If you own solar panels, you’ve probably asked yourself: should I sell my excess energy back to the grid, store it in a battery, or just use it? The answer changes every day based on weather, grid demand, and rate structures. That’s exactly the problem the Solar Power Index (SPI) was built to solve.
What is the Solar Power Index?
The SPI is a proprietary metric developed by Soladex that forecasts the optimal way to use your solar energy each day. Think of it as a weather forecast, but for your energy decisions. By analyzing multiple data points in real time, the SPI gives you a simple, actionable recommendation.
How Does It Work?
The SPI combines several factors to generate its daily forecast:
Local Weather Data: Cloud cover, temperature, and humidity all affect your panel output. The SPI integrates hyper-local weather forecasts to predict your system’s production with remarkable accuracy.
Grid Rate Structures: Time-of-use rates mean electricity prices change throughout the day. The SPI factors in your utility’s rate schedule to identify the most valuable times to export or consume energy.
Historical Performance: Your system’s past production data helps the SPI calibrate its predictions to your specific setup — accounting for panel age, orientation, shading, and more.
Making It Actionable
Rather than drowning you in data, the SPI distills everything into a clear daily recommendation:
- High SPI: Great production day — consider selling excess back to the grid when rates peak
- Medium SPI: Moderate production — use energy as you generate it, store what you can
- Low SPI: Below-average production expected — draw from storage or shift heavy usage to off-peak hours
Getting Started
Setting up your SPI forecast takes just minutes. Connect your solar monitoring system (Enphase, Tigo, or others), enter your location and utility provider, and Soladex handles the rest. Your first forecast arrives the next morning.
The beauty of the SPI is its simplicity. You don’t need to understand grid economics or meteorology — just check your daily index and follow the recommendation. It’s solar energy management made accessible to everyone.
