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Central Inverter vs. Microinverters: The Pros and Cons

So you’re installing a photovoltaic (PV) system.  Do you go with microinverters or stick with a central inverter?

What does an inverter do?

The task of an inverter is to convert the direct current (DC) electricity produced by your solar panels into alternating current (AC), which is needed for the overwhelming majority of electrical devices.  The AC power that isn’t used by your home is back-fed into the utility grid, hence the term “grid-tied.”Click here to learn about the basic components of a PV system.

Microinverters

Microinverters convert the DC electricity from each panel into usable, grid-quality AC electricity.   They attach behind individual solar panels in the array, allowing each module to operate independently instead of optimizing for the “weakest link.”  Turning the solar panels’ DC electricity into AC at a modular level means there is no single point of failure and you’re maximizing the potential output of your system.

Because of this, microinverters are particularly advantageous for systems in locations that have shading or some potential coverage (i.e. dirt, snow, chimneys, etc).

Microinverters also use a technology called Maximum Power Point Tracking (MPPT), which optimizes the electricity output by responding to the varying levels of light every couple of minutes.

In addition to maximizing the yield of your system, micoinverters’ easy design, installation, and scalability have made them popular for residential applications.   Besides getting up on a roof and pulling a permitting, adding to your existing system with microinverters  like the Enphase M215 microinverter should be little trouble.

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Each microinverter has its own IP address so it can be monitored remotely with web-based software.  Microinverters also allow for module level monitoring and comprehensive analytics, making it possible for you to view how much energy is being produced by each solar panel.

The main disadvantage of microinverters is the price tag- they still cost more per Watt than central inverters.  Critics of microinverters have also made note that these sensitive electronics can exposed to elevated temperatures on the roof and there is lack of field data to go along with their 25-year warranty.

Enphase Energy currently dominates the microinverter market and has been increasingly popular for residential applications, particularly in California.   Enphase offers a twenty-five year limited warranty on their microinverters.

Microinverters are recommended for residential and DIY solar applications, especially if there are shading concerns or there’s a chance of expanding the system in the future.

Pros:

• Easy design, installation, & scalability

• Maximum Power Point Tracking (MPPT)

• Optimized for shading

• Remote monitoring capability

Cons:

• Less of field data

• More expensive

• Relatively new technology

Central Inverter

Traditionally, central inverters have been used in solar systems to convert DC to AC.  Multiple solar panels connected to one location, these string inverters are the most common choice for residential solar applications.

Central inverters have been around longer and thus acquired more field data than microinverters.   This collective real-world use gives central inverters a certain kind of credibility and people naturally feel more inclined to place their trust in a proven technology.

 The key benefit of a central inverter is cost.  The bottom line is that central inverters currently cost less per watt than microinverters.  This is why many home owners and most utility scale industrial applications opt for central inverters.  A good number of people argue that having a single conversion point simplifies grid management for such large applications.

Critics of central inverters point out that high voltage levels are centralized and pose a safety hazard.  Fire hazard and electrocution risk is higher when you have string-based systems with no built-in power control within the array.

The main disadvantage of having a central inverter is that your system is “only as strong as its weakest link.”  If one panel is subject to shading or some other form of coverage, some critics argue that the energy output of your array can be decreased by up to fifty percent.

String inverters are recommended for larger photovoltaic systems with no shading concerns, ground-mounted systems, and non-residential applications.

Pros:

• Proven Technology

• Predictable

• Cost-effective

Cons:

• Not optimized for shading

• Difficult to expand

• No monitoring

• High Voltage

Which is better: a central inverter or microinverters?

Right now there is a place for both central and micoinveters, each with their respective applications.   If you have any questions, call us at (866) 798-4435.

If you were putting a solar system together, would you choose microinverters or a central inverter?

Author: Tom Jackson

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