, the figure from Project Sunroof is more than $10,000—almost
50%—off.
Google states that the estimates provided by Project Sunroof are generally accurate within 10-15% for solar
potential, but financial estimates are significantly less reliable.
Geographic Coverage: Global vs Regional
PVGIS Global Reach
PVGIS provides information on solar radiation and photovoltaic system performance for any location in the world,
except the North and South Poles. The enhanced PVGIS24 calculator covers:
- Europe with highest precision
- Africa with detailed satellite data
- Asia with comprehensive coverage
- Americas with reliable estimates
- Oceania with accurate modeling
Project Sunroof Limited Coverage
Currently, the Google Project Sunroof data explorer is only available in the U.S. and Germany. This severely
limits its usefulness for international solar projects or global comparisons.
As of late 2020, the tool has covered more than 60 million roofs across all 50 states in the US, but expansion
has been slow.
Features and Capabilities Comparison
PVGIS Advanced Features
PVGIS offers comprehensive solar analysis capabilities:
Technical Analysis:
- Detailed solar radiation mapping
- Multiple PV technology comparisons
- System configuration optimization
- Tracking system analysis
- Shading impact assessment
Financial Modeling:
- ROI and IRR calculations
- Payback period analysis
- Cash flow projections
- Multiple financing scenarios
- Market fluctuation modeling
For professional financial analysis, the PVGIS financial
simulator provides investor-grade calculations.
Project Sunroof Basic Features
Project Sunroof calculates the estimated cost of installing a solar panel system and the potential energy savings
the homeowner can achieve. This includes information on the payback period and the estimated time to break even
on the investment.
However, these calculations are simplified and often outdated, making them less reliable for serious solar
investment decisions.
Data Quality and Sources
PVGIS Scientific Foundation
Each PVGIS update represents thousands of hours of validation and comparison with real data from existing
installations. This scientific rigor is what ensures the reliability of the estimates.
The platform utilizes:
- European Space Agency satellite data
- Meteorological station networks
- Ground measurement validation
- Continuous algorithm refinement
Project Sunroof Data Limitations
Project Sunroof also uses weather and solar savings data from the National Renewable Energy Laboratory (NREL), as
well as utility electricity rates, solar costs and tax credit data from other third-party sources.
However, according to Project Sunroof's changelog, it hasn't been updated since 2018, so some of the data may be
outdated due to new solar incentives or other changes.
User Experience and Interface
PVGIS Professional Interface
The PVGIS platform offers multiple access levels:
- Free PVGIS 5.3: Basic calculations with limited capabilities
- PVGIS24 Enhanced: Advanced interface with professional tools
- Premium Packages: Pro and Expert packages available through subscription
- Multi-language support (80+ languages)
- Detailed reporting capabilities
Users can access the free version through the PVGIS 5.3 page or upgrade
to enhanced features for professional analysis.
Project Sunroof Simplified Design
Google Project Sunroof is pretty user-friendly. You can get a quick, personalized solar analysis for your home
with just three simple steps.
While simplicity is an advantage for basic users, it limits the depth of analysis available for serious solar
planning.
Cost Analysis Accuracy
PVGIS Financial Precision
Unlike PVWatts, which provides a very basic financial estimation, PVGIS.COM offers a detailed and
investor-friendly analysis including:
- Real installation costs
- Maintenance expenses
- Component replacement schedules
- Panel degradation modeling
- Energy tariff evolution
Project Sunroof Cost Inaccuracy
Real-world testing reveals significant discrepancies:
Based on that input, here's what Project Sunroof estimated: "$8,000 savings estimated net savings for your roof
over 20 years." The utility rate at Greg's house is $0.137/kWh. Assuming Greg's system saves him a net of $8,000
would mean Project Sunroof estimates around 2,920 kWh per year. 2,920 kWh/year from a 4.8 kW array with very
little shading is a conservative estimate, to say the least.
Professional vs Consumer Focus
PVGIS: Professional-Grade Analysis
As Sofia, a solar engineer in Barcelona, explains: "Before PVGIS, we could only explore two or three
configurations due to time and tool constraints. Today, we can easily compare a dozen and identify the one that
truly maximizes project value for the client."
The platform serves:
- Solar installation professionals
- Energy consultants
- Investment analysts
- Research institutions
- Serious homeowners
For comprehensive technical documentation, visit the PVGIS
documentation center.
Project Sunroof: Basic Consumer Tool
Google's Project Sunroof is really cool. In fact, it's amazing. Using aerial imagery and proprietary tools, it
comes up with some fantastic and useful data previously unavailable. However, this data is better used on a
macro level in our opinion.
