types of solar inverters

String inverters vs. power optimizers vs. microinverters: what you need to know

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As you consider a solar panel system for your home, one of the key decisions you need to make is the type of inverter to install. Inverters convert direct current (DC) electricity generated by your solar panels into usable alternating current (AC) electricity. Given the complex power electronics and software contained within, inverters are vital to the ongoing performance of your solar power system.


string vs. power optimizers vs. microinverters

Breaking down solar panel inverter technologies: string inverters, power optimizers, and microinverters

There are three types of inverters that are currently available to you for your solar energy system: string inverters, power optimizer systems (also known as string inverters + power optimizers), and microinverters. Power optimizers and microinverters are often collectively referred to as “Module-Level Power Electronics” or MLPEs.

String inverters are by far the most commonly deployed inverter option globally, and make up the vast majority of the world’s inverter market. However, MLPE technologies have gained in market share over the last five years as their costs have come down.

Key takeaways: string inverters, microinverters & power optimizers


  • Inverters convert the DC electricity that your solar panels produce into appliance-friendly AC electricity.
  • The three main inverter options available for residential and commercial solar installations are string inverters, microinverters and power optimizer systems.
  • String inverters are the most commonly installed worldwide.
  • Microinverters and power optimizer systems are typically more expensive than string inverters.
  • MLPEs allow you to monitor the power production of each individual panel.

String inverters

string inverter

String inverters are the most cost-effective inverter option available in the U.S. Traditionally, a solar installation company would propose a string inverter for your system if your roof had limited shading throughout the day and did not face in multiple directions (such as a gabled roof). However, thanks to recent hardware and software updates from the major string inverter companies, string inverters are now applicable in a wider set of circumstances.

How string inverters work

Your solar panels are arranged into groups connected by “strings” (hence their name!) You can connect multiple strings of panels to a single, centralized inverter, which transforms the DC electricity produced by the panels into usable AC electricity for your home or business.

Solar companies have used string inverter technology for decades. It’s a super reliable, tried-and-true technology, but as with your other inverter technology options, may not be suitable for certain types of installations. Although modern solar inverter and panel technology allows individual panels to continue producing power even if a part of the panel is shaded, without module level power electronics, string inverters can only optimize power output at the string level, not at the individual panel level. This means string inverter systems aren’t always the best solution for homes that are prone to shading throughout the day. However, their ease of install and lower price point make them attractive to many homeowners and installers.

One of the most common reasons for individual solar panels to produce less power–or stop producing power altogether–is shade from nearby objects. If your roof experiences shade throughout the day or in certain seasons, you could either remove the source of the shade (e.g. cut down a tree) or install the panels in a sunnier space (e.g. ground mount or carport installation).

Compare your inverter options


EnergySage’s database of solar reviews has comprehensive information about specific installers, financiers, and equipment manufacturers, including manufacturers of string inverters, microinverters, and power optimizers. If you are looking for a review of MLPE technologies, EnergySage has also developed a comprehensive comparison of micro-inverter and power optimizer options.

String + power optimizers

power optimizers

Power optimizer systems offer many of the same benefits as microinverters, and are often considered a compromise between microinverters and the standard string inverter.

How power optimizer systems work

Like microinverters, systems with power optimizers have an individual optimizer component located at each panel. However, instead of converting the DC electricity to AC electricity right at the panel site, they “condition” the DC electricity and send it to a string inverter for conversion. If your roof experiences shade during the day, the panel level optimization afforded by power optimizers often results in higher system efficiency than using a string inverter alone.

Similar to microinverters, power optimizers not only reduce the impact of panel shading on system performance, but also offer panel-level performance monitoring. 

Microinverters

microinverters

Microinverters, another form of MLPEs, are rapidly gaining in popularity, particularly for residential solar panel systems. 

How microinverters work

Systems with microinverters typically have an individual installed on the back of each solar panel. They convert the DC electricity from your solar panels into AC electricity on your roof, with no need for a separate string inverter. In most cases, installers mount the microinverters onto the back of the solar panel itself, but they can also be placed next to the panel on your solar racking system.

Microinverters take MLPE to the logical conclusion: while power optimizers aggregate the electricity from your panels and send it to a string inverter for the DC to AC conversion, microinverters make the DC to AC inversion right at each individual solar panel. As a result, like with power optimizer systems, microinverters also allow you to monitor the performance of individual solar panels.

How “smart modules” use microinverters and power optimizers


How “smart modules” use micro-inverters and power optimizersMany microinverter and power optimizer companies are partnering with solar panel manufacturers to create “smart modules.” Simply put, a smart module is a solar panel with a piece of MLPE equipment already integrated into it. This simplifies installation and cuts down on labor costs for installers. Many of the world’s biggest panel manufacturers now have smart module options available, including LG, Panasonic, and SunPower.

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About Kerry Thoubboron

Kerry has worked in solar for more than 6 years, starting her career as an Energy Advisor dedicated to helping customers compare their options and make well-informed solar decisions. She graduated from Boston University with a degree in Environmental Analysis and Policy. Outside of work, you can find Kerry snowboarding, watching The Office, or having passionate debates about which New England state is best (spoiler: it's Vermont).

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