Tankless water heaters provide “endless hot water” because there is no tank to run out. Tankless systems heat water “on demand” and never run out as long as there is a water supply. They can operate with both natural gas and propane.
“Instant hot water” means no wait for hot water to reach the fixture and is made possible with a recalculating loop which can be included with either tank or tankless water heater systems.
Tankless water heaters provide many benefits in addition to always having the hot water you need. For example, they do not waste energy to keep water hot when not being used. (Think about the wasted energy associated with keeping a big tank of water hot 24 hours a day.) They also take up much less space and can be located outside. Tankless is the default standard in many parts of the world and is gaining market share in the Seattle / Tacoma area.