What Is A Tankless System


While a standard tank may heat and reheat water even when you're not at home, tankless water heaters, also known as demand-type or instantaneous water heaters, provide hot water only as it is needed. Tankless water heaters don’t produce the standby energy losses associated with storage water heaters, which means lower energy bills and more money in your pocket.

Tankless water heaters heat water as it goes through the pipes, giving you an endless supply of hot water for your family or business. They also have a longer lifespan, about twice as long as a regular tank. Plus, tankless water heaters have lower maintenance costs allowing you to easily replace parts rather than the entire system.

Tankless water heaters are about 90% smaller than standard hot water tanks and can be installed in compact or non-traditional spaces.

Tankless vs. Tank

If you grew up in a home with lots of people taking showers and running appliances, you’ve probably experienced what it feels like when that big tank runs out of water. Not too fun, is it? So how can this box, about the size of a suitcase, mounted to your wall keep your showers hot and your tubs full?


  • Cold water enters inlet pipe only when hot water is required
  • Gas ignites heat exchangers, which heat the water
  • Heated water exits hot water outlet to travel through pipes to where it is needed
  • Heater will adjust flame output as needed to ensure temperature set point is maintained
  • When no more hot water is required, system shuts off until hot water is needed again


  • Large tank requires more installation space and management
  • Water in tank is heated and reheated to maintain desired set temperature regardless of usage or demand
  • During times of heavy use, water can be depleted, causing delays in hot water supply
  • Product lifespan of a tankless unit is twice as long as that of a traditional tank (based on DOE Energy Star lifecycle estimates)
Tankless Water Heater: How It Works