A solar string inverter converts all of the direct current generated by one or more solar arrays into alternating current that can be used to power the appliances at home. The number of solar arrays that can be connected to a string inverter depends upon the input voltage rating of the inverter.

A residential solar installation will have a single string inverter installed at homes near the electric meter. As each solar panel in the array is connected in series to the string inverter, an issue with any one panel in the string affects the energy generation of all the panels.

 String inverters are always combined with DC power optimizers to monitor the output power generated by each solar panel. They are placed on the back of each panel to modulate and enhance the voltage before being transferred to the string inverter, thereby avoiding the impact of shading.

Factors for selecting a solar string inverter

• Efficiency of String Inverter:  The efficiency of a string inverter is a measure of the amount of direct current being converted into alternating current. Higher efficiency implies that less power is wasted during the conversion. A string inverter efficiency of 98% means that 98% of the direct current fed to the inverter is converted to alternating current and only 2% of the input is wasted during the conversion.
• Power Rating of String Inverter: The power rating of a string inverter defines the amount of power the string inverter can handle. While designing a residential solar installation, it is desirable to choose a string inverter whose power rating is slightly higher than the amount of power the installed solar PV system is likely to produce.
• Number of Inputs: The input to the string inverter is the direct current that is fed from the solar PV array. Most of the string inverters have one or two inputs, but multiple-input inverters are also available. The choice between a single-input inverter or a multiple-input inverter is dependent on the size of the solar PV system.

Advantages of Using String Inverters

• Easy troubleshooting and maintenance
• Simple system design
• Cost efficiency is due to savings on upfront equipment costs

Disadvantages of Using String Inverters

• Do not have panel-level monitoring capabilities 
• Low reliability, as an issue with a single panel impacts the entire energy generation
• Has a shorter lifespan of 8 to 12 years
• Do not have rapid shutoff capabilities on their own
• Cannot be easily scaled up for higher energy requirements as system expansion would demand an inverter with a higher power rating

Click here to learn more about DC-AC Inverters.