PV GIS Output & Savings Calculator
Use this calculator to estimate annual photovoltaic production using core GIS-style inputs such as solar resource, site losses, and orientation quality.
What this photovoltaic GIS calculator does
A photovoltaic geographical information system calculator estimates how much electricity a solar array can generate at a specific location. It combines spatial context (solar resource, terrain influence, orientation potential, and shading) with engineering assumptions (panel efficiency, performance ratio, inverter efficiency, and thermal losses).
This page is designed for pre-feasibility screening. It helps homeowners, energy analysts, and project developers answer questions like:
- How much energy could this roof or land parcel produce each year?
- What is the expected specific yield (kWh per kWp)?
- How sensitive is production to shading and orientation?
- What annual utility bill savings are plausible?
Core methodology used in this calculator
The model uses a straightforward annual energy equation. This is not a full hourly simulation, but it provides a reliable first-pass estimate:
Where combined derate includes:
- Performance ratio
- GIS access/orientation factor
- Shading loss
- Temperature loss
- Inverter efficiency
The calculator also derives system DC size from area and module efficiency, then computes capacity factor and specific yield. These two metrics are useful for comparing sites even when system sizes differ.
Input guidance for better results
1) Solar irradiance (kWh/m²/day)
Use long-term climatology values where possible. If you have monthly data, use annual average for this simplified model. Most regions fall between 3.0 and 6.5 kWh/m²/day.
2) GIS access/orientation factor
This is where geographic analysis matters. It can represent slope, azimuth mismatch, horizon obstruction, and nearby built-form impacts. A clean south-facing roof in many northern hemisphere regions may be near 95–100%, while a suboptimal orientation might be 75–90%.
3) Loss terms
Keep losses realistic. Overly optimistic assumptions are the most common planning error. Even excellent systems experience thermal and conversion losses.
How GIS improves photovoltaic planning
Traditional “back-of-the-envelope” solar estimates ignore spatial detail. GIS-based workflows improve decisions by layering:
- Satellite-derived solar irradiation maps
- Digital elevation models and terrain shading
- Roof segmentation and orientation classification
- Vegetation and obstruction detection
- Grid proximity and infrastructure constraints
By combining these inputs early, you can quickly rank candidate sites before committing to costly detailed engineering studies.
Interpreting results correctly
Use the outputs as a planning range, not an exact prediction. Weather variability, installation quality, maintenance cycles, and inverter clipping can shift actual performance. In practice, many analysts pair this annual estimate with:
- Hourly simulation tools
- On-site shade audits
- Local utility tariff modeling
- Degradation assumptions over 20–30 years
Best practices before investment
- Validate irradiance from at least one trusted solar atlas.
- Run low/base/high scenarios for losses and electricity price.
- Check structural and electrical constraints for rooftop projects.
- Model incentives, net metering, and export limitations separately.
- Obtain detailed design from a qualified solar professional.
Conclusion
A photovoltaic GIS calculator gives a practical bridge between map-based site intelligence and financial decision-making. If you feed it high-quality data and conservative assumptions, it becomes a powerful first filter for project viability.
Note: This calculator is for educational and planning use. It does not replace licensed engineering design, utility interconnection studies, or permitting review.