• Marlena

How to know you're choosing the right Inverter

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 part of your solar power system.

Types of Inverters

There are three types of inverters that are currently available to you for your solar system: string inverters, power optimizers (also known as string inverters + power optimizers), and micro inverters. In this article, we’ll discuss the differences between these three as well as the pros and cons of micro inverters vs power optimizers. Before we get into the pros and cons, let’s look at the functionality of the different inverters.

Solar Inverter

String Inverter

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, you might need to look into micro inverters or power optimizers.

Micro Inverter

Micro inverters are installed on each individual panel in a solar 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. The biggest advantage 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.

Power Optimizers

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.

Which Option is the Best?

The age old argument is that micro inverters perform more efficiently and that they are safer. On the down side they are more expensive. Most micro inverters cost at least $150, whereas optimizers only cost about $70.

Micro Inverters vs. Optimizers

A micro inverter converts the power of the panel from DC to AC right in the panel which increases efficiency and safety. One of the cons of micro inverters is not only are they very expensive, but also the fact that using them creates more components in the system. This means there is a higher risk of having an issue with the system. If there is a problem with micro inverters, the installer has to physically get on the roof, locate the panel with the problem, unscrew the panel and replace it. Changing over a micro inverter is a much more difficult task than replacing a string inverter.

Let’s say half of your system is shaded throughout the day. If you just have a string inverter, your whole system stops working. You can prevent this from happening by putting optimizers on the back of the panels or purchasing micro inverters.

Not only are string inverters and optimizers together less expensive than micro inverters, the major disadvantage of a micro inverter is that you need to purchase a control unit (nvoy). This is usually at least $900 on top of the micro inverters. This is why we generally recommend to our customers to purchase a string inverter plus power optimizers if there is a risk of partial shading.