How Should an Inverter Be Selected?

Inverter selection in solar power systems is extremely important — it is the heart of the plant.
A wrong choice or improper installation can cause serious losses.
Therefore, it is crucial to evaluate all details carefully before making a decision.

The following information may help you choose the right inverter.

Main Types of Inverters

There are three main types of inverters:

Central Inverter
String Inverter
Micro Inverter

(Note: An optimizer is not an inverter. It is a supporting device that enhances the power generation efficiency of solar panels.)

MPPT and System Balance

Inverters convert DC (direct current) from panels into AC (alternating current) and include components called MPPTs (Maximum Power Point Trackers) on the DC side.

MPPTs play a key role in maximizing panel efficiency and power output.
All strings connected to the same MPPT input must have equal conditions:

Panels must face the same direction
Installed at the same angle
Under similar climate and shading conditions

If these conditions differ, the weaker string can negatively affect the others in the parallel circuit.

That’s why the number of MPPTs is very important.
Ideally, one MPPT per string provides the best performance.
More MPPTs allow more flexible and efficient design — especially on complex or uneven roofs.

For ground-mounted systems, 3–4 MPPTs are usually sufficient.
For shadow-free, dual-sided roofs, 2 or more MPPTs work well.
For roofs with different directions or slopes, choose an inverter with multiple MPPTs.

Central Inverters

Advantages

Centralized configuration in a single cabinet or kiosk
Lower failure rate
Most cost-effective solution for large ground projects

Disadvantages

Few MPPT inputs, unsuitable for roofs
A fault may affect the entire system
Backup units are expensive, so most systems operate without redundancy — increasing risk

String Inverters

Advantages

Ideal and cost-effective for rooftop installations
Easy operation and maintenance
Flexible system configuration
Spare units are affordable and easy to store
Most brands are intercompatible and widely available

If possible, choose string inverters with advanced safety features such as:

AFCI (Arc Fault Circuit Interrupter):
Detects DC arc faults and automatically shuts down the system, preventing fire hazards in connectors or cables.
PID (Potential Induced Degradation) Recovery:
Reduces PID losses by applying reverse voltage to recover leaked electrons in solar cells, maintaining long-term performance.

Disadvantages

On high-risk or flammable roofs, long DC cable runs increase fire risk.
Additional safety measures are required.
The installation company must be a qualified EPC firm — untrained personnel should never work on DC connections.

Micro Inverters

Each panel operates independently, and DC power is converted to AC directly beneath the panel, eliminating the need for DC cabling on the roof.

Micro inverters are compact and come with 12 years or more warranty (excluding natural disasters like lightning).

Advantages

Each panel can be installed at a different direction or angle
Panels can have different capacities, models, or ages
No high-voltage DC on the roof — greater fire safety
System automatically shuts down during faults or short circuits
Individual panel monitoring allows quick detection of underperforming or faulty panels

Disadvantage

Highest cost among all inverter types

Optimizer

Optimizers are devices that support energy production by performing voltage optimization for each individual solar panel.

Advantages

Reduces partial shading losses — limits the shadow effect to the affected panel and prevents it from impacting the entire string.
High fire safety — in case of a short circuit, the system shuts down instantly and remains at a very low voltage level.
This ensures that during a fire, the DC cables are almost de-energized (near zero volts).
Minimizes mismatch losses — eliminates power losses caused by panel inconsistencies or performance differences.

Important Notes

Some optimizer brands work only with their own inverter models, which can cause operational difficulties.
Optimizers that are compatible with multiple inverter brands are more flexible and practical for operation.
Each device may introduce about 2% internal loss, so the overall gain vs. loss of the system should be carefully analyzed.
Reducing shading loss does not mean shaded panels produce energy — it only helps balance the string voltage.
Optimizers regulate voltage, improving string-level performance, not individual panel efficiency.

Summary

Advantage: Enhanced safety
Disadvantage: Slightly higher system cost