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String Inverters, Micro Inverters and DC Optimizers

Which inverter system is right for me?

String Inverters, Micro Inverters and DC Optimizers

What's the difference between micro inverters, string inverters and DC Optimizers and which one is best for me?  Don't worry, its not as complicated as it may seem and we are here to help you throughout the process.  The answer to those questions depends heavily on your home's/business' location, architecture, and available space.  Each inverter system has its advantages and disadvantages so lets break them down individually.  

First, you might be wondering what is an inverter?  An inverter is what alters the current coming out of the solar panels from DC (direct current) to AC (alternating current) so it can be used readily in residential/commercial properties.  For simplicity's sake, an inverter is a metal box that you need in your solar array.

Micro Inverters

Micro inverters  are mounted beneath each solar panel on the roof and are approximately the size of a tablet/iPad.  Typically, one micro inverter is required for every one to two solar panels, depending on the micro inverter manufacturer.   With micro inverters the charge is inverted at the module level and brought into the property as AC.

Key Advantages: 

  • mounted on the roof out of sight
  • no space required inside the property
  • allow each module to operate independently, i.e shade on one solar panel will not hurt the entire array (or string within an array)
  • solar panels can be mounted on different faces at various angles without production loss
  • systems can be easily expanded over time

Micro inverters should be used when:

  • partial shading of the property occurs regularly (i.e. from a chimney, or tree)
  • system expansion is desired over time
  • solar panels are to be mounted on multiple incongruent faces
  • module level monitoring is desired

String Inverters

String inverters are significantly larger than their aptly named counterpart.  String inverters are roughly 3' tall x 1.5' wide x 1' deep or approximately the same size as a water cooler.  String inverters are typically mounted inside the property or in select cases can be mounted on the outside.  The major downside to string inverters is the if one solar panel is obstructed from sunlight, it negatively impacts the entire array (or string within the array).  

Key Advantages:

  • Most cost effective inverter system

String inverters should be used when:

  • solar modules are mounted at the same pitch/azimuth
  • there is sufficient space inside (or sometimes outside) the property
  • a large scale project is desired
  • an unobstructed ground-mounted solar array is desired

DC Optimizers

DC Optimizers are the string inverter manufacturer's answer to micro inverters.  DC Optimizers are an addition to the string inverter system which allow the modules to operate independently, similar to the effect of a micro inverter.  Optimizers are mounted on the roof beneath each module, however, a string inverter is still required.

As more strict electrical code stipulations come into play regarding module-level performance analysis (and rapid shutdown requirements), we predict that string inverter manufacturers will adapt by utilizing DC optimizers more frequently and more effectively.

Key Advantages:

  • allow each module to operate independently, i.e shade on one solar panel will not hurt the entire array (or string within an array)
  • solar panels can be mounted on different faces at various angles without production loss

DC Optimizers should be used when:

  • partial shading of the property occurs regularly (i.e. from a chimney, or tree)
  • solar panels are to be mounted on multiple incongruent faces
  • high efficiency is desired
  • module level monitoring is desired

The Cost

String inverters are the most cost effective, but are only applicable in select circumstances.  Because of string inverters' selectivity, micro inverters and DC optimizer systems are gaining in market share.  Both micro inverters and DC optimizers are fairly comparable in cost.  If there is no room in your home or building for a string inverter, then micro may be more applicable.  Similarly, if you are planning a large installation, DC optimizers' scalability may give them the edge.  Deciding a clear cut winner between optimizers and micro inverts is a difficult task and one that can only be evaluated as the technology develops and inevitable corporate feuds ensue.

Questions, comments or concerns? We would love to hear your thoughts on this.

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