Deciding Between String Inverters or Microinverters

Micro vs. String Inverters

When developing a solar panel system, one of the biggest decisions is: String Inverters or Microinverters?

Inverters are the workhorses of your array. Their basic (yet very technical) job is to convert the solar panel’s direct current (DC) electricity into usabe alternating current (AC). This is what your residential solar panel system is built on and the type that can be fed into the utility grid (read as “sold back to reduce your electric costs”).

Inverters are probably the second most important component of your system after the panels themselves.

String Inverters / Centralized Inverters

string inverters on a commercial solar installation
String Inverters on a commercial solar installation

String inverters have been around a long time, thus giving them the status of the most common type in the inverter industry. Their history and global influence mean that the cost is lower than microinverters. A string is an array of 4+ panels connected in parallel to each other and then terminating at the inverter. They are typically installed at ground level near the circuit panel.

The downside to string inverters is that if one panel is partially shaded it can lower the production of the whole string. Also, if you have multiple planes on your roof, the array will lower production to the lowest producer in the string.

Imagine when your water hose gets a kink in the line. It doesn’t matter where, the flow out of the end is degraded.  Your whole array will be generating less power possibly because of one solar module’s potential.

Pros and Cons of String Inverters:

+ The technology is more established
+ Lower cost
– Weaker warranty
– Production limited to the weakest panel

Microinverters

solar microinverter on a rail system
Microinverters mounted on a rail system.

What is the main alternative to the string inverter? Enter the microinverter. They have been around a while, but haven’t had the market share that string inverters have held as they drove up the cost per watt, and in the power generation industry consumers are a bit more risk-averse.

Pros and Cons of Microinverters:

+ Array production not decreased by the weakest link
+ Easy to expand the pv system
+ More efficient conversion
+ Monitoring of each panel via browser/apps
– More expensive

What makes microinverters more appealing than string inverters?

Microinverters’ biggest advantage lies in the fact that each panel’s current is being converted at the source. These are either mounted on the racking system next to the panel, or integrated into the panel itself (in some newer models).  This means that you effectively have as many “water hoses” as panels.  

If one module’s production decreases from shade, angle, or failure, the rest of the production is maintained at peak production.  This is more likely to happen in residential pv systems as houses face many directions with many roof angles.

In addition to localized electric conversion, microinverters are more modular which allows for easier expansion of the entire array.  The solar panel installers can theoretically add more panels as your electric demand increases.

Microinverters also allow you to monitor the production of each individual panel. This makes it very handy in troubleshooting failure or weak production in your array.  

The monitoring is relayed to the home/business owner via a web portal or smartphone app.  For the geekier solar owners, this also allows you to “micro” manage your energy production down to a finer scale.  

Warning:  Monitoring your individual panels can lead to a dangerous time suck as you watch every minute of the sun passing over your system and how it affects your production.

A few extra bonuses in regards to microinverters:

  • This type of electric inverter dissipates much less heat, so there is no need for active cooling.  This equates to noise reduction and fewer components to fail.
  • The warranties on microinverters are usually better than String inverters.
  • Microinverters are more efficient than string inverters, giving them a little more power production.
  • When choosing an inverter, make sure to take note of ANY shade on your roof.

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