Inverters for Solar Systems Explained
When you’re considering solar 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. Next to solar panels, inverters are the most important equipment in your solar power system.
String Inverters Explained
String inverters can seem to be the least expensive option, but it is also the least efficient inverter technology on the market. With a string inverter, 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 AC electricity which is usable in homes.
The inverter also needs to be optimized within a narrow voltage range called the maximum power point (MPP) range. However, falling within the operating range just means the inverter is working — it doesn’t guarantee you’re getting the most power you possibly can out of a string inverter.
String inverters are an older technology that has been used for many decades but is not suitable for certain types of installations. The most glaring issue involving string inverters is the fact that if a string inverter fails all the panels connected to that string inverter stops producing electricity. Because string inverters don’t have individual panel monitoring you may not even be aware that a string inverter has failed.
In some string inverter installations Power Optimizers are installed on each solar panel to “condition” the DC energy and send it to a central inverter that finishes the conversion process. But you are still left with a single point of failure if a string inverter fails.
Microinverters 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 MicroInverters 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 MicroInverters 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.
Another advantage of MicroInverters is that since they are mounted behind the solar panels, the homeowner avoids mounting a large string inverter box to the side of their home. Also in the case of a failure it is very easy for a solar technician to replace a MicroInverters.
String inverters come with warranties of about 10 years and Microinverters come with 25-year warranties that match your solar panel warranty. That means your entire system is warrantied for the whole 25 years!
Which inverter is right for me?
While most solar companies still offer the older string inverter technology to their customers, more and more homeowners are opting for MicroInverters to take advantage of their vastly improved efficiency, reliability, and a more significant improvement to the resale value of their home.
String inverters do not have individual panel monitoring where MicroInverters have extensive monitoring capabilities.
The example image below shows a large solar array and each blue rectangle represents an individual solar panel. Not only is the individual panel output shown but also the overall output for day, week, month, and lifetime.