Description:

Description

Micro-Inverters vs String-Inverters

Let's start with the differences between a micro-inverter is and a string-inverter:

  • Micro Inverter - A small weatherproof inverter installed behind each solar module. Converts the DC power generated by the solar panel into AC power right at the panel. This is a new development in solar power.
  • String Inverter - Also called a central inverter. With these, solar panels are connected together into strings and the DC power is wired to a large inverter in a central location. It converts the power for all the modules at once. This has been the traditional approach over the last 40 years.

Advantages of Micro-Inverters over String-Inverters:

Simplicity

  1. Micro-Inverters can be installed safely and easily by a homeowner while string-inverters cannot.  This is the single most important advantage since it means you can save 50% or more  by doing it yourself.
  2. Micro-inverters are "plug & play" so installing them is about as complex as installing an air conditioner or a toaster.
  3. String inverters require running multiple strands of thick DC wires down from the solar panels through a conduit to the string inverter. Micro-inverters connect to a simple AC trunk table carry normal household voltage.
  4. String-inverters require the installer to work with 4-8 sets of high voltage DC wires that need to be correctly connected to the inverter.  This puts it beyond the abilities of the typical homeowner. 
  5. String-inverters require the installer to calculate the line loss ohms to size the wire for the runs from the panels. They also  require the installer to run a separate grounding system for the panels, racking and string inverters. 
  6. String-inverters require the installer to design the system to load balance each string of panels for even loading of the inverter. 
  7. If a single panel malfunctions in a string inverter system you will have trouble determining which string and it will be impossible to determine which panel in a string without removing all of them and testing them one at a time with a micrometer.

Efficency

  1. Micro-inverters optimize the power output of each individual panel resulting in 15% more power per panel.
  2. If there is any shading then string inverter systems will operate poorly but a microinverter system will operate optimally. 
  3. If a single panel malfunctions in a micro-inverter system then you will know immediately which one and it will not affect the rest of the system. 

Safety

  1. String-inverters expose the installer to hundreds of volts of dangerious DC power while micro-inverters do not.
  2. Micro-inverters do not generate power when not connected to your home power grid. Therefore they are safe to handle, even in full sun. Panels connected to a string inverter generate power as soon as exposed to light so need to be handled carefully.
  3. There are dozens of ways that the homeowner can incorrectly wire a string inverter and either burn it out, damage the panels or kill themselves. Any damage caused is not covered by warranty. 
  4. There are zero ways to incorrectly wire a microinverter because it is "plug & play". Every connection is idiot proof and cannot be touched and cannot be incorrectly connected.

Longevity = Cost Effectiveness

  1. Micro-inverters carry a 25yr warranty and have a average lifespan of 332 years(Yes that's right).  String-inverters have a 10yr warranty and don't last much longer due to their design.
  2. The most expensive price of equipment, the string inverter, will most likely need to be repurchased twice more during the life of a system. In the case of your size system this is a $6000 expense every 10-12 years. This adds 50% to the cost of your system hardware over it's lifetime.
  3. The most complex part of an installation, wiring the string inverter, must be redone every 10-12 years and each time you can count on the inverter being designed differently so it must all be relearned each time. If a pro does this he will charge 4-5k each time.