Hot water heater LP gas

It is like a traditional water heater. In addition, one has to get the hot water from the tank and through the lines to get to the point of use. It is not instant.

Being that it is only 6 gallons, it does not take too long. I haven't timed it though so I can't say how long. As for a shower, unless you are hooked up to both water and have the gray tank hooked to a drain, you would not want to run the shower enough to drain the tank anyway. If you are dry camping, you run just enough to get wet, pause it, soap, and run enough to rinse. Otherwise, you would drain your fresh water tank and fill your gray water tank in short order. If you are at a campground with full hookups, it is usually still more convenient to use the shower facilities there. With the small, wet shower of the 179, there isn't much maneuvering room, so the facility shower has the benefit of more room and no worry about running out of hot water in the middle of the shower.

Speaking of showers the Vermont State Park system is switching over to solar heated hot (and I use the term loosely) water in their shower facilities. It seems the newer facilities have the solar and the older ones still use propane. After our recent experience at Elmore State Park in Vermont I suggest the old facility if available if you want a HOT shower. While the newer bathrooms are very nice the water is tepid at best and cold early in the morning. 

We have taken 4 showers, pretty much one after the other, and not run out of "hot water" in our pod. This is taking navy style showers. Unless you have full hook ups, long showers are not what is in your day anyways.

Gotta do Navy showers with a 6 gallon heater.  Recovery is fine between showers, you just can't run it nonstop during the shower even with full hookups and propane + electric running at the same time.