Fundamental Concepts of String Inverters and Micro-Inverters


With all the new solar technologies out there and not much straight forward information, it is sometimes difficult for homeowners to make the right decision on an adequate solar system for their home. Our goal is to break down all the technology and information necessary to make the transition to solar a whole lot easier for you. Today we are going to simplify the difference between String Inverters and Micro-Inverters as well as explain the pros and cons of each.

What String Inverter and Micro-Inverters Really Are

Both string inverters and micro-inverters convert the DC electricity generated by the solar panels into AC electricity that can be utilized inside a home. String inverters are also known as central inverters since they are responsible for converting AC electricity from a group of panels. Micro-inverters are connected to only one solar panel and act as individual systems while converting DC electricity to AC electricity and are sometimes referred to as “module-Level Power Electronics” or MLPE’s. Currently string inverters are by far the most common inverter being deployed for solar systems because of their relatively low cost, however, MLPEs are gaining attention and popularity because their costs have decreased in recent years. According to GTM Research, over half of all residential solar systems installed in the US in 2014 used MLPE technologies. Micro-inverters are preferred for installations where one or more panels may be under shade or where not all panels are facing the same direction.

String Inverters

Most solar companies tend to offer these inverters to homeowners whose roofs do not experience any type of shading during the entire day and if all the panels will be facing the same way.

Solar panels are typically arranged into groups connected by “strings”. These groups of solar panels are referred to as a string of panels and they are connected to a single inverter. This single inverter converts DC electricity produced by the string of panels into appliance-friendly AC electricity. One of the bad things about a string of solar panels is that it can only produce as much electricity as its least efficient panel. In other words, the power output from the entire string would be reduced to the level of the least productive panel in the string. This is the reason why string inverters are not recommended for solar panels that have different directions or are exposed to some shading during the day.

Micro-Inverters

Micro inverters are particularity gaining attention in the residential sector because they have started to become cost-efficient like string inverters. The major advantage of Micro-inverters is that they cancel the negative impacts of partial or complete shading. Micro inverters are installed on every single solar panel in a solar system. They convert DC electricity to AC electricity for their corresponding panel without needing a central inverter. Sometimes micro inverters are mounted right next to their corresponding panel or in some cases they come integrated into the panel itself.

String Inverters- Pro

  • Often, offer a lower initial cost per peak watt price

  • Easier to install since only one is required for multiple panels. Also makes them easier to maintain, however, it could be possibly more difficult to troubleshoot.

String Inverters - Cons

  • Any problems with one panel are felt across the whole string. If one panel under shade and power generation decreases, then the rest of the panels suffer and equivalent output loss.

  • Large inverters can be bulky and take up space on the side of house.

Micro-Inverters – Pros

  • If one panel is under shade and power output is reduced, the rest of the panels are not affected and keep producing their own relative power.

  • Tend to be easier to repair because there is usually a single point-of-failure.

Micro-Inverters Cons

  • Higher cost than string inverter per peak watt, however, this is changing with new technology that accept DC input from two panels and other new advancements

  • Tend to be more complex and costly to install since must be mounted to every single panel


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