Inverters for Solar Systems Explained: String inverters, microinverters, and power optimizers

March 29, 2019

When you are considering solar for your home, one of the key decisions you make is the type of inverter to install. Inverters convert direct current (DC) energy generated by your solar panels into usable alternating current (AC) energy. Next to the solar panels, inverters are the most important equipment in your solar power system.

String Inverters Explained

String inverters are the cheapest option, but also the least efficient inverter technology on the market. With a string inverter, solar panels are arranged into groups connected by “strings.” Each string of panels is connected to a single inverter, which transforms the DC electricity produced by the panels into AC electricity which is usable in homes.

String inverter technology has been used for many decades, but is not suitable for certain types of installations. The most glaring issue involving string inverters is the fact that if a single panel stops producing electricity, the entire system shuts down.

Another major flaw is that a string of solar panels will only produce as much electricity as its least productive panel – if one or more of your solar panels is shaded during any part of the day, the power output from that entire string would be reduced to its level. One of the most common reasons for a panel to produce less power or stop producing power altogether is shading from nearby objects such as elements of the roof or trees.

Microinverters Explained

Microinverters are installed on each individual panel in a solar energy system. They convert the DC electricity from your solar panels into AC electricity on your roof, with no need for a separate central inverter. In many cases the microinverters are integrated into the solar panel itself, but they may also be mounted next to the panel on the mounting system.

One of the major advantages of microinverters is that they cancel out the negative impacts of partial or complete shading. Because the DC-AC electricity conversion takes place at each panel, there is no “bottleneck” when one panel’s production decreases.

Another advantage of microinverters is that since they are mounted behind the solar panels, the homeowner avoids mounting a large string inverter box to the side of their home.

Power Optimizers Explained

Power Optimizers are seen as a way to make string inverters less inefficient. Like microinverters, power optimizers are located at each panel, usually integrated into the panels themselves. However, instead of converting the DC electricity to AC electricity at the panel site, they “condition” the DC electricity and send it to a string inverter. This approach results in slightly higher system efficiency than a string inverter alone.

Which inverter is right for me?

While most solar companies still offer the older string inverter technology to their customers, more and more homeowners are opting for microinverters to take advantage of their vastly improved efficiency, reliability, and a more significant improvement to the resale value of their home.