Tankless water heaters are also known as on demand water heaters or instantaneous water heater. A whole house tankless water heater can reduce your water-heating bill by 5 to 50 percent.

As the name suggests, a tankless water heater do not have any storage tank. Tankless water heaters can use gas or electricity and fuel. These water heaters are further classified as “whole house” or “point of use” water heater. These water heaters are more expensive and have complex installation process.

In the “Tankless Water Heater Buying Guide,” I have already explained how whole house tankless water heater heats water moving through the system instead of heating a large tank filled with water.

The supply of hot water can be unlimited with a tankless water heater. Because there is no tank, there is no need to empty the water heater with any tall bath because. This means that capacity is not an issue with a tankless water heater. The issue is with the flow of hot water. A tankless water heater is never going to “run short” of hot water until and unless the flow surpasses the water heater’s ability to heat water. Controlling the flow of water to bathtubs or dishwasher or any other appliance is recommended so that you don’t it doesn’t run out of hot water.

Most whole house tankless heaters have burners that are gas-fired (propane or kerosene). Because of the heat output and response time required, Gas-fired tankless water heaters require venting. Some water heaters also have power vents to exhaust gases out a side wall. Companies such as Rinnai and Bosch also make water heater units that can be installed outside the home and do not require venting.

Some models of whole house water heaters have pilot lights while some have electronic ignition that may require electrical hookup. One Bosch tankