What’s the Difference Between a Micro Inverter and a String Inverter?

Micro inverters vs string inverters is a question that will ultimately come up at some point during the design process of your solar PV system.  Before we can discuss the pros and cons of micro inverters and string inverters, it is important to understand what an inverter actually does; Inverters convert the Direct Current (DC) produced by solar modules into Alternating Current (AC) for your home or business (often referred to in the industry as “usable electricity”).
Modern inverters are much more sophisticated than they use to be, offering a plethora of software that can help to monitor and track efficiency as well as remotely troubleshoot any future concerns. For example, Maximum Point Power Tracking (MPPT) is a modern software development used to deliver the maximum amount of power available throughout your solar pv system – This is important, since each solar panel can produce different amounts of power due to manufacturing anomalies, intermittent shading, leaves, dirt, passing clouds, and/or other factors

Design of Micro inverters vs String Inverters

A string inverter (also known as a standard or central inverter) is a standalone box that is generally mounted next to the service panel. They can vary in size but are comparable to a desktop computer.
Micro inverters are much smaller in size (approximately the size of a paperback book) and are mounted directly underneath each solar module.
 

 Performance of Micro Inverters vs String Inverters

String Inverters – The entire solar PV system is connected to a single inverter (or sometimes separated into a second inverter). A string inverter treats the system as a single series circuit – capping the electricity production of each panel by the lowest producing panel in that ‘string’ (as seen in the illustration below). Modern string inverters have mitigated a majority of these issues by way of PV optimizers, which lesson the effects of shade on panels and create many of the same features of a micro inverter, allowing the end user to monitor individual panels.
String inverters are rated for a specific amount of electricity and sized for the solar PV system that it will be used on. If your system ever needs expanding, a new inverter my be required to handle the extra capacity (or can be planned ahead by over-sizing the inverter.)
Micro Inverters –  Each solar PV module receives its own inverter, forming a parallel circuit, and can be isolated individually in order to take full advantage of the production of each individual panel.  Micro inverter are designed as a “plug-and-play one size fits all” which means there are less parts to them, but they are not as customize-able and, therefore, do not offer as many features. Because each panel receives its own inverter, there are many more parts required for the system to work and, therefore, more potential points of failure that can occur. Keep in mind: if a micro inverter needs to be replaced, the panel, racking, and inverter need to be removed in order to be reached and roof access will be necessary. On the other hand, micro inverters  are easily expandable be simply adding additional micro inverters with each panel.

 

Warranties & Cost of Micro Inverters vs String Inverters

The cost and warranty of the inverter is usually a large factor for most individuals when deciding what kind of inverter to go with. String inverters tend to be more economical in price but carry a shorter warranty, typically 10 years, where as a micro inverter will typically carry a 25 year warranty, and carries a greater cost due to the quantity of inverters needed for your solar PV system (depending on the size of the array.)
It is worth noting that string inverters have been on the market for a longer period of time and therefore have more data and analysis on them than micro inverters; The warranty period is not necessarily a measurement of the quality of the product, but rather how long the company is willing to take ownership of the product. That is to say, as with any product, the inverter may last well beyond the warranty period without any trouble or it could have problems immediately (reputable solar installation companies will have done their research and only use top quality products.)

Features and User Interface of Micro Inverters vs String Inverters

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[/one_third] [two_third_last] Additional features and user interfaces (UI) for micro inverters vs string inverters differ drastically, even within the same class of inverter.
When it comes to UI, it is a matter of preference. Research the software, viewing snapshots and reading customer testimonials, and ask your solar PV professional for recommendations and assistance.
While most modern string and micro inverters feature the option of wireless monitoring, string inverters can include several other customized features such as: dedicated outlets (if the grid has an interruption, a single outlet can continue to be used drawing power form the inverter), weatherproofing (for outdoor mounting), digital displays, and many more options.

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Off Grid Capabilities of Micro Inverters vs String Inverters

This one is straight forward. If you are building an off grid solar PV system or want to have the ability to go off grid or add batteries in the future, you need a string inverter; currently there are no micro inverters on the market that allow for off grid capabilities. This is due to the way a micro inverter works – micro inverters are always searching for a 240V AC reference source (the grid) and are designed to shut down if it isn’t present simulating a line worker switching off the mains for maintenance, for example.

Conclusions on Micro Inverters vs String Inverters

As you can see, there are pros and cons for both micro inverters and string inverters. It is important to communicate with your solar installer and let them know what is important to you – whether it is cost, warranties, monitoring, versatility, or all the bells and whistles. Other factors that can play a role in determining the best inverter for your system are potential shading, system size, and current location of your utility meter.
To learn more about inverters and the top-quality products Osceola Energy offers, contacts us today! We offer free quotes and leading class design and installation all at quality pricing to fit your budget