Originally Posted by moffattm
Thanks for confirming that for me. So the amount of memory that a book uses should have no affect on power usage while the device is asleep.
I can understand poorly formatted ebooks (i.e. books that have all their chapters in one huge file instead of splitting into multiple smaller files) having an affect on the processor (i.e. making the processor work harder by having more data to shunt around), but this should only be while you're opening or reading the book, not while the device is asleep. Do you agree?
In general, in sleep mode, the size of the book should not be a factor in battery usage. During sleep mode, the processor should only be refreshing memory, and looking for a hardware interupt, which in this case is the power button being flicked or the usb cable being connected.
It may be possible for the processor to be smart enough to only refresh part of the memory, but then you have to be able to tell the processor which parts of memory are containing valid data. My opinion is that both the Kobo firmware and the processor itself is not up to this task. If they were using an ultra-low power processor, then maybe.
So, during sleep mode, the battery usage should only be dependent on the requirements to keep the memory refreshed and scan for the hardware interrupt (if it has to scan for this), regardless of which book (or any) is currently loaded.