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Comment by mrec | Hacker News Reader

The impact of enabling WiFi on battery life hadn't occurred to me. Do you have a rough sense of how big the hit is?

Anecdotally, when we bought my girlfriend her first Kindle about five years ago, we noticed it was requiring charging way more often than the back-of-the-box battery life quote of "weeks of battery life". Upon calling an Amazon agent, they referred us to the fine print for that quotation:

> A single charge lasts up to six (6) weeks, based on a half hour of reading per day with wireless off and the light setting at 13. [0]

We were still pretty pissed at the blatant false advertising (a hardcore book reader reads for only a half hour a day!?!), but moving forward, she keeps the device in airplane mode 95% of the time, only turning it off to download whatever new book she just bought. It increased to at least 2-3 weeks after that, instead of a single week.

[0] https://www.amazon.com/Kindle-Paperwhite-Waterproof-Storage-...

The nice thing about the kindle is that with both wifi and light off, the battery use is nearly non-existent between pages. So the difference between 30 mins / day and 6 hours / day of reading is not that large, tbh.

Massive. Wifi only goes on when it's needed for something.

It's huge. I'd say around 10x (I have a 3rd gen Kindle)

And even worse with the 3G model if you are in a marginal coverage area. Didn’t discover a way to selectively disable 3G and keep WiFi on.

Comparing new WiFi model to new 3G model, out of airplane mode, the 3G drains about 2x to 3x faster than WiFi model.

My old Sony reader gets a few 1000 pages of read time/ 8 weeks (& more) or so of occasional use. On WiFi it drops to a week or so. Making an antenna work uses heaps of energy. It's worse when roaming as it searches for a known network.

A full charge on my older e-ink Kindle (whatever the last one that had buttons, rather than a touchscreen), can last for months with the wifi turned off. If the wifi is on, it usually runs flat in about a week.

Biggest battery drains on my laptop are usually the screen, GPU, and the wifi card. Usually very distant from no. 4

kindle displays don't use power like laptop screens. It uses very little power to sustain an image, and only uses more power to change the pixels.

You can keep the display of the kindle on for hours at a time with minimal drain

One of the key features of e-ink is that it actually requires zero energy to sustain an image. It only consumes energy for state changes between images.

Of course, modern e-readers have a backlight. Though you can never fully turn it off, at least on my first-gen Paperwhite, which is unfortunate.

Definitely going to be ereader-specific, my Kobo has a physical on/off button for its light.

Yes, that's why a wifi card being comparable to a laptop screen demonstrates how power hungry they can be.

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