The tool is designed for:
- Homeowners seeking basic estimates
- Initial solar interest assessment
- General awareness building
- Lead generation for solar companies
System Configuration Options
PVGIS Comprehensive Modeling
PVGIS supports extensive system configurations:
- Fixed-mount systems
- Single-axis tracking
- Dual-axis tracking
- Building-integrated PV
- Ground-mount installations
- Various panel technologies
- Multiple inverter options
For an agricultural project in Portugal's Alentejo region, the question was whether to invest in solar trackers
rather than a fixed installation. The simulation revealed that the single-axis tracker offered a 27% production
gain over the fixed system, while the dual-axis added only 4% more.
Project Sunroof Limited Options
Since this is Project SunROOF and not SunGROUND, you won't get much useful information if your home falls in the
ground mount category.
Project Sunroof focuses solely on:
- Rooftop installations
- Standard panel configurations
- Basic orientation analysis
- Simple shading assessment
Data Export and Integration
PVGIS Professional Outputs
PVGIS24 provides comprehensive simulation reports in PDF format, offering detailed analysis and professional
documentation for solar projects.
Project Sunroof Limited Export
Project Sunroof offers minimal data export options, making it difficult to integrate with professional analysis
workflows or detailed project planning.
Real-World Performance Validation
PVGIS Validated Accuracy
Comparison of the experimental and PVGIS SARAH solar data shows that the yearly average daily POA irradiation in
Niš, obtained by PVGIS SARAH, is 18.07% lower than the experimental values obtained by the SensorBOX.
While showing some conservative bias, PVGIS maintains reasonable accuracy across different locations and
conditions.
Project Sunroof Field Performance
Let's look at actual production over the past few years. The following three charts are based on values generated
by Greg's system's energy production monitoring software, not the utility.
Field comparisons consistently show Project Sunroof underestimating production potential, particularly for
optimized installations.
Which Tool Should You Choose?
Choose PVGIS When:
- Serious Investment Analysis: You need accurate financial modeling and ROI calculations
- Professional Projects: You're an installer, consultant, or energy professional
- Global Locations: Your project is outside the US or Germany
- Advanced Configurations: You need to compare tracking systems or specialized setups
- Detailed Analysis: You require comprehensive technical and financial reports
- Multiple Scenarios: You want to compare different system configurations
Choose Project Sunroof When:
- Initial Curiosity: You're just beginning to explore solar possibilities
- US Residential: You have a simple rooftop project in the United States
- Basic Estimates: You need quick, preliminary calculations
- No Investment: You want free, basic information without detailed analysis
Future Developments and Updates
PVGIS Continuous Evolution
Several promising developments are expected in future versions: More advanced integration of hybrid systems
(photovoltaic + wind).
The platform continues to improve through:
- Enhanced satellite data integration
- Improved weather modeling
- Advanced shading analysis
- Expanded global coverage
Project Sunroof Stagnation
Since it launched in 2015, Project Sunroof has continued to update its algorithms, improving the accuracy of its
solar calculator tool over time. According to Project Sunroof's changelog, it hasn't been updated since 2018.
The lack of recent updates raises concerns about data freshness and tool reliability.
Frequently Asked Questions
Is PVGIS more accurate than Project Sunroof?
Yes, PVGIS generally provides more accurate estimates, especially for technical and financial analysis. Research
shows PVGIS delivers better results when compared to real-world solar installation performance data.
Can I use Project Sunroof outside the United States?
No, Project Sunroof is currently only available in the United States and Germany, severely limiting its global
usefulness.
Which tool is better for commercial solar projects?
PVGIS is significantly better for commercial projects due to its professional-grade analysis, multiple system
configurations, and detailed financial modeling capabilities.
Does PVGIS cost money to use?
PVGIS offers both free and premium versions. The basic PVGIS 5.3 is completely free, while PVGIS24 offers
enhanced features for professional users.
How often is Project Sunroof data updated?
Project Sunroof hasn't been updated since 2018, which affects the accuracy of its cost estimates and incentive
calculations.
Which tool provides better financial analysis?
PVGIS offers comprehensive financial modeling with ROI, IRR, and cash flow analysis, while Project Sunroof
provides only basic cost estimates that are often inaccurate.
Is Project Sunroof good for initial solar research?
Project Sunroof can be useful for very preliminary research in the US, but its outdated data and limited analysis
make it less reliable for serious decision-making.
Conclusion
In the PVGIS vs Project Sunroof comparison, PVGIS emerges as the clear winner for anyone serious
about solar energy analysis. While Project Sunroof may satisfy basic curiosity about solar potential, its
limited geographic coverage, outdated data, and simplified analysis make it inadequate for informed investment
decisions.
PVGIS.COM is undoubtedly the best option for a reliable, worldwide, and professional study. Whether you're a
homeowner planning a residential installation or a professional managing commercial projects, PVGIS provides the
accuracy, features, and global coverage necessary for successful solar planning.
For the most reliable solar analysis, start with the PVGIS24 enhanced calculator
or explore the free PVGIS 5.3 version to experience the difference
professional-grade solar analysis can make for your project.
PVGIS offers superior accuracy, global coverage, and professional-grade analysis, making it the definitive
choice over Project Sunroof for serious solar energy planning in 2025.
