Solar panel efficiency measurement

What is Solar Panel Efficiency?

Solar Panel Efficiency is the ability of the panel to convert sunlight into electricity. For example, if two solar panels of same physical size but different efficiency ratings are placed under the same amount of sunlight for the same duration of time, then the panel with a higher efficiency rating would produce more power compared to the one with less efficiency rating.

Advancements in technology are taking place at a rapid rate. You would be happy to know that efficiency of solar panels to convert sunlight falling on them into electricity has increased from 15% to 20% in recent years. The market is now flooded with the most efficient solar panels. Jinko solar recently launched Higher efficiency PV module with a power output of up to 580W.

How are solar panels efficient?

As we know, panels are made up of several Photovoltaic cells that convert the sunlight falling on them into electricity. The amount of electricity produced by them, in turn, depends upon the cell’s composition, electrical configuration, surrounding components, and more.

The efficiency of cells inside the panels is always higher than the overall solar panel efficiency. It is because when they are placed inside the panels, they get prone to losses due to the physical layout of the frame, connections between cells, and optical losses from being enclosed inside a glass.

Solar panels or modules are tested in laboratories under Standard Test Conditions. STC are industry-standard conditions used to measure the amount of power produced by different modules under the same conditions.

Standard Test Conditions are as follows:

1. The temperature of the cell should be 25ºC.

2. Solar irradiance level should be 1000W per square meter. (This is the amount of light energy falling on a given surface at a given time.)

3. Air mass 1.5 spectra.

How efficient are solar panels?

Most Efficient solar panel manufacturers and models currently in the Market 2020

Manufacturer Model Wattage Efficiency
SunPower Maxeon 3 400 W 22.6 %
LG Neon R 375 W 21.7 %
REC Alpha 380 W 21.7 %
Jinko Solar Tiger Mono-facial 390W 20.74%
Longi Solar Hi-Mo X 355 W 20.3 %
Qcells QPeak Duo G6+ 350 W 20.1 %
Jinko Solar Cheetah HC 340 W 20.1 %
Trina Solar SplitMax 335 W 19.7 %
JA Solar JAM60S10 330 W 19.6 %

Solar panel Efficiency in real-world conditions:

The real-world conditions are quite different from STC, and they vary almost every day. To give you more clarity, let’s take an example for reference. A 250W rated solar panel with 15.1% efficiency means if 1000W of light energy is falling on panel (per meter 2) having a cell temperature of 25ºC, then it would produce 250W of power by converting 15.1% of light energy falling on it into Direct Current.

Do you want to know what can affect your solar panel efficiency in the real world?

1. Shade

2. Temperature

3. Dust/ Dirt/ bird droppings

4. The angle of orientation 5. Location (latitude)

The most prominent among the aforementioned factors are the shading and bird dropping. If your solar panel is covered with shade then its efficiency would reduce drastically so it’s very important to pay attention towards it. With time trees grow and sometimes they start to block the sunlight from reaching panels. Other than shading, bird dropping need your attention as they stick to the panels and don’t go away easily with rain and wind. As long as bird dropping has covered your panel, your efficiency would be reduced. If you need help with panel cleaning, read our article here which explains ways to clean solar panels. You can also bird-proof the solar panels on your roof. Click here to know-how.

Why does solar panel efficiency matter?

Payback Period

We can’t deny the fact that high-efficiency solar panel pay pack faster compared to less efficient panels. With solar panel efficiency increased to 20%, the pay pack period is just around 2 years now. In addition to repaying the upfront cost sooner, it will generate more electricity over the period of its lifetime (standard 25 years).


The area occupied by the panels has a significant role to play while choosing solar panels for home. Solar Panel Efficiency matters, but it is not the only factor to consider. As the panel efficiency is directly proportional to electricity generation per m2, this means a more efficient solar panel will take slightly lesser space than a less efficient panel. If you consider roof space, the high output solar panels should be your first choice. Currently, the majority of the panels have an efficiency between 15% to 20%. Only very high-efficiency panels go up to 22% or 23%.

Check out the specifications of solar panels/ Inverters / Batteries of top brand.