"They look at the unit, and it's so small compaired to a tank water heater, and they can't comprehend that it will produce enough hot water for them to take multiple showers at a time," EZ Tankless employee Mike Pavuk told wlfi.com. Pavuk adds "tankless technology has been around for 50 years, but it hasn't been widely available in the United States."
Instead, homes in the US typically use the storage water heater system (Drawing and text from the US Dept of Energy, linked here):
"It operates by releasing hot water from the top of the tank when you turn on the hot water tap. To replace that hot water, cold water enters the bottom of the tank, ensuring that the tank is always full. Because water is constantly heated in the tank, energy can be wasted even when a hot water tap isn't running. This is called standby heat loss. Only tankless water heaters—such as demand water heaters and tankless coil water heaters—avoid standby heat losses."The US Department of Energy says tankless or demand water heaters are up to 24%–34% more energy efficient than conventional storage tank water heaters. This is how the tankless system works:
"When a hot water tap is turned on, cold water travels through a pipe into the unit. Either a gas burner or an electric element heats the water. As a result, demand water heaters deliver a constant supply of hot water. You don't need to wait for a storage tank to fill up with enough hot water. However, a demand water heater's output limits the flow rate."To encourage home owners to switch, the US federal government offers a 30% tax credit for people who purchase a tankless water heater, according to the wlfi.com article linked above.