“Tankless heaters are really expensive, though right? Also, I heard that with heavy usage, even the tankless heaters can run short of hot water. No?”
Yes, and of course they give you less water per unit of time the colder the input water is. Unlike a tank, which is “ready to use’ at whatever flowrate your water pressure and pipe size will accommodate until it runs out. So if you want to take a shower at the same time the washer is filling, it’s a problem, but you never run out of hot water at the rate that the heater can provide. The other thing you need is a decent sized gas line and meter to feed it, because instead of a 30 or 40,000 BTU burner that runs for an hour or more to heat up a cold tank, the tankless needs something on the order of 180,000 BTUs to provide continuously hot water. The other thing that you have that controls the amount of water you get, and that’s just how hot you want it. Our tankless has DIP switches that you set to tell the heater how hot you want your water. The higher you set the temp, the lower the flowrate you will get. I think that we get around 5 to 7 GPM depending on the incoming water temperature.
We put ours in in 2002, and it hasn’t missed a beat. The other thing that you need is a type III vent because the heater has a blower in it to cool it off when you close the tap and the type III vent is gasketed (and stainless steel) so that there is no danger of CO getting out. They cost about 3x a tank.
Now that sounds complicated. *sigh*