SOLAR INVERTER SELECTION CRITERIA, Central vs String Inverters (or Multiple Small Inverters)


Solar panels produce electricity as direct current (DC) and Inverters convert DC current to alternating current (AC) power that is used in our everyday devices or systems in businesses or at our homes.  Individual solar panels are connected in series to form strings.  When using a central inverter, the DC power produced from each string runs along wires to combiner boxes where they are connected in parallel with other strings.  From there, the DC power is then run into the central inverter and converted to AC power. When using string inverters, each and every string has its own inverter that converts the current to AC and let the power carry on its voyage. Here there is a list of various criteria whether to use a central inverter or multiple small inverters while deciding about our system design.





Central Inverter



String / Multiple Small Inverters



System Availability


Single failure results in loss of the whole or substantial amount of energy.

Single failure results in a small loss of output generated by the single unit.


Initial Cost





Installation Cost





DC Watt Unit Cost





Balance of System Cost





DC Wiring Complexity


High: Requires combiners, recombiners, and dc disconnects.

Low: Combiners and disconnects typically included with inverter.


AC Wiring Complexity


Low: Single AC Output

High: Requires AC collection system with panel board


Installation Weight


High: Requires heavy equipment, crane etc.

Low: Can be installed by two-man crews


Warranty Period


5 years: extensions available at added cost.

10 Years standard: extensions available at added cost.


Warranty Service


Onsite by trained technician

Replacement by installer


O&M Servicing


Whole system needs to be shut down for the service period.

Each string or array can be shut down for maintenance or servicing purposes.


Ongoing Maintenance


High ongoing maintenance cost because of cooling and air circulation.

Low ongoing maintenance cost. (No fans or air filters)


MPPT Accuracy


Single MPPT point for up to hundreds of strings.

Individual MPPT points for up to several strings.


Multiple Array Orientations


Not recommended

Individual Inverters (or MPPT input) for each array orientation.


Array Layout


Limited: all strings must be equal length

Each inverter can have different array configuration.


Multiple Solar Panel Types


Nor recommended

Different Solar Panel types can be used within a single system.


Subarray Fault Detection





Monitoring & Scada





Energy Yield



Typically 1% or 1.5% higher


Performance (comparison)


Requires additional data acquisition hardware and software

Easy to compare output and performance of multiple inverters


Interconnection flexibility


Must be ordered for a specific grid configuration.

Configurable for multiple grid configurations.




































































This Depar Solar Technical Article study can be used in your risk analysis / assessment for a feasibility study or can be a helpful piece of paper for your academic or business studies.
This article by Omer Muhtaroglu had been released on October 2013 (updated March 2017)











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