Off the top of my head, I think 'on' average power consumption was ~700uA without wifi, and about 1.5mA+/- with Wifi. This is from over a decade ago, so my memory is fuzzy though...
Obviously, page changes used relatively large amounts of power. I don't recall the exact amounts, but it was 100s of mA for seconds.
There is also an "every x pages, do a full screen refresh (black to white)" to fix up the ghosting issue that the article writer saw.
I did the same last year and had lots of fun in the process.
Your post is making me want to try more Cloudflare Developer Platform stuff like Cloudflare Workers.
You can regularly find the Kindle Fire HD10s for ~$40
The "electric sign" app does this, which is where I referenced the code.
With trmnl, the image only refreshes every 10 mins so the device will set a ~9 minute alarm to wake the device right before it needs to load the next update.
The refresh period is also configurable so a slower refresh interval (e.g. every hour for less time-sensitive screens) yields larger battery savings
Dyson vacuums and Kindles are not the same whatsoever, but I wonder how easily it'd be to swap out the battery on an older Kindle. For our vacuum, all I needed was a 20 dollar replacement battery and the will unscrew 3 mini screws.
I understand there's like all sorts of complexities in standards, form factors, voltage, wattage, etc, but I really wish I could upgrade my old devices like that.
The Kindle browser is surprisingly decent, I made Claude Code generate an RSS feed reader compatible with the Kindle browser, with the ability to read full articles (for those feeds that require you to visit the website), and download articles. It also supports Reddit and Google News RSS feed. This is my new favorite way of browsing the internet.
I also didn't want the browser bar at the top.
After going through this process though, I'd say as long as somebody has basic linux knowledge, chances of bricking are pretty low.
For a defunct startup, I built this exact thing as a product for coffee shops:
cafetren.com.ar
https://cafetren-com-ar.translate.goog/?_x_tr_sl=auto&_x_tr_... (translated from spanish):
A small solar battery is a VERY interesting idea. If I don't end up being able to hit that number by adjusting the code itself, will look into it.
Bus stops in Shanghai have e-ink displays that are kept up to date with the current estimated arrival time of each bus. (I don't know what the time resolution is; it could be 60 seconds, but not much longer than that.)