About
Forecast.Solar provides developers, homeowners, and energy professionals with a reliable RESTful API to forecast solar photovoltaic (PV) energy production. By combining historic solar irradiation data from the EU's Photovoltaic Geographical Information System (PVGIS) with live weather forecasts from multiple providers, the platform delivers highly accurate estimates of solar power output in watts and watt-hours. Users supply their panel's geographic coordinates, tilt (declination), and azimuth (orientation), and the API returns forecasts for up to 7 days with resolutions down to 15 minutes on professional accounts. The free tier covers basic solar production estimates, while professional accounts unlock weather data (sky coverage, temperature, wind), time windows for smart load automation, embeddable chart widgets, and CSV/XML/JSON response formats. Data coverage is global thanks to PVGIS 5.2, making the service suitable for installations across Europe, Africa, Asia, the Americas, and beyond. A Swagger-compatible API definition simplifies integration, and a Swagger-UI playground lets developers build and test requests interactively. Ideal use cases include home energy management systems, EV charging schedulers, battery storage optimization, smart home automation, solar monitoring dashboards, and grid-tied system planning. Forecast.Solar is well-suited for IoT developers, energy analysts, and prosumers looking to maximize self-consumption of solar energy.
Key Features
- Solar Production Forecasting: Delivers watt and kWh estimates for up to 7 days at 1-hour or 15-minute resolution, combining PVGIS historic irradiation data with live cloud-coverage and temperature forecasts.
- Weather Data Endpoint: Professional accounts can retrieve sky coverage, textual weather conditions, icons, temperature, and wind data alongside production forecasts.
- Smart Load Time Windows: Automatically identifies optimal time windows for switching controllable loads (EV chargers, heat pumps, etc.) based on forecast surplus solar energy.
- Embeddable Chart Widgets: Generate daily solar forecast charts with simple JavaScript snippets, supporting today/tomorrow, historic averages, and clear-sky theoretical production views.
- Global Coverage via PVGIS 5.2: Supports solar installations almost anywhere in the world thanks to the latest PVGIS 5.2 radiation database update.
Use Cases
- Integrate solar production forecasts into a home energy management system to automatically shift appliance usage to peak solar hours.
- Build a battery storage optimization app that charges batteries during forecast surplus periods and discharges during low-production windows.
- Schedule EV charging sessions to coincide with predicted high solar output, maximizing use of self-generated renewable energy.
- Create a solar monitoring dashboard for prosumers that displays 7-day production forecasts alongside historic averages and clear-sky benchmarks.
- Automate smart-grid or IoT loads by querying the time windows endpoint to trigger controllable devices only when solar generation is at its peak.
Pros
- Easy API Integration: Simple RESTful endpoints with Swagger-UI testing, JSON/CSV/XML responses, and a Swagger-compatible YAML definition make integration fast for developers.
- Global Data Coverage: PVGIS 5.2 provides near-worldwide solar irradiation data, making the API useful for installations across most of the globe.
- Free Tier Available: Basic solar production forecast data is available on the free plan, lowering the barrier for hobbyists and small projects.
- High-Resolution Forecasts: Professional accounts receive 15-minute granularity data up to 7 days ahead, enabling precise energy management decisions.
Cons
- Advanced Features Behind Paywall: Weather data, time window automation, chart widgets, and 15-minute resolution all require a paid Professional account.
- Accuracy Depends on Weather Station Proximity: Forecast quality may degrade in regions with sparse weather stations, as the API notes a possible offset for locations far from measurement points.
- Occasional Service Interruptions: As a smaller API provider, the service has experienced maintenance-related outages, which may affect production-critical integrations.
Frequently Asked Questions
What data do I need to get a solar forecast?
You need your solar panel installation's latitude and longitude, the tilt angle (declination) of the panels, their azimuth orientation (e.g., 0 for south), and the system's peak power in kilowatts.
How far ahead can Forecast.Solar predict solar production?
The API provides forecasts for up to 7 days into the future. Free accounts typically receive hourly resolution, while professional accounts can access 15-minute resolution data.
What formats does the API support?
The API can return data in JSON, CSV, or XML formats, giving developers flexibility to integrate with virtually any platform or programming language.
Is there a free plan?
Yes, the free tier includes solar production forecast data (watts and watt-hours). Weather forecasts, time windows, chart widgets, and higher resolution data require a Professional account.
Which regions are covered by Forecast.Solar?
Thanks to PVGIS 5.2, coverage extends to almost the entire world, including Europe, Africa, Asia, the Americas, and Oceania.
