A lot of solar PV modules are nowadays available in the market. Having almost the same technical nameplate ratings and warranty terms, many times it becomes very difficult for an EPC player or end-user to select the right solar PV module for their rooftop solar PV system.

This article will discuss which factors should be considered while selecting solar PV modules for rooftop solar PV projects.

The Efficiency of Solar PV Module

There is always a wrong conception people make regarding the efficiency of PV modules. It is not always correct to say that if we select a higher efficiency module then we will get higher energy output. Let us understand how efficiency affects energy output from the project and how the efficiency factor should be considered before selecting a solar PV module.

Sample PV module datasheet

In the above figure, it can be seen that different power rating modules have different efficiencies and the same physical size. Let’s consider 480 Wp module with an efficiency of 20.1% and size 2176mm x 1098mm and see how efficiency is calculated for this:

Efficiency (%) = [Rated Power of Module at STC x 100] / [Irradiation at STC x Area of Module]

Efficiency (%) = [480 x 100] / [1000 x 2.176×1.098] = 20.1%

Now let’s consider two scenarios and see the effect of efficiency under those scenarios:

Scenario 1:

Option 1: 10 kWp system with 480 Wp module (20.1 % efficiency)

Option 2: 10 kWp system with 505 Wp module (21.1 % efficiency)

Under this scenario, we have an option to select from either 20.1 % and 21.1 % efficient modules. Since the installed capacity of the system is fixed i.e. 10 kWp, it does not make any difference whether one selects 480 Wp or 505 Wp module. Energy output will remain the same in both cases.

Scenario 2:

Option 1: 20 Numbers of 480 Wp modules (20.1 % efficiency)

Option 2: 20 Numbers of 505 Wp modules (21.1 % efficiency)

In this scenario, since the number of modules is fixed, energy generated from 20 number 505 Wp modules will be more than energy generated from 20 number of 480 Wp modules. The reason for higher energy is the higher installed capacity of 20 number of 505 Wp modules (i.e. 10.1 kWp) when compared to an installed capacity of 20 number of 480 Wp modules (i.e. 9.6 kWp).

A higher efficient module will not be beneficial if the installed capacity of the project is fixed. However, a higher efficient module will be beneficial to meet the higher energy and higher installed capacity in case roof space is a constraint.

Hence, one should select a higher-efficiency solar PV module when there is a space constraint to meet the expected solar PV installed capacity.


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