On-demand water heaters eliminate the use of the storage tank, which as we learned above, heat the water and store it for use at a later time. The on-demand system operates just as the name implies. The water is on-demand and heated as soon as it's needed for showers, faucets, washer machines, and dishwashers. As soon as the hot water is called for, the cold water flows into the heater and triggers a flow sensor. This flow sensor activates the heating element within the space heating system. At this stage of the process, the water is pushed through the coil/pipes that are now prepared to heat the water for use. Of course, there are advantages and disadvantages to this system, just as there are concerning other options. One major advantage consumers express is the reduced chance of running out of hot water like you would with a storage tank. However, each situation is different and it's best to discuss options with your professional to discuss the best course of action for you and your family!