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Understanding CAN CSA C370-13 (2018): Performance Testing and Verification of Grid-Tied Photovoltaic Inverters
A comprehensive overview of the Canadian standard for photovoltaic inverter performance, efficiency measurement, and compliance requirements.
Grid-tied photovoltaic (PV) inverters must demonstrate reliable performance, high conversion efficiency, and stable interaction with the utility grid. In Canada, the benchmark for evaluating such performance is the national standard CAN CSA C370-13 (2018) — Photovoltaic (PV) Inverters — Performance and Testing. This standard, first published in 2013 and reaffirmed in 2018, establishes uniform test methods for determining the electrical performance of grid-connected PV inverters. It is widely referenced by certification bodies, incentive programs, and utilities as a key requirement for product listing and grid interconnection approval.
This article provides a detailed technical overview of CAN CSA C370-13, including its scope, core technical requirements, implementation considerations for manufacturers and testing laboratories, and compliance pathways for the Canadian market.
1. Scope and Application
CAN CSA C370-13 applies to grid-tied photovoltaic inverters intended for low-voltage (<1000 V AC) utility-interactive systems. It covers both single-phase and three-phase units, typically up to 250 kW in rated output, although the test methods can be extended to larger systems. The standard explicitly excludes stand-alone (off-grid) inverters and battery-based energy storage systems, although it may be used as a reference for hybrid inverters operating in grid-tied mode.
Scope Note: CAN CSA C370-13 focuses on performance testing. It is intended to complement the safety requirements of CSA C22.2 No. 107.1 (for utility-interactive inverters) and interconnection standards such as IEEE 1547 and CSA C22.3 No. 9. Manufacturers seeking comprehensive certification often need to address all three domains.
The test methods defined in the standard are applicable to inverters that use synchronous or asynchronous power conversion stages and any type of maximum power point tracking (MPPT) algorithm. The standard does not prescribe pass/fail limits; instead it defines how to measure and report performance parameters, leaving specific threshold limits to referencing codes, incentive programs, or customer specifications.
2. Technical Requirements and Test Methods
CAN CSA C370-13 specifies a series of test procedures under controlled laboratory conditions. The key measured parameters include DC-to-AC conversion efficiency, MPPT accuracy, power factor, harmonic distortion, DC current injection, and response to abnormal grid conditions. The following sections highlight the most critical technical requirements.
2.1 Efficiency Measurement and Weighted Efficiency
Conversion efficiency is the most closely watched performance metric for PV inverters. The standard defines two efficiency values:
- Static efficiency: Measured at discrete, steady-state operating points.
- Canadian weighted efficiency (ηCSA): A single figure of merit that reflects the inverter’s performance under a realistic distribution of solar irradiance and ambient conditions typical of Canadian climates.
The weighted efficiency is calculated using Equation (1) below:
ηCSA = Σ (ki × ηi) (1)
Where ki are the weighting factors specified in Table 1 and ηi is the efficiency measured at each corresponding power level. The testing is performed at a nominal DC input voltage (typically the manufacturer’s rated voltage or at the voltage that yields the best efficiency) while maintaining the inverter within its normal operating temperature range.
| Power Level (% of rated output) | Weighting Factor (ki) | Measurement Tolerance |
|---|---|---|
| 10 | 0.04 | ±0.5 % of reading |
| 20 | 0.05 | ±0.5 % of reading |
| 30 | 0.12 | ±0.5 % of reading |
| 50 | 0.21 | ±0.5 % of reading |
| 75 | 0.53 | ±0.5 % of reading |
| 100 | 0.05 | ±0.5 % of reading |
Important: The weighting factors in Table 1 are reproduced based on common industry practice and are subject to verification against the official version of CAN CSA C370-13 (2018), which contains the authoritative values. Users should always confirm the most current edition and any amendments.
2.2 Maximum Power Point Tracking Performance
An inverter’s ability to accurately track the maximum power point of the PV array substantially affects overall energy yield. CSA C370-13 requires the MPPT efficiency to be measured under steady-state conditions (constant irradiance and temperature) and during dynamic conditions that simulate passing clouds and rapid irradiance changes. The test measures the ratio of the actual power extracted by the inverter to the theoretical maximum available power from the PV simulator.
- Steady-state MPPT efficiency (ηMPPT): Typically better than 99.5% for modern inverters.
- Dynamic MPPT efficiency: Evaluated using ramped irradiance profiles; deviations greater than 2% from the ideal maximum power may be flagged.
- MPPT voltage range: The inverter must demonstrate the ability to track the MPP across its specified DC input voltage range.
2.3 Power Quality and Grid Interaction
To ensure stable and safe grid connection, the standard also prescribes the measurement of:
- Power factor: Both magnitude and sign (leading/lagging) are measured at multiple output levels. Many local interconnection rules require a power factor between 0.9 and unity.
- Total harmonic distortion (THD): Current THD must be measured at rated output and at half load. Limits are usually set by the referencing standard (e.g., ≤5% THD per IEEE 1547).
- DC current injection: The DC component of the AC output current must not exceed 0.5% of the rated current to prevent transformer saturation.
- Response to grid anomalies: The test procedure includes verification of anti-islanding protection and response to voltage/frequency excursions, although detailed trip times are typically specified by the interconnection standard, not by C370-13 itself.
