EN IEC 61724-1 Photovoltaic System Performance - Part 1: Monitoring

The “EN IEC 61724-1 Photovoltaic system performance - Part 1: Monitoring” standard, developed by the International Electrotechnical Commission (IEC) and later published as a European standard as part of harmonization efforts, describes the terminology, equipment, and methods for monitoring and analyzing the performance of photovoltaic (PV) systems. This standard also serves as a basis for other standards based on the collected data.

This standard defines the terminology, required equipment, measurement methods, data collection procedures, quality controls, and key performance metrics to ensure consistent and reliable evaluation of PV system operation.

This standard provides a framework for performance monitoring and analysis of grid-connected PV systems and, increasingly, utility-scale and commercial installations. It helps stakeholders such as system owners, operators, investors, operation and maintenance providers, and financiers to fairly compare systems, identify underperformance, and support contractual guarantees (e.g., performance rate commitments).

This standard forms the basis for the related standards in the EN IEC 61724 series.

This standard defines two accuracy classes for PV performance monitoring systems:

• Class A: High accuracy (recommended for large/network-scale systems, performance guarantees, or detailed analysis):
• The strictest requirements for sensor accuracy, installation, calibration, and maintenance.
• Heated/ventilated pyranometers are required (to prevent dew/frost formation on the sensor dome and to ensure high data availability even in cold/humid conditions).
• High-resolution data recording (e.g., 1-minute intervals are recommended).
• More frequent quality control checks and backup measurements in larger systems.
• Class B: Medium accuracy (suitable for smaller commercial or residential scale systems where cost is a more important factor):
• More manageable sensor and maintenance requirements compared to Class A.
• It still provides reliable performance metrics, but has wider uncertainty tolerances.

Monitoring system providers must declare the accuracy class achieved by their installations, based on both hardware and operational procedures (not just sensor class).

The basic parameters measured and calculated according to this standard are as follows:

• Environmental parameters: Plane-array radiation, ambient/module temperature, wind speed.
• Electrical parameters: DC and AC power, voltage, current, energy efficiency.
• Performance metrics:
• Performance ratio: This is the most important key performance indicator, comparing actual efficiency to theoretical efficiency under reference conditions (temperature-corrected variants for bipolar systems).
• Temperature-corrected performance ratio.
• Other derived indices such as operating time, availability, and pollution loss estimates.

Data quality controls (e.g., outlier filtering, gap filling) and uncertainty analysis are essential, especially for Class A data.

Practical applications of this standard include the following:

• For investors/financiers: To reduce uncertainty in energy forecasts, Class A monitoring is often required in energy purchase contracts or yield assessments.
• For operation and maintenance: It helps in the early detection of problems such as contamination, shading, inverter failures, or malfunctions.
• Sensor examples: High-quality thermopile pyranometers are generally required for Class A compliance (ISO 9060 Class A certified, with ventilation/heating capabilities).

This standard plays a central role in professionalizing the performance evaluation of the solar energy sector as PV installations continue to grow globally.

In short, the EN IEC 61724-1 standard is necessary because the solar photovoltaic (PV) industry has grown enormously in terms of scale, complexity, and financial risks, creating a strong need for consistent, reliable, and comparable performance data across projects worldwide.

Without a unified international framework, performance monitoring varies widely, with different stakeholders using different sensors, measurement methods, data ranges, quality controls, and different ways of calculating key metrics such as performance rate. This leads to inconsistencies, disagreements over underperformance, unreliable yield estimates, and difficulties in verifying contractual warranties.

This standard has become indispensable for the following reasons:

• Standardization and comparability: As PV has evolved from small residential installations to massive grid-scale plants, investors, banks, asset owners, and operators have needed head-to-head comparisons. This standard provides a common language, terminology, and methodology to enable meaningful comparison of performance data from diverse installations.
• Risk mitigation in high-value investments: Solar energy projects require significant capital. Incorrect or incomplete monitoring increases uncertainty in energy yield estimates, leading to higher financing costs or disputes. The standard's accuracy classes (Class A, especially for grid-scale installations), high-quality sensors, backup measurements, regular calibration, and rigorous data quality procedures minimize this and directly reduce financial risk.
• Early detection of poor performance and optimization of operation and maintenance: PV systems can suffer from contamination, shading, inverter issues, degradation, or improperly accounted-for double-sided back-side gains. Without standardized monitoring, problems go unnoticed for longer. This standard enables operators to quickly identify and correct problems by defining what needs to be measured (e.g., array plane irradiation, module temperature, wind), how often it needs to be measured, and how the data should be processed (filtering, gap filling, uncertainty analysis).

As a result, the EN IEC 61724-1 standard has transformed what was once inconsistent, vendor-specific monitoring into a globally accepted, defensible practice that builds trust, reduces costs through better operation and maintenance, and supports the rapid scaling of solar energy worldwide.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services compliant with the EN IEC 61724-1 standard.