The debate between the reliability of microinverters vs string inverters with optimizers, such as those offered by Enphase and SolarEdge, is a common topic in the solar industry.
Our extensive 10-year data repository on solar inverters, enriched with insights from our monitoring software, serves as a crucial resource for consumers deciding between microinverters and string inverters.
This data offers a detailed analysis of loss and claims ratios for hundreds of thousands of units, providing an empirical foundation for understanding the reliability, efficiency, and long-term performance of different inverter types.
Both systems have advantages and reliability claims, but our interest is in hard data on Mean Time Between Failures (MTBF) and overall reliability records.
Based on our internal data, microinverters have a higher average reliability score than string inverters.
Our data indicates that less than 1 in 800 microinverters experience failure in the first two years of operations, while approximately 1 in 350 string inverters fail. This suggests a higher reliability rate for microinverters in general.
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Microinverter Reliability
Microinverters display strong durability in the long term with a failure rate which is less than 1 in 800, indicating a high level of reliability. This aligns with the claims made by manufacturers like Enphase, who highlight the independence of each microinverter in a solar array.
Lower Heat Stress: Micro inverters handle lower power levels than string inverters. This results in less heat generation, a major cause of wear and tear in electronic components. Reduced heat stress contributes to longer lifespans and lower failure rates.
Simpler Power Conversion Process: Micro inverters directly convert the DC power from the solar panel to AC power at the panel site. This simpler and more direct conversion process can be inherently more reliable than the more complex process in string inverters, which must handle higher voltages and power levels.
If one microinverter fails, it does not impact the performance of the others, ensuring that the rest of the array continues to function effectively.
String Inverter Reliability
With a failure rate of about 1 in 350, string inverters are less reliable than microinverters, according to our data. This is due to a string inverter’s central role in a solar array. When a string inverter fails, it can affect the entire array or a significant portion.
String inverters often handle higher power loads than micro inverters. This can lead to more heat accumulation, which, over time, can stress the electronic components and lead to a higher likelihood of failure.
In Addition, String inverters operate at higher voltages, which can lead to more significant wear and tear over time compared to the lower voltage operations of micro inverters.
Power Optimizers
While specific MTBF data for optimizers isn’t provided, SolarEdge’s argument for their reliability hinges on their simplicity compared to microinverters.
However, it’s essential to note that while optimizers may be less complex, they still work in conjunction with a central string inverter. Therefore, the reliability of the string inverter still influences the overall reliability of a system with optimizers.
Overall Reliability Record:
According to your data, microinverters show a better reliability record in terms of lower failure rates. However, the overall reliability of a system also depends on factors like installation quality, environmental conditions, and system design.
It’s important to note that while MTBF is a useful indicator of component reliability, the actual performance can vary based on factors like installation quality, environmental conditions, and maintenance practices.
For a comprehensive understanding, it’s advisable to consult with solar energy professionals and consider independent third-party assessments or reviews that might offer broader insights into the long-term reliability of these systems.
Microinverter Advantages:
- Location: Attached directly to each solar panel.
- Functionality: They convert the DC electricity from each panel into AC electricity.
- Advantages:
- Individual Panel Optimization: Each panel operates independently, which means if one panel is shaded or underperforming, it does not affect the performance of other panels.
- Easier Expansion: Adding more panels is generally easier because each has its inverter.
- Longer Warranties: Typically come with longer warranties than string inverters. On average, about 25 Years
- Detailed Monitoring: Allow for detailed monitoring of each panel’s performance.
Disadvantages:
- Higher Cost: Generally, it is more expensive upfront than string inverters.
- Potential for More Points of Failure: There are more components that could potentially fail, as each panel has an inverter.
String Inverters Advantages
- Location: Typically installed at a central location, often near the electrical panel of the home or business.
- Functionality: They convert the DC electricity from a string (or strings) of solar panels into AC electricity.
- Advantages:
- Lower Initial Cost: Generally, it is less expensive upfront than microinverters.
- Simplicity: Fewer components to install and maintain.
- Disadvantages:
- Shading Impact: The performance of the entire string can be reduced if one panel is shaded or underperforming unless power optimizers are added.
- Less Flexible: Adding more panels can be more complex and may require additional or new inverters.
- Shorter Warranties: Typically have shorter warranties than microinverters.
- Less Detailed Monitoring: Usually, only whole-system performance is monitored, not individual panels.
The choice between microinverters and string inverters often depends on the specific needs of the solar energy system, including factors like budget, the layout and shading of the solar array, and the desire for detailed performance monitoring.
Long-Term Service Cost
The service cost of replacing a string inverter generally ranges from $500 to $600, with some variability depending on specific circumstances. Here’s a breakdown of the factors influencing these costs:
Standard Replacement Cost String Inverters:
The process typically involves 1-2 hours of labor and a truck roll (visit to the site) for a straightforward string inverter replacement. This scenario likely accounts for the typical service cost range of $500 – $600.
