Inverters are an essential part of any solar panel system – they convert direct current (DC) electricity produced by your solar panels into usable alternating current (AC) electricity. There are a few different types of inverter technologies to consider. String inverters are a tried-and-true inverter technology, and one of the oldest options available in the market today.
What are string inverters? How do they work?
A string inverter system connects groups of solar panels in your system by “strings”. Each string connects to a single inverter where electricity is converted from DC to AC electricity. This single inverter is typically located in an electronics box that’s placed on the side of your house or in your garage. Because panels are connected in strings to the inverter, if one or more panels is underproducing energy (due to shading, dirt, or some other factor), the panels on that string will only be able to produce as much electricity as the affected panel.
A string inverter is typically capable of handling multiple strings of panels attached to it. For example, you may have three strings of five panels each, for a total of fifteen panels on a single string. The size of the string inverter in kilowatts (kW) and the wattage of the solar panels you use will determine how many panels you can string to one inverter without wasting energy. To learn more about solar inverter sizing, check out our blog on the topic.
When to use string inverters with a solar panel system
String inverters are effective for many solar installations, but in some cases may not be the most suitable solution. Because a string of panels can each only produce as much energy as the lowest-performing panel located on that string, this technology is not best for solar installations that experience shading. If you have tall trees or other objects near your solar installation that will shade parts of the system during the day, consider module-level inverter systems like power optimizers or microinverters. Alternatively, you can remove trees and other obstructions.
Additionally, if your solar panels will be facing different directions, a string inverter may not be the best choice. While south-facing panels will be able to produce optimal levels of electricity, panels facing different directions or at different tilts may produce varying amounts of electricity at the same point in time, limiting the overall production of your solar panel system.
How to evaluate string inverters
When comparing string inverter options, there are a couple of main metrics to keep in mind:
Just like solar panels, string inverters have varying efficiencies. An inverter’s efficiency is a measure of how much energy is lost in the form of heat during the conversion from DC to AC electricity. Higher efficiency string inverters lead to higher overall system efficiencies and more solar electricity production.
Solar inverter sizing depends on a number of factors including the size of your solar array, your geographical location, and other site-specific considerations. Larger string inverters will generally be more expensive but may be worth it to maximize energy production.
Most string inverters come with a product warranty between 5 and 15 years which covers problems like manufacturer defects and environmental damage to your inverter system.
Although they are not typically the most expensive component of a solar panel installation, it’s still important to weigh the price you’ll pay for a string inverter. Larger, more efficient string inverters with longer warranties often come with higher price tags, but depending on your roof setup and geography, you may not need to spend the extra money upfront.
String inverter manufacturers
Many manufacturers have string inverter products available. Here are a few of the biggest names in the category:
Based in Austria, Fronius makes both residential and commercial string inverter systems. They offer three main lines of products: the Fronius Primo, Fronius Symo, and Fronius Symo Advanced series.
SMA is a German company with residential and industrial solar inverter system offerings. They have main string inverter series (Sunny Highpower, Sunny Tripower, and Sunny Boy) for residential applications, and also offer larger central inverters and battery inverter products.
Another string inverter manufacturer option for residential and commercial rooftop solar energy systems is the China-based company Sungrow. According to their website, their string inverter solution has been installed for almost 70 gigawatts (GW) of solar worldwide as of mid-2018.
Solar energy systems help you save money wherever there’s sun
The best way to ensure that your string inverter system is sized and installed appropriately is to work with a qualified, reputable solar installer. You can sign up on the EnergySage Solar Marketplace to receive multiple quotes online from pre-screened, vetted installers. These EnergySage Approved installers will use design tools to make sure your solar array and inverter are set up accordingly given your electricity needs, solar equipment, property, and geography.