Comparative Analyses Between DC Power Optimizers & Microinverters

Last Updated on: 7th March 2025, 12:11 am

As a continuation to Types Of Power Converters In A PV System (yes, published 11 years ago), let’s discuss the power converters relevant to residential solar application. Aside from this power converter, one might need to consider available roof space, number of facets (which depend on the type of house), and the rated power from each solar panel when it comes to mounting solar panels at residential rooftops.

Usually, a cheaper and simpler way to convert the solar energy into usable electrical energy in most residential applications is via a string or a central inverter that converts the Direct Current (DC) solar power from a series of solar panels into Alternating Current (AC) power. If there is a failure in one of the panels or partial shading from the facets, the efficiency of the entire residential solar system could be lower — yielding less electricity production and further exacerbating the lifespan of the panel(s). If the panels are the split solar cells type, some of the above issues can be alleviated. However, there are still complications in manufacturing such split solar cells and the associated additional cost — making it little expensive over standard solar cells.

To get higher solar energy yield from the rooftop with minimum technical issues, Module Level Power Electronics (MLPE) optimize individual solar panels. Such MLEPs — DC power optimizers and microinverters — have become universal within the residential market. With respect to residential applications, microinverters have seen a high share of market domination against DC power optimizers. One significant advantage of MLPE over a string or a central inverter is that, if one MLPE fails, it does not affect the rest of the solar panel, whereas if a string inverter fails, the entire solar panel ceases to function and increases the downtime. In the following section, major similarities and differences between DC power optimizers and micronverters are discussed. 

Similarities 

• Efficiency: MLPE has excellent performance in challenging environmental conditions, in shaded areas, and in different orientations due to complex roof structure. Unlike DC optimizers, which require a string or a central inverter, microinverters independently convert DC to AC at module level, giving the microinverter higher efficiency than DC power optimizers in assessing the overall PV system efficiency.
• Shading condition: MLPE can overcome shading issues, making it resilient to panel degradation. MLPE optimizes the maximum power output from each panel: shaded and non-shaded. Whereas, in the case of a string or a central inverter, if one panel is shaded, it will lower the power production of the PV system and degrade the panel performance overtime.
• Power loss reduction: MLPE has Maximum Power Point Tracking (MPPT) algorithms that track the maximum power point for each panel irrespective of different orientation from complex roof structure. Whereas, in the case of a string or a central inverter, there will be mismatch in tracking maximum power points for each panel mounted in different orientation.
• Module monitoring: MLPE has real-time monitoring at the panel level in granular details. This allows the system to overcome any shading issues or technical faults, or even maloperation of the panel. Such monitoring helps to identify any faulty panel without requiring to inspect each panel, resulting in a more versatile system with reduced downtime.
• Rapid shutdown: MLPE has a rapid shutdown (as stipulated in NEC section 690.12) functionality which is an essential part of safety for PV systems on buildings or solar rooftops. Rapid shutdown helps to completely cut off the DC power from the panel in all eventualities, like natural disasters such as flood and fire. See examples from SolarEdge (DC power optimizers), Enphase (microinverters), and some challenges in PV systems without MLPE.

Differences 

• Cost: Cost per watt of microinverters is slightly higher than for DC power optimizers, by approximately 0.15 cents. This is primarily due to the requirement of individual power electronic inverters on each panel. Generally, DC power optimizers are more cost-effective, with lower initial investment and installation costs but with some extra upfront cost. Microinverters could be ideal for long-term investment considering the low service and maintenance cost.
• Reliability: Microinverters are an excellent choice in highly variable conditions such as environmental ones, complex roof structures, and different orientations. Given the lack of DC cabling set up in microinverters, the chances of failure due to high DC voltage is low. This makes micronverters’ failure rate lower, resulting in lower maintenance cost and improved downtime.
• Potential Induced Degradation (PID): PID occurs due to leakage current flowing from negative potential of the solar panel to the ground of the module metal frame, resulting in lower solar yield and eventually possibly causing solar module failure. DC power optimizers convert efficient DC to DC power via MPPT at module level keeping the DC voltage high. This makes the DC power optimizers likely to be exposed to failure due to PID. Whereas, a microinverter maintains voltage and restricts the total AC power at the module level, and for this reason, PV modules with microinverters are less likely to fail due to PID.
• DC arc-fault circuit protection: As stipulated in NEC section 690.11, residential application solar PV system DC circuits operating at 80 volts DC or greater between any conductors shall be protected by an arc-fault circuit interrupter. This safety measure is critical to avoid any fire-related eventualities from high DC arc-fault. Enphase microinverters are in compliance with this standard since their modules are operated below 80 volts DC. Whereas, DC power optimizers (SolarEdge, Tigo, & Huawei) have a function called safe DC mode which is not very specific to this standard but if coupled with their  string or central inverter it complies. 

The ideal choice between DC power optimizers and microinverters would depend on many factors, such as upfront cost, efficiency, reliability, low maintenance, and safety. In recent times, microinverter market share has risen in residential applications even though their cost per watt is slightly higher than DC power optimizers. Both MLPEs share significant advantages over a string or a central inverter, but microinverters are best suited in a difficult environment with complex roof structure where there is less compromise on safety and downtime.

Featured image from SolarEdge.

By Shiva Pukhrem