Diagnostic Visits:
The cost can increase if a technician needs to visit the site initially to diagnose the problem and then return to perform the replacement.
This additional labor and travel time can push the cost higher than the standard range.
Remote Diagnostics and Replacement:
Some string inverters can be diagnosed remotely, and if a replacement is necessary, the new inverter can be shipped directly, potentially saving substantial costs.
This approach avoids needing an initial diagnostic visit and can streamline the replacement process.
Microinverter Replacement Costs:
Comparatively, micro-inverter service calls are generally more expensive. The replacement process is more involved since it requires access to the roof, disconnecting, reconnecting, and removing the old microinverter, disconnecting electrical connections, and rewiring the new unit.
If a technician must remove multiple panels to access a faulty microinverter, this can further increase the cost. Additionally, companies like Enphase often require a technician to diagnose the issue on-site, which adds to the service time and cost.
In summary, the standard service cost for replacing a string inverter falls within a reasonable range and can be more cost-effective, especially when remote diagnostics and replacement are possible.
In contrast, microinverter replacements are generally more labor-intensive and expensive, particularly when multiple panels are involved or the manufacturer requires on-site diagnostics.
Is a micro-inverter better than a string inverter?
Whether a micro-inverter is “better” than a string inverter depends on your solar energy installation’s specific circumstances and needs. Here are some considerations to help determine which might be more suitable for your situation:
Shading and Panel Orientation:
If your solar panels are likely to experience partial shading or are installed on multiple roof planes with different orientations, micro-inverters can be a better choice.
They allow each panel to operate independently, minimizing the impact of shading or orientation differences on overall system performance.
System Expansion:
Micro-inverters offer greater flexibility for future system expansions or if you plan to start small and add more panels later. You can add panels individually without worrying about the capacity of a central inverter.
Monitoring and Maintenance:
Micro-inverters provide detailed monitoring at the panel level, which can be beneficial for identifying and troubleshooting individual panel issues. This can lead to more effective maintenance but might be overkill if you don’t need such detailed data.
Cost:
Initially, micro-inverters are generally more expensive than string inverters. This higher upfront cost can be a deciding factor, especially for larger installations where the cost difference can be substantial.
System Size:
For smaller or residential solar installations, the advantages of micro-inverters (like panel-level optimization and monitoring) are often more pronounced.
In contrast, for large commercial systems, the cost-effectiveness of string inverters might make them a preferred choice.
Longevity and Warranty:
Micro-inverters typically come with longer warranties than string inverters, which might be appealing if long-term reliability is a priority.
Safety:
Micro-inverters can offer a safety advantage as they convert DC to AC right at the panel, reducing the amount of high-voltage DC wiring.
Downsides
Both microinverters and string inverters have their respective downsides, which can influence your decision depending on your specific solar installation requirements:
Downsides of Microinverters:
Higher Initial Cost: Microinverters are generally more expensive upfront than string inverters. This higher cost can be significant, especially in larger installations.
More Complex Installation: Since a microinverter is attached to each solar panel, the installation process can be more complex and time-consuming than a single string inverter.
Potential for More Points of Failure: With a microinverter system, there is an inverter on each panel. This means more potential points of failure, which could increase the likelihood of maintenance issues over time.
Limited High-Power Options: Microinverters are typically used in residential or smaller commercial systems. For very large-scale installations, they might not be as feasible or cost-effective as string inverters.
Downsides of String Inverters:
Performance Reduction Due to Shading or Panel Mismatch: If one panel in a string is shaded or underperforming, it can reduce the performance of the entire string. This is particularly problematic in installations where panels are facing different directions or are subject to variable shading conditions.
Less Flexibility in System Expansion: Adding more panels to a system with a string inverter can be more complex. It often requires ensuring that the new panels are compatible with the existing string configuration and inverter capacity.
Shorter Warranties: String inverters typically come with shorter warranties compared to microinverters. This can be a consideration for long-term reliability and replacement costs.
Less Detailed Monitoring: String inverters usually offer system-level monitoring rather than the more detailed, panel-level monitoring provided by microinverters. This can make it harder to identify specific issues or inefficiencies in the system.
When choosing between microinverters and string inverters, it’s essential to weigh these downsides against your specific needs, including installation size, budget, shading conditions, and maintenance preferences.
Conclusion
Microinverters and string inverters are two types of technologies used in solar panel systems to convert the direct current (DC) electricity generated by solar panels into alternating current (AC) electricity that can be used in homes and businesses or fed into the electrical grid. Each has its own advantages and disadvantages.
In conclusion, micro-inverters can be better in scenarios with shading issues, for smaller or phased installations, and when detailed monitoring is desired.
However, string inverters might be more suitable for larger, unshaded installations where cost is a significant factor.
Your specific situation and priorities (cost, flexibility, monitoring needs, etc.) will determine the best choice for your solar energy system.
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