A new study The energetic implications of introducing lithium-ion batteries into distributed photovoltaic systems” just released April 09 sheds new light on how much useful energy a solar system will produce over its life compared to the energy required to; extract all the raw materials, process them, manufacture, ship and install the final product as a working system. The study also looks at batteries.


Firstly, the study is already seriously out-of-date, for the input data it uses a 2013 study which itself uses energy input data from a study about solar panels and systems from 2011, at that time mono crystalline and poly crystalline solar panels were 14.1% efficient and came in a panel format of 1.7 x 1.0 m (approx) resulting in a 250 W panel.  Today Long has just hit a Mono-PERC efficiency record of 24.06% for a production sized cell. This means that we are going to see 370 W commodity priced panels within the next 12-24 months. That’s 150% the output of what the study was using in 2011 or an energy saving (not counting all the other savings which go even further) of 33%.


That would then take the EROEI estimate in the paper to 29; meaning the panel makes 29 times it’s energy back in the better locations and 14 times in the worst locations over its life. We could expect using the latest panels that this would go up to in excess of EROEI 40.


The good news is that batteries are improving and solar panels are improving to a point where commodity priced solar roofs will become a standard roofing option across the world.