Monitoring Energy Production

Energy production is influenced by many external and internal factors: solar irradiance, temperature, orientation, component efficiency, and system configuration. Monitoring allows production to be quantified, compared, and explained.

Without measurement, it is impossible to distinguish between normal variability due to weather and abnormal behaviour caused by faults, degradation, or suboptimal settings.

Effective production monitoring starts with the right variables. These measurements provide the raw data needed to compute meaningful indicators.

Electrical Quantities

• Voltage (DC & AC): Indicates operating conditions and system state.
• Current: Directly linked to instantaneous power.
• Power: Instantaneous production (W).
• Energy: Cumulative production over time (Wh, kWh).

Environmental Quantities

• Irradiance: Incoming solar power per unit area.
• Module temperature: Strongly affects PV efficiency.
• Ambient temperature: Provides context for thermal behaviour.
• Wind speed: Influences module cooling.

Raw measurements become useful when combined into indicators that describe system performance in a normalised and comparable way.

• Instantaneous yield: Power per installed capacity (W/Wp).
• Daily, monthly, yearly yield: Energy per installed capacity (kWh/kWp).
• Performance ratio (PR): Actual output compared to theoretical output.
• Capacity factor: Actual energy versus maximum possible energy.

These indicators help separate weather-related variability from system-related issues.

Comparing production data with weather conditions is essential to interpret performance. High irradiance with low production often indicates a system issue, while low production on cloudy days is expected.

Temperature effects are particularly important: PV modules typically produce less power as their temperature increases, even under strong sunlight.

Long-term monitoring reveals gradual performance changes due to aging, soiling, or component degradation. Sudden deviations may indicate faults such as shading, inverter issues, or connection problems.

Detecting these effects early improves reliability and protects long-term energy yield.

The frequency at which data is collected influences the insights that can be extracted. High-frequency data reveals short-term dynamics, while aggregated data supports long-term analysis.

• Seconds to minutes: Inverter behaviour, cloud transients.
• Hourly: Daily production profiles.
• Daily to monthly: Seasonal trends and comparisons.

Production monitoring is only one side of the picture. Understanding how energy is consumed is essential to optimise self-consumption and system sizing.

Continue to Monitoring Consumption