The 12v solar panel market in Australia is about as bad as Aliexpress. Advertised panel outputs are grossly exaggerated, usually by 200-300%.
This post will be short and sweet, but some very simple math allows us to work out rough outputs from the panels available on eBay and even reputable retailers such as 4×4 Supacentre and online marketplaces such as www.catch.com.au.
A solar panel is usually something like 15-18% efficient in the 12v marketplace. It is extremely rare that they will actually output 20% or higher and if they do, they are probably 10x times more expensive than what you are looking at paying on the online marketplaces.
An example of what to expect from an eBay 350w solar panel is probably something like 80-120W. If you work out that 1000w of sunlight falls per metre squared that is STC and the panel is 1270mm x 710mm and area of about 0.9m2. You can multiply that by 0.15 (15%) to get the wattage (if you need the calculation, do a google search). So, anyhow 0.9 x 0.15 is 135w. Now add in the NOCT rule of thumb, reduce that number by about a quarter and you will get 101w of power from that solar panel under normal operating conditions.
Given that you are paying about $170 for that panel. You are actually paying far too much for those solar panels you buy online and losing valuable roof space as a consequence.
Some people have caravans and off-grid requirements, so recently people have been looking to the house panel marketplace, this is a better option but only if you have the space available to install that size panel, and it also means your voltage may increase, which is fine as long as you take that into consideration.
It is illegal in Australia to work on any DC electrical system or panels with a voltage higher than 50V DC. This means you need to ensure you don’t run the panels in series of anything higher than that number unless you are a licensed electrician with the appropriate qualifications.
There are some exceptions to the marketplaces with Vendors such as Renogy. They actually do offer a more realistic wattage for their products, of course, you should still take roughly a quarter off the advertised wattage, because of the NOCT (normal operating conditions) rule. But at least you know what you are actually buying.
We will soon create a buyers guide and even list some good quality products on our website, so you don’t have to get ripped off buying completely rubbish claims made by online retailers.
