If you are considering a solar panel system 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. After the panels themselves, inverters are the most important equipment in your solar power system.
There are three types of inverters that are currently available to you for your solar energy system: string (also known as centralized) inverters, micro-inverters, and power optimizers. Micro-inverters and power optimizers are often collectively referred to as “Module-Level Power Electronics” or MLPEs.
String inverters are by far the most commonly deployed option globally and comprise the vast majority of the world’s inverter market. However, MLPE technologies are rapidly gaining popularity and market share as their costs have come down. Despite the global dominance of string inverters, GTM Research found that over half of all residential solar systems installed in the U.S. in early 2014 used MLPE technologies.
String inverters are the most cost-effective inverter option available in the U.S. Solar installation companies will generally offer you a system with a string inverter if your roof is not shaded at any point during the day and does not face in multiple directions (such as a gabled roof).
Your 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 appliance-friendly AC electricity.
String inverter technology has been used for decades. It is a tried-and-true technology, but is not suitable for certain types of installations. 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. For this reason, if your solar panels are installed facing different directions, a string inverter may not be a good choice.
One of the most common reasons for a panel to produce less power or stop producing power altogether is shading from nearby objects. If your roof is prone to shading any time during 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 where they will not be shaded.
Micro-inverters are rapidly gaining popularity, particularly for residential solar systems. Micro-inverters tend to be more expensive than string inverters or power optimizers, but their costs are falling as they become more popular.
Micro-inverters 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 micro-inverters 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 micro-inverters 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. Micro-inverters also allow you to monitor the performance of individual solar panels.
Find a complete list of micro-inverter manufacturers in our article about micro-inverter and power optimizer options.
Power optimizers offer many of the same benefits as micro-inverters, but tend to be slightly less expensive. Power optimizers are often considered a compromise between more expensive micro-inverters and the standard string inverter.
Like micro-inverters, 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 higher system efficiency than a string inverter alone.
Similar to micro-inverters, power optimizers reduce the impact of panel shading on system performance, and also offer panel performance monitoring. Systems that use optimizers are typically more affordable than those that use micro-inverters.
Increasingly, micro-inverter and power optimizer manufacturers 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 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 Trina Solar, ET Solar, ReneSola and SunPower.