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Solar Microinverters Vs. Optimizers: Which Is Best?

Dec 16, 2022

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If you’re installing a solar power system, it’s helpful to select the best equipment. Although many people think about solar panels when selecting components, the inverter is also critical. What type of solar inverter your system has will impact how it performs under different conditions and how efficiently it charges solar batteries.

If your roof is partially shaded or it has a complex roofline, whether to use optimizers or microinverters is an especially important consideration. Likewise, if you are on a tight budget and want to get the most out of your solar investment, your inverter selection is an opportunity to reduce the cost of your array. Working with a reputable installation company can help ensure you get the most efficient system for your situation and budget.

Types Of Inverters For Home Solar Energy Systems

There are two types of electricity, direct current (DC) and alternating current (AC), and the terms describe the direction electricity flows in a circuit. Whereas DC power flows in a single direction, AC power periodically changes direction, flowing both back and forth.

Although solar panels generate DC power, our homes mostly use AC electricity. Thus, solar inverters convert DC electricity produced by photovoltaic (PV) panels into AC electricity that homes can use. Solar shoppers have two types of inverters to choose from: string inverters and microinverters.

Inverter options:

  1. A string inverter without power optimizers
  2. A string inverter with power optimizers
  3. Microinverters

With string inverters, also known as center inverters, one unit converts the electricity for multiple solar panels. This is an older type of inverter and was the only option until a newer type of inverter hit the market. String inverters can work alone or with DC power optimizers.

Microinverters are a newer inverter option for PV systems with added features and benefits. They are mounted on the underside of solar panels and convert the current for the output from just one module. Microinverters often have a longer warranty than many string inverters, but they usually can cost more.

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How Solar Module-Level Power Electronics Improve Photovoltaic Systems

One of the goals when designing a solar PV system is boosting solar energy production – and one of the biggest obstacles is shading. Module-level power electronics (MLPE) can help mitigate the impact of shading. MLPEs include microinverters and DC power optimizers which connect to each solar panel in an array to help improve the system’s total electricity production.

MLPEs improve the maximum power point tracking (MPPT) of individual solar panels. MPPT is essential for optimizing the relationship between your solar panels and the battery bank or electric grid. Thus, it boosts energy extraction under various conditions by keeping the system operating in the ideal operating voltage range.

If a solar system has a string inverter and no MLPEs, shading on one panel can have a disproportionately large impact on overall energy production of the photovoltaic array. Just a little shade on one module from a chimney or dormer can cause the total system output to plummet.

In addition, if solar panels have a different orientation, like if they are mounted on roofs with different angles or azimuths, solar production decreases without MLPEs. However, power optimizers and microinverters allow each panel to function at its maximum power point, largely overcoming shading and orientation mismatch issues.

In addition, solar systems without MLPEs don’t have panel-level monitoring. This means that your system monitoring data will only show what the whole system is doing and not each individual panel. However, if your solar system has microinverters or power optimizers, you should be able to see how each panel is performing. This is especially helpful when troubleshooting issues.

Another benefit of MLPEs is that they provide rapid shutdown capabilities for solar energy systems. The National Electric Code (NEC) requires solar systems be able to deenergize to avoid electrical hazards, and microinverters and DC power optimizers fulfill this requirement. Firefighters or other first responders may need to safely access the roof and an operational PV system could create issues.

Power Optimizers Pair With String Inverters

Solar contractors can install DC optimizers on each solar panel and pair it with a central inverter to boost the performance of the system. They provide MPPT abilities for each solar panel, increasing total system output. Let’s look at the pros and cons of a power optimizer paired with a central inverter.

Pros

●      Enables module-level data production for your solar monitoring system

●      Helps prevent system-wide power loss from a single low-producing panel

●      Reduces the impact of partial shading on an array by 20% to 35%, according to the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy

●      Resolves production issues from orientation mismatch which often result when solar panels are installed on different roof planes

●      Power optimizers work efficiently with backup battery, which may require a hybrid inverter

●      Helps solar systems comply with rapid shutdown requirements required by the NEC

●      Optimizers commonly have a 25-year warranty

Cons

●      Unlike with microinverters, adding more panels to the solar array may potentially require a new central inverter

●      Although both microinverters and power optimizers commonly have 25-year warranties, the central inverter that is paired with the optimizers may have a shorter warranty. However, some inverter manufacturers may allow customers to extend the warranty to 20 or 25 years for an additional fee.

●      Power optimizers are more expensive than just a string inverter with no power optimizers, but the added expense might be cost-effective due to the increased energy output, especially if your roof is partially shaded or has complex rooflines

●      If a DC optimizer fails and needs to be replaced, an installer needs to go up on the roof to perform the repair

●      Power optimizers rely on string inverters and if they fail, the entire system can stop working

Microinverters Are A Flexible Option

Microinverters eliminate the need for a central inverter and are mounted on the back side of each solar panel. Although Enphase is a very popular microinverter manufacturer, there are now many microinverters available on the residential solar market.

Pros:

●      Like power optimizers, microinverters overcome orientation mismatch issues and mitigate the impacts of shading on electricity production

●      Microinverters give homeowners the ability to expand the size of their solar array without potentially needing to replace the string inverter

●      Panel-level monitoring enables easy troubleshooting and a better understanding of how each PV panel is functioning

●      Rapid shutdown function meets NEC requirements

●      If a microinverter fails, just that one solar panel is impacted

Cons:

●      Microinverters are more expensive than using a string inverter with no optimizers

●      Adding energy storage to a solar panel system with microinverters creates inefficiencies because both the solar panels and batteries operate with DC voltage. A microinverter will convert the energy to AC then back to DC in installations with storage.

●      If a microinverter fails, a renewable energy contractor needs to go on the roof to replace one

FAQs: Power Optimizers And Microinverters

Many solar shoppers have questions related to DC optimizers and microinverters.

Should I get microinverters if I’m considering a solar battery?

You can pair microinverters with a solar battery, but it isn’t the most efficient way to design your system. Since batteries operate with DC voltage and solar panels produce it, the most efficient design is to charge the batteries without converting the voltage from DC to AC and then back to DC again. Therefore, using a string inverter with power optimizers results in greater efficiency. Your solar installer will help you determine the best set up for your situation.

Are power optimizers or microinverters better if I might add more solar panels in the future?

If you add more solar panels and you have a string inverter, you might need to replace the inverter. Unfortunately, the capacity of the string inverter might not be sufficient for the additional capacity. However, if you know when you install the array that you might want to expand it, you can oversize the inverter to allow for the expansion. Otherwise, microinverters would be preferable because it will be cheaper to expand your solar panel system in the future.

The Bottom Line: Choose Microinverters Or Optimizers Based On Your System’s Needs

MLPEs have helped boost system output by mitigating issues caused by partial shading and solar system mismatch losses. Although there are some advantages and disadvantages to optimizers and microinverters, which technology is preferable depends on your needs and preferences. A quality solar installation company can help you determine which is best for your home taking into account your renewable energy goals and budget.

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