Husband has a concentrator that is hooked up to his BiPap machine at 3 liters for sleeping. Easy to use a concentrator, just turn it on, and put on the canula and stick it in your nose. Then you don't have to fuss with bottles. Runs off electricity. And a solar charged battery (we've done it) We have bottles, too, the big ol green ones. Those are a pain to lug around, and depending on how many liters you have it on, it may not last all night. We emptied all of ours when little Brenda the neighbor girl needed O2. Just had them refilled. We also have a portable pulse ox unit. They're over a thousand to buy, but it's worth it to have for husband. Lightweight, has a shoulder strap, too. His is an Inogen One, and we've seen them cheaper used, too. Today I put it on the back handle of the wheel chair as I pushed him to his appts all day. We have two batteries to it, one lasts all day. We use it when we're out and in the car alot. But it gives you oxygen in a pulse, not a continuous like what he uses for sleeping. Medicare covers alot. After you do the pulmonary function tests (yearly) and possibly a sleep study.