IMHO, it's a bit academic. When was the last time you had a power outage lasting more than a couple of hours?
1. Wake up (it's pretty automatic if the machine stops.)
2. While the rest of you are finding, connecting and worrying about how much charge your battery has, I'll be reading a good book and waiting for power to come back on. When it does, I'll be sleeping before y'all get re-rigged for AC.
3. If more than an hour or two, I go back to sleep for the rest of the night without CPAP
. (Yes, I hear the collective gasp!) After all, it isn't "life support". Sure, it's better to have the therapy, but will one partial night kill ya? How many nights did you sleep with apnea events BEFORE you had CPAP?
4. If it looks like the power outage will be longer, I'll evacuate to somewhere with power. And while we're traveling, guess what? As long as the car is running, I have an endless supply of 12VDC! (Of course, trying to sleep while my wife is at the wheel is another challenge altogether...lol)
But, seriously, I think way too much is made over alternative power sources. Unless you are addicted to recreational camping, I just don't see the need.
That being said, I DO have a "jumpstart" battery I use with my telescope. I've never tried it with my CPAP, but the 'scope has the same PWR jack as the CPAP. It's 350Ah...guess I could do the math and see how long it might last on CPAP, but I've really never felt the need.