Solar Panel efficiency explained


We love the chart above produced by the NREL for its mind-boggling detail, and if you want to read their report on ever increasing solar panel efficiencies over time then this is their web page link.


To explain solar panel efficiency, you first need to know that in a solar panel factory they test their panels with an intense burst of 1000 Watts per Sqm of artifical sunlight. The panel then produces electricity, and just how much electricity it produces determines it's rated 'watts'. So, in 2020, it might well produce 370W, but back in 2012 the same sized panel produced 200 Watts.


So, to calculate the 'efficiency' of a solar panel you first take the physical size of the panel.


Let's take the Jinko Cheetah 370W half-cell mono panel as  our example.


So this Jinko physical size is 1796 x 998 mm = 1.792 square metres.

Now we multiply that by 1000 (remember the flash test of fake sun?) to get 1792.

We now divide the 370W output by 1792 and we get 0.2065

So the efficiency of this Jinko panel is 20.65%

So, it converts just over 20% of the sunlight that hits it in the test, into electricity.


The main point you should take away from this is that you need 18 of these 370W panels to achieve the typical 6.66kW that we are currently limited to in Perth residential installations.


If the panels were 390W (e.g. JinKo Tiger) you would need 17 of then, or 19 if they were 350W. So all efficiency really ends up meaning is 'how many panels you need to achieve 6.6kW". A couple of years ago 300W panels were common, so 20 were needed, and a few years before that 275W was the norm, so 24 panels needed.


Jinko recently (June 2019) broke the World record for efficiency with 24.2% but we will never see THAT panel here in Australia, we only get the regular stuff as there aren't enough buyers here with deep enough pockets for that level of technology but wait another three or four years, and that level of efficiency is likely to be run of the mill.


65 years ago regular solar panels were 1.2% efficient

15 years ago , 10% efficient

7 years ago, 12% efficient

2 years ago, 17% efficient.

In 2020, 20.65% efficient