That's what is happening most times; tankless provides the excuse to waste water with the fringe attitude that it's a cost saver because it's not heating stored water.
99% of the tankless units installed are in homes where the property owner does not know how to work on them. It's a guessing game from the word go.
Does not matter if they have the internet at their disposal; if something happens to them, or if they move, die or become unable to work on that unit to save a buck...
that pushes either the next owner, the wife, or talking to 6 neighbors and one that has a box of tools to try and figure out what makes that box on the wall tick.
But I get defensive statements thrown at me when I write like this, the ones who spent hours upon hours on their tankless purchase going over everything and proud they hung that unit on the wall. That's great, it's admirable...but remember the down-the-road costs.
You do not have parts at your disposal most times. Especially years later after the model on the wall is 4 models changed since then.
In a house with no hot water for days.....against a house with no hot water for hours is a BIG difference, completely.
Of course; I'm talking of the down side to these equations regarding tankless...but I'm a service plumber. I'm the guy everyone calls when there's big problems in little china and the world has stopped at your doorstep until the plumbing is fixed.
So when I see any product relating to plumbing, I have to know how it breaks, what it costs, what I need to do to make that product reliable.
I know if I am dealing with a Kohler faucet...be prepared for misery and let down. It's coming. Multiple trips and no guarantee that even the new products straight from Kohler themselves is going to work. Si? Si.
Everybody loves new technology, wants to be part of the "wave" and tankless will give you that. They are a sure bet out west; if the incoming temperature of the water is relatively high to begin with, these units do a good job, a great job because the temp rise is less than 40 degrees to do so.
Come out to the eastern states, northern states and that's where you'll find out that 50/60/70 degree temp rises are the norm...and that takes a flame thrower on the wall to keep that water moving fast.
You have to spend money on these units annually. You have to decalcify those units with a pump and the mixture. That's X amount of dollars for that pump, then X amount of dollars for the chemicals to clean what you cannot see, just gauge by the color of the water mixture. 45 minutes or somewhere around there.
Given that the majority don't ever drain their water heaters once a year...now you're going to spend this much time on your tanklesss...or are you going to run it till it breaks?
I already know this answer from the 1000's of homes I've worked, and nature of this profession of plumbing and people use their plumbing till it breaks. Having a select few rogue opinions come at me because they take care of their plumbing like they do their hair won't match up in the cards of reality and what all plumbers see on a daily basis.
I wish people would take better care of their plumbing but it's always profitable for me that they don't. These tankless heaters, when they become popular in the next 10-15 years will be cash cows for plumbers for a multitude of reasons...starting with the #1 buying choice that most property owners are so guilty of:
Purchasing by price instead of quality
Example? Buying tankless heaters at big box stores, online, bought through recommendation because a buddy has one and his works well.
I applaud your good deal, but I will be charging for standing in front of your outdated product from the word go and I will charge for every minute I have to spend on the phone in your home at my shop in my truck or before I go to sleep to figure out what part fixes the puzzle.
That's only fair because I didn't buy your magic box that makes hot water, you did.