Just faced the same problem, and just went through a lot of the reasoning that you are doing. Our experience, FWIW:
I was immediately thinking about two golf cart batteries as an emergency supply. Our stationary oxygen concentrator runs 375 watts. Figuring 90% conversion efficiency in the inverter, you need 417 watt hours out of the battery to run the concentrator for an hour, or 3,333 watt hours to run it for eight hours. At 12.5 volts, that's 267 amp hours. You're pulling current faster than what it takes to discharge in 20 hours, so you won't get the rated capacity. 215 amp hours won't get my stationary concentrator through the night, even without the CPAP.
I gave up and concluded that in an emergency, it was better to put the stationary concentrator in the back of the Trailblazer, and move that and my wife and her CPAP to a motel that has power.
If you buy your own POC, your insurance will likely continue to provide oxygen tanks. Tanks are probably the best and cheapest oxygen backup. We discussed it, and we think she can get by for a night using just oxygen and no CPAP if it comes to that.
Before we got the concentrator, I found a used EasyPulse5 pulse regulator on eBay for $80. That makes one of the little C size tanks last for 8 hours at 2 liters per minute. The E size tanks last 24 hours with the pulse regulator. That is a huge improvement in mobility. But, as you say, the tanks are a huge PIA however you cut it. And the pulse regulator will not work with a CPAP.
My search did not turn up the ActivOx unit you are considering. Their web page says that Medicare and most insurance companies will cover it. Maybe. What I found was that Medicare would cover the POC only if you start with that from day 1 of oxygen service. We were about 6 weeks in, and couldn't get one. We were told that Medicare pays for 36 months, and the POC provider needs about 35 months of that billing to break even. Possibly your deal will be much more favorable. I hope so.
We got the Inogen G4, which is very light and small. I suggest you price it at 1stclassmedical if you're interested.
Plan on replacing the molecular sieve columns after 18 months or so, and the battery after 500 charge/recharge cycles. For the G4, the column just snaps in and out and can be bought for $125. The batteries cost a ridiculous amount, but I haggled them down $100 by pointing out that they are available on eBay.
Watch out for charlatans. I asked one local supplier about the cost of changing the column and he quoted me $498, "and that includes labor." Ummmm.... what a ripoff! A 2 minute job, $125 materials cost.
Now the good news: Last week, my wife took her Inogen G4 and a spare battery, hopped in her car, and drove herself to the express commuter train station. She rode 75 miles, met her sister, plugged into her car, and drove another 75 miles to visit their mother. Apparently, they had a great visit. Then they reversed the process to get home. She got home with juice to spare, and without using the spare battery. That is in striking contrast to the initial situation, where she was almost home-bound because of the difficulty of carrying tanks. Getting the POC was a HUGE improvement in my wife's mobility and quality of life. She goes wherever she wants to go now.
Last edited by denton; 07/24/17.
