Choosing the Right PV System

Guidelines to Quality

A guide to a long-term investment

The decision to purchase a photovoltaic (PV) system is a long-term investment and for this reason must be selected with great care. The system is expected to operate at extreme weather conditions for over 20 years and must prove to deliver the electricity output (financial output) and performance but also to be safe and durable.

In principle, the selection of which PV module and inverter, and from which manufacturer/installer the system will be purchased, is a process that requires careful consideration.

total cost

The total cost of a PV system depends on the:

  • Power capacity of the system in kW
  • Quality of materials and technology used
  • Manufacturing batch and patented processes
  • Warranted period
  • Certifications and quality assurance standards


The definition Quality in photovoltaics summarizes all important parameters which are necessary for the PV to operate:

  • With safety and at high performance levels
  • Reliably and without outages over the lifetime of the investment
  • Keeps up with specified technical specifications and system designs

Selection Criteria

The main criteria to be considered during the selection of a PV system to ensure high quality include the:

  • Technical specifications of all system components (modules, inverter, and mounting system) as obtained by the datasheet of the manufacturer.
  • Quality standards and certification of the equipment
  • Product and performance warranty
  • Experience, quality assurance and past endorsements of the manufacturer/installer.
  • Quality of service offered by the manufacturer/installer before and after installation.

Technical specifications

PV Modules

Quality criteria for PV modules

  • Material type: Mono-crystalline, poly-crystalline Silicon

  • Cell technology: TopCon, PERC, PERT, HJT

  • Cell design: Half cut cells

  • Package type: Monofacial or bifacial

  • Peak power and tolerance (W): > 400 W

  • Efficiency (%): > 21%

  • Power temperature coefficient (%/°C): < -0.4 %/℃

  • Nominal Operating Cell Temperature (°C): <45 ℃(±2 ℃)

  • Bypass Diodes: At least 3

  • Glass cover: Tempered glass with high light transmission and anti-reflective properties

  • Junction box: IP67

N-Type VS. P-Type Solar Panels

PV cells consist primarily of a crystalline silicon wafer supplemented with additional materials to facilitate electricity generation.

In a P-type cell, a silicon base is doped with boron atoms to establish an overall positive charge, hence denoted as ‘P’ type. The upper silicon layer of the wafer is doped with phosphorus (N-type) to establish a p-n junction for electron flow. P-type cells are the predominant variant employed in solar panel manufacturing.

Conversely, N-type cells exhibit an inverse configuration compared to P-type cells. They feature a silicon base doped with phosphorus, resulting in an overall negative charge. The top layer of N-type silicon cells is doped with boron (P-type) to facilitate the formation of the p-n junction.

N-type modules

  • Immune to light and elevated temperature induced degradation
  • Long lifetime durability
  • Higher efficiency compared to P-type
  • More expensive than P-type
  • New production lines with few years of experience

P-type modules

  • More affordable compared to N-type
  • High experience in production lines and outdoor field use
  • High Resistance to Radiation
  • Suffer from initial light induced degradation
  • Lower lifetime durability compared to N-type


Quality criteria for inverter

  • Inverter design: Transformer-less

  • Maximum Efficiency: ≥98%

  • European Efficiency: ≥97%

  • Installation: Outdoor installation

  • Communication: Wired or wireless for monitoring

Mounting structure

Quality criteria for mounting structure

  • Frame structures: Anodized Aluminum alloy or hot dip galvanized steel
  • Bolts, nuts, fasteners: Anodized Aluminum alloy or hot dip galvanized steel

  • Panel mounting clamps: Anodized Aluminum alloy

  • Thermal expansion: The mounting system should be designed to consider thermal expansion. Expansion joints should be built into long sections of racking to prevent thermal cycling from stressing the rack or the modules.


Certifications for PV modules

General certifications

  • EN 50380

  • IEC 61215

  • IEC 61730

  • Class II Equipment certificate

  • CE marking

Additional test standards

  • Certified for salt mist corrosion test – IEC 61701
  • Certified for potential induced degradation (PID) – IEC 62804
  • Certified for ammonia corrosion – IEC 62716

Certifications for inverters

General certifications

  • EN 61000-6-1 or EN61000-6-2 (immunity)

  • EN 61000-6-3 or EN61000-6-4 (emissions)

  • EN 61010-1 (safety requirements)

  • EN 62109 (PV converters)

  • CE marking


Module and inverter manufacturers must hold a quality Assurance certificate ISO: 9001:2015 or equivalent, regarding the manufacture and sales of solar modules and inverters, respectively.
Top quality manufacturers ensure that:

  • Quality checks are applied on the production line.
  • Selection is made of quality products.
  • Investments are made to upgrade production lines and invest in research and innovation.
  • Consider high quality standards in packaging products.
  • Attention is given to customer experience and satisfaction.

Another important parameter is to select a PV module that is Tier 1 according to Bloomberg New Energy Finance (BNEF) classification since this indicates that the manufacturer has a strong track record of producing reliable and high-quality PV modules. These manufacturers typically invest heavily in research and development, quality control processes, and adhere to industry standards, resulting in products with lower failure rates and longer lifespans.

This can help ensure the success and longevity of solar projects by minimizing risks associated with quality, performance, and bankability.

Installation companies need to exhibit experience in the field, have technical training in relevant technical courses, ease of communication and reach, and low time for error resolution.


Warranty for PV modules

Product warranty
≥ 10 years

Performance guarantee
First year: > 98%
After first year: < 0.5% annual degradation

Warranty for inverters

Product warranty
≥ 10 years


Guide list

Download our guide with a checklist of the key parameters to look for when selecting your PV System