3. Implementation Highlights for Manufacturers and Testing Laboratories
For a product to be listed or certified for the Canadian market, testing to CAN CSA C370-13 is often required. Here are the key implementation considerations:
- Test facility requirements: The standard calls for a calibrated DC power supply (or PV simulator) with at least twice the inverter’s rated power, precision power analyzers (Class 0.5 or better), and environmental control to maintain ambient temperature within ±2°C.
- Reporting: A comprehensive test report must provide efficiency curves for at least three different DC input voltages (within the MPPT range), tabulated data at each power level, and the final Canadian weighted efficiency value.
- Product family considerations: Inverters sharing the same power stage design and control firmware may be tested as a representative model. However, significant differences in ratings or topology require separate testing.
Best practice: When preparing for certification, coordinate with an accredited testing laboratory (e.g., CSA Group, Intertek, UL) early in the design phase. Pre-compliance testing using an in-house PV simulator and power analyzer can help identify performance issues, such as poor MPPT tracking at low power levels, before the formal test campaign.
The standard also provides guidance on uncertainty analysis. The combined uncertainty in the weighted efficiency measurement must not exceed ±0.5% (absolute) at the 95% confidence level. Laboratories must maintain their measurement systems traceable to national standards.
4. Compliance, Certification, and Market Implications
CAN CSA C370-13 is not a standalone safety standard; it is a performance test standard. Its role in compliance programs varies by province and utility, but the following points are widely recognized:
- Product certification: When an inverter is certified to CSA C22.2 No. 107.1, the certification body often requires a supporting test report from C370-13 to demonstrate efficiency and performance characteristics. The report must be issued by an ISO/IEC 17025 accredited laboratory.
- Incentive programs: Many feed-in tariff and net metering programs (e.g., in Ontario, Alberta, British Columbia) use ηCSA to rank eligible inverters. A higher weighted efficiency can improve project economics.
- Utility interconnection agreements: While most utilities in Canada reference IEEE 1547 or CSA C22.3 No. 9 for interconnection, they may also ask for evidence of MPPT performance and power quality derived from C370-13 testing.
Compliance reminder: The 2018 reaffirmation does not introduce new technical requirements. However, manufacturers should verify that their test report is based on the current edition, because older reports referencing the 2013 edition only may need to be updated to reflect the reaffirmed text, especially if referencing codes have incorporated the 2018 version by reference.
As of 2026, a new edition of CSA C370 is under development (expected in 2027). The new version will likely align more closely with the global IEC 61683 framework and add testing for bidirectional power flow (battery-ready inverters). Manufacturers planning to introduce new products are advised to monitor these developments to ensure future compliance.
Frequently Asked Questions
Q: What is the difference between the Canadian weighted efficiency (ηCSA) and the CEC efficiency used in the United States?
A: The two metrics are conceptually similar — both weight efficiency at different power levels according to irradiance statistics — but the weighting factors used in CAN CSA C370-13 are specifically tailored for Canada’s lower average insolation and different seasonal distribution. While many modern inverters show only a fractional difference between the two values, the CSA weighting better reflects annual energy production in Canadian climate zones.
A: The two metrics are conceptually similar — both weight efficiency at different power levels according to irradiance statistics — but the weighting factors used in CAN CSA C370-13 are specifically tailored for Canada’s lower average insolation and different seasonal distribution. While many modern inverters show only a fractional difference between the two values, the CSA weighting better reflects annual energy production in Canadian climate zones.
Q: Who can perform testing in accordance with CAN CSA C370-13?
A: Testing should be conducted by a laboratory that is accredited to ISO/IEC 17025 for the specific test methods in the standard. Accreditation can be obtained from organizations such as the Standards Council of Canada (SCC) or a recognized international body. Self-testing by the manufacturer may be accepted by some programs, but the report must include a complete uncertainty analysis and, ideally, be witnessed by a third-party certification body.
A: Testing should be conducted by a laboratory that is accredited to ISO/IEC 17025 for the specific test methods in the standard. Accreditation can be obtained from organizations such as the Standards Council of Canada (SCC) or a recognized international body. Self-testing by the manufacturer may be accepted by some programs, but the report must include a complete uncertainty analysis and, ideally, be witnessed by a third-party certification body.
Q: Is CAN CSA C370-13 mandatory for inverter certification in Canada?
A: The standard itself is voluntary, but it is frequently referenced by mandatory safety and interconnection standards. Most major certification schemes (CSA C22.2 No. 107.1, UL 1741 for Canadian adoption) require the performance data to be generated according to CSA C370-13. In practice, achieving product listing without a C370-13 test report is nearly impossible for the Canadian market.
A: The standard itself is voluntary, but it is frequently referenced by mandatory safety and interconnection standards. Most major certification schemes (CSA C22.2 No. 107.1, UL 1741 for Canadian adoption) require the performance data to be generated according to CSA C370-13. In practice, achieving product listing without a C370-13 test report is nearly impossible for the Canadian market.
Q: Are there any updates planned for CSA C370?
A: The current edition is the 2013 version reaffirmed in 2018. CSA Group has initiated a revision project (expected publication in 2027). The update will likely include new test procedures for high-penetration grid support functions, improved MPPT dynamic tests, and guidance for inverters with integrated storage. Stakeholders can participate in the standards development process through the CSA technical committee.
A: The current edition is the 2013 version reaffirmed in 2018. CSA Group has initiated a revision project (expected publication in 2027). The update will likely include new test procedures for high-penetration grid support functions, improved MPPT dynamic tests, and guidance for inverters with integrated storage. Stakeholders can participate in the standards development process through the CSA technical committee.
This article was prepared for informational purposes in 2026. Always consult the official standard for binding requirements.