PVGIS vs Project Sunroof: Ultimate 2025 Comparison

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:

• PVGIS 5.3: The free version with limited capabilities
• PVGIS24: The enhanced calculator found on PVGIS.COM with advanced features and modern interface

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.