Screenshot_2016-01-30-21-50-14This is a post for those times when your ereading device is running low on juice and there’s no wall socket to hand. (In-flight use, for just one example.) And of course there are the usual ways, such as dimming your screen, turning off WiFi, switching the device into low-power mode, etc. But there’s more than just this to consider. Most keen ebook enthusiasts, and certainly Yours Truly, have more than one ereading app or type of ebook on their device. So which ebook file type and which reading app are the best options if you really want to stretch out your remaining charge?

To test this, I installed the well-regarded GSam Battery Monitor on my $50 Amazon Kindle Fire, though the software should work fine on any other Android device or smartphone. There’s actually a Kindle Fire-optimized version of GSam Battery Monitor available on the Amazon Appstore, but that also costs money, while the basic app is free. Still, if you want to spend money on it, it’s there.

I ran an ad hoc test by opening three ebook readers side by side: the Kindle app, Mantano Reader Free for EPUB ebooks, and Drive PDF Viewer for PDFs in my File Expert HD file manager. Just to be sure, I also opened one browser tab in the Fire’s Silk browser to read an HTML text. Then I compared the battery drain via GSam Battery Monitor, trying as far as I could to keep all the apps open, and scrolling through a few pages in each one at a time. This certainly isn’t the most scientific test ever devised, but I thought that even then it would throw up some interesting pointers. I wasn’t wrong.

As you can see from the above screenshot, the biggest battery hog was the Kindle app – not unexpected, actually. Second most demanding was Mantano Reader Free, but still with only half the drain of the Kindle app. Third was the Silk browser, and fourth, interestingly, was the PDF viewer.

Given the Kindle app’s bulkiness and the perennial complaints about Amazon’s barely passable coding, its poor battery life isn’t a surprise. GSam Battery Monitor actually allows analysis of what each program is doing, and the Kindle app just seems to have a much higher demand on CPU usage: 1 minute 19 seconds versus just 41 seconds for Mantano Reader Free and only 25 seconds for the Silk browser, in one 14-minute comparison period.

As for the PDF Viewer, its great battery conservation may be a function of the type of program it is. A more sophisticated PDF app, such as Adobe’s, may draw more power by turning virtual pages and other bells and whistles, instead of just displaying the whole document at once. If you have more than one PDF reader on your mobile device, and want to conserve battery life, use the simplest, seems to be the obvious advice.

Overall, looks like we have a clear conclusion here. If you want to extend your reading time to the maximum on the Fire’s battery, or any other device, with your choice of ereading apps, read a PDF ebook or a single text on an HTML page. Or if you must, open an EPUB ebook with one of the usual readers. And avoid the Kindle app if you have any respect for your battery. Just as well for Amazon that USB chargers are so compact and wall sockets so common these days, eh?


  1. If you really want to extend your battery while reading, switch your reader to “night mode” or the equivalent. The display uses a lot more power than the CPU when reading, so having the screen mostly black will vastly reduce power usage. Also, turning off the wifi is a necessity for some tablets, although the Fire seems to be better about its own power management than others, so it may not be necessary.