Stationary oxygen concentrators are for home use because they can only be plugged into an AC outlet. They're also usually larger than portable concentrators, so you wouldn't want to have to transport them around, anyway. Even so, stationary oxygen units are still necessary and make the lives of oxygen therapy users easier.
If you only need to use oxygen therapy a hours out of the day, a stationary model might be a better decision, because portable models can be much more pricey. You might only need to use it overnight, and you don't plan on doing a lot of traveling to other places where you would be staying overnight. If you would generally only be using your oxygen therapy while you're at home anyway, a stationary oxygen concentrator is the way to go.
Here is a comparison of the high flow, mid-sized and small stationary models and why each one might be better for you than the others.
Small Stationary Oxygen Units
The Respirionics SimplyFlo is the smallest stationary oxygen concentrator and is about the size and weight of a mid-sized portable unit. This one is fairly new but only puts out up to 2 LPM of continuous flow. If you only need this much oxygen, you do a lot of traveling, and you only use it overnight, this is the perfect stationary model for you.
Another of the most notable is the AirSep VisionAire 3. It only weighs 30 lbs, but can still deliver up to 5 LPM of oxygen. It's settings are 1 through 5, and it's also one of the quietest and most energy efficient. If you need continuous flow oxygen up to 5 LPM, the VisionAire 3 is a great option.
Mid-Sized Stationary Oxygen Units
The Invacare Perfecto 2V is a great mid-sized stationary concentrator. It gets up to 5 LPM, but can also start as low as 0.5 LPM. It's only 43 decibels, which is about as loud as a refrigerator when it kicks on. The thing many people like the most about the Perfecto, is how energy efficient it is.
High Flow Stationary Oxygen Units
The best performing stationary oxygen concentrator for its weight is the Respirionics Millenium 10. It stands at only 18 inches wide, 27 inches wide, and weighs 53 lbs. It has some of the best technology to make it the highest performing, with settings from 1 to 10 LPM.
If you need more than just a oxygen concentrator, the AirSep Intensity 10 would also fill your needs as a nebulizer machine. It weighs 58 lbs and sits at 27 inches tall, but it's more machine than the other larger end stationary units and has more features.