Solar ROI Data Sources
PV Yield is a screening calculator. Data sources are chosen for practical global coverage, transparent assumptions, and easy replacement by user-provided project values.
Location and geocoding
Country and city lookup can use Open-Meteo geocoding and Wikidata city metadata to help users select a location and retrieve coordinates. Coordinates are used only to request weather or solar resource data. City lookup is a convenience feature; for project work, exact latitude and longitude are better than a city center.
Solar and weather data
PV Yield first attempts to use PVGIS where available because it is designed for photovoltaic performance estimates and can provide PV-oriented monthly values. If PVGIS data is unavailable or fails for a location, the calculator can fall back to NASA POWER climatology data for global solar radiation and meteorological estimates.
Weather datasets describe long-term resource, not future guarantees. Rooftop shading, dust, snow, module ventilation, local microclimate, grid outages, and installation quality can make real output differ from public datasets. Users should compare weather sources for larger projects and import custom monthly POA values when a trusted engineering model is available.
Tariff defaults
Retail self-use tariff and export tariff defaults are starting assumptions. Solar export value can vary by utility, customer class, state or province, contract date, policy program, net metering rule, net billing rate, and time-of-use period. The calculator marks estimated tariff values and lets users replace them with project-specific values.
System cost defaults
EPC cost defaults represent simplified installed-cost assumptions for early screening. They are not module prices. A complete project cost should include modules, inverter, racking, protection devices, cabling, design, labor, permits, interconnection, commissioning, monitoring, and reasonable contingency.
When to override defaults
- Use an installer quote for installed cost when available.
- Use the actual utility tariff or power purchase contract instead of a national default.
- Use exact coordinates and measured shading assumptions for a real site.
- Use custom POA data when a professional design tool has already modeled the array plane.
- Use local tax, incentive, and loan terms instead of broad placeholders.
Last reviewed: June 30, 2026. Default values are screening assumptions and should be replaced with local project data before investment decisions.