Solar Inverters

There are many solar inverters available - how do you know which one is best for you? Some important aspects to consider when selecting a solar inverter include wattage, efficiency, and warranty. All of these aspects plus more are considered in each solar inverters’ quality rating.

Solar panels produce electricity through the “photovoltaic effect”, which is a physical and chemical process that occurs when sunlight strikes solar cells. The electricity generated during this process is direct current (DC) electricity. However, most appliances run on alternating current (AC) electricity. A solar inverter’s main job is to convert the DC electricity generated by solar panels into usable AC electricity, making inverters vital to the success of your solar panel system.

There are three main types of inverter technologies available for your solar installation: string inverters, power optimizers, and microinverters. Both string inverters and power optimizer systems use a central inverter to convert the electricity from all of your panels from DC to AC, while microinverters convert DC electricity to AC electricity at each individual solar panel.

String inverters aggregate the output of groups of solar panels in a system into “strings”, which are then connected to a single, central inverter where electricity is converted from DC to AC electricity. With a string inverter, you can connect multiple “strings” of panels to the same central inverter, allowing some flexibility with your solar panel system design. However, string inverters do not provide panel-level optimization, which makes them less suitable for installs where you expect shading throughout the day or with complex roofs. String inverters are typically the least expensive inverter option, and are a great option for homes that receive consistent sunshine and with straightforward rooftops.

Power optimizers are located at each individual panel and are paired with a central inverter to complete the conversion from DC to AC electricity. Power optimizers don’t convert electricity to alternating current, rather, they “condition” the DC electricity to optimize its voltage before sending it to a string inverter to be converted. This results in a higher overall system efficiency compared to using string inverters alone in shading scenarios. In situations where you anticipate individual panels to experience a drop in production throughout the day due to shading or other factors, power optimizers can help reduce overall system inefficiencies.

Microinverters are also located at each panel site, but are not paired with a string inverter. Unlike power optimizer systems, microinverters convert electricity from DC to AC right at the panel. This approach also leads to optimized electricity production when compared to using a string inverter alone in shading scenarios or on complex roofs. By converting DC electricity to AC electricity right at each panel site, microinverters can also minimize the system-wide effects of a single panel under-performing.

Microinverters and power optimizers are often collectively referred to as Module-Level Power Electronics, or MLPEs for short. As a group, MLPEs offer several specific benefits when compared to traditional string inverters, including shade tolerance and individual panel monitoring options. However, MLPEs typically come with a higher price tag than string inverter options, so it’s worth comparing all of your options to see what is best for your specific solar installations.

The EnergySage classification system incorporates technical specifications for solar inverters to compare their performance, durability, warranty and overall quality. By assessing each product across a range of metrics, the EnergySage rating system groups equipment into five different classifications: Poor, Fair, Good, Very Good and Excellent.

Solar inverters rated as Poor or Fair are at the low end of what is currently available in the market, or may be outdated models no longer produced by manufacturers, and rarely stocked by solar installation companies. Equipment receiving Good, Very Good or Excellent ratings must meet a baseline set of criteria rigorously developed so that you can be confident that your solar energy system will meet your needs.