They Are Not Really Instant

As long as you
choose the right product and get it installed properly, there are countless
good things about having a tankless water heater in your home. But contrary to
the belief that some marketers are relentlessly trying to promote, providing hot water instantly is not one of those good things. In order to avoid disappointment and to be better informed about tankless water heaters, this point needs to be made clear.
Unlike tank style hot water heaters, tankless units heat water as it passes through the heat exchanger so cold water enters the units and heats up to the desired temperature within seconds before leaving the water heater and go into the hot water pipes. What happends after this point is exactly the same as what happens if you have tank water heater. Hot water must travel through the pipes in your home, all the way to your shower head or kitchen faucet and for that to happen, the cold water in the pipes must flow out of the water outlet. In other words, even when you have a tankless water heater in your home, hot water will take time to reach you and this is why calling tankless water heaters “instant” is a misinterpretation if not a gross marketing mistake.

But They Are Still Better

Though you should not be excepting hot water gushing out of the shower head the moment you turn on the hot water handle, tankless water heaters are still faster than tank water heaters in some ways. For instance, when you just turn on a hot water tank after a few days of staying shut down, there is no way you will get hot water in less than hald an hour because it needs time to heat up all the water inside. On the other hand, a tankless unit has such powerful heat exchangers that it needs zero recovery time. As long as the cold water in the pipes goes away, you will have as much hot water as you like.