Has anyone replaced a hot water tank with an instant hot?

What do you seek to improve? The current water heater is there and works just fine as-is, right? At no extra cost.

Instantaneous heaters usually need a short time to reach the desired output heat - some extra water is probably wasted that way.

Usually, fresh water is a more limited resource when traveling than LPG.

You would also reduce your fresh water reserve by the 6 gal. in the boiler tank.

In winterizing it might save a few minutes.

I installed the "Hot Rod" electric conversion in my 6 gallon tank. I like it. When the RV is plugged in, my water is hot without firing the LP! Most of the on demand heaters have a large electric or gas pull to heat the water on demand.
Brian

I'm in the same boat regarding not using the water heater much at all. I do test it each year to make sure it's functioning, but don't really use it. Never really thought of going the instant hot water route as I agree that the current water heater does a fine job when needed. Most trips i run with it empty so not carrying the weight. The only need I have for hot water is doing the dishes so I just heat up some water in a pot on the stove and dump it in the sink. Heats up quick and only the amount I need, not six gallons.
I have heard of others changing to instant hot water so I would assume size wise it should fit just fine in the same spot your current heater is.

Any links you could provide for those other mentions? I generally just put a bit of water in the pan after cooking and it heats enough to do dishes quickly before eating. We use disposable plates and plastic silverware so cleanup is deciding if the forks need rinsing.

But I have never showered in the camper due to it being a wet bath and the wasted water. I usually wash my hair in the kitchen and washcloth the rest as needed. Because it's quick, my cleanup is COLD without hot water.

https://m.youtube.com/watch?v=RyCvLhc8Pm4

This video shows the Truma unit going into a fifth wheel with a 12 gallon heater. Sounds like the Truma has adaptor plates though to conform to different sized openings.

Cobra21 wrote:
I installed the "Hot Rod" electric conversion in my 6 gallon tank. I like it. When the RV is plugged in, my water is hot without firing the LP! Most of the on demand heaters have a large electric or gas pull to heat the water on demand.
Brian

I did that when we sold the house and have been living in TC for time being.
Not only "hot rods" operates on electricity supply by campground, but heating element is placed lower than propane burner and thermostat can be set higher.
So I've been enjoying 10- minutes showers in those days. Recovery was long, but fortunate DW takes shower at different time.
There are lot of myths about tankless WH.
Working in construction and being landlord - I had my share of dealing with them.
For rental units tankless is only that I install. You can buy small one for $60, but that is battery-operated, or $100 buys you bigger one that plugs into 120V.
When they are very practical for landlord, it is the tenants who deal with inconvenience of temperature surge and need for opening high flow for the heater to ignite.
Would I install 1 in my own house? I am not sure as often I need hot water to drizzle and tankless will not work with it. Also water circulation pumps don't always work with tankless.
For big house probably the best combo is tankless with small tank heater for temperature stability and high output.
Coming to RV, even I realize that I carry 6 gallons of dead weight in my WH, I am too cheap to spend money for replacement.
And again, fact that campgrounds pay for my water heating is good part.

I have never camper at a camp ground. The only time I use the TC I'd boondocking in a field in the middle of nowhere. My dad installed a tankless in his shop so I assume it worked well enough (never heard a complaint. He replaced a tank with a tankless dedicated to a sink which is the same reason I would in my shop. I hadn't head a downside for sparing use of hot water which is why I was considering it for the TC.

Keep the comments coming. They are very interesting!

Fwiw
Interesting Custom made water system in a custom built TC

https://youtu.be/1THtBYxu8N8

Most of the gas units take anywhere from 20 to 30 seconds to get the water up to temp after you open the tap, as soon as you shut the tap they shut off. So if you do a navy shower every time you turn off the water for soaping and back on to rinse and such you will get a 20 to 30 second shot of cold water.

How about the UL listing? Is it designed for RV applications? Any greater fire hazards? I think these might be important questions.

Personally, I like the 6 gallon that helps me to conserve use of the grey water tank and freshwater tanks.