How does this work can we get more info? Is a higher number better? Is this how fast it charges? What is the scale for changing that number? Thanks in advance!

The efficiency is the efficiency in which it charges. So if a battery is using a 100% of its max output and you try to charge it at 0.8 (80% effi) then it can't charge or keep up with the output. If its 1.0 (100% efficiency or over) you can charge and deplete or essentially passthrough the charge without any loss. If the efficiency is over 1.0 then you can gain and store energy at the same time.

Rust defaults to 80% (0.8)
On my server I do 100% (1.0)

Higher the better. :)

Nice, thank you for that info! Yeah I figured 1 was 100%, just want to make sure I was on the same page. 1-1 is a much better ratio for make electrics simpler. Thanks for the plugin :)