To answer this, we must first explain how a tankless system differs from a storage tank system. A storage tank system works by reserving hot water until it's ready to use. So the hot water supply in the tank can run out and it takes a while for the electric heating elements or natural gas burners to refill it.
A tankless system doesn't have a limited supply of hot water. Instead, the water heater heats water as needed. When you switch on the hot water shower, the tankless system detects water flow inside the lines and begins heating it via a heat exchanger. It will do this as long as there is demand, so you will never run out of hot water.
But you need to consider the following: even if a tankless system never runs out of hot water, it might be overloaded. You can run a single shower all you want and still get hot water, which makes the heater struggle with offering you a constant flow of hot water.
As a result, we advise working with experienced water heater installation before going tankless. Your water usage pattern may benefit from a storage tank. Or you could build multiple tankless systems.