thats not realy accurate, and it has been showen. the ondemand are not instant hot ewater heaters, they are fast but not instant. so when you open the tap there is a lag time before the burner erven turns on as the flow sencer has to pick up the flow then it does a purge cycle, ignition cycle and then starts heating the water. all that time the water has been flowing. with a hot water tank you also have heat creap up the lines so a lot of time the water is warm a few feet from the hot water and, and with the tank system it is pretty much instant.. you open the tap and full temp water starts leaving the tank, no waiting for sensors and cycles. now for the normal person that is just doing dishes and has a double sink so one for washing one for rincing, or that person that puts water in the bathroom sink to wash up for bed it probably isnt that big of a deal as we are probably talking 1/2 a L difference that can be used to temper the water temp in the sink. but for some one who uses the shower frequently and pauses the water several times during it (ie for soaping up, for washing hair, etc) then it starts to add up. now if you have hookups then its all a mute point as you have unlimited water and sewer capacity.. for me the other bonus is the extra 6 to 10 gal of water you get with the tank heater also.. might not sound like a big deal but when your trying to streach how long you can boon dock for.... water is my limiting factor now so every bit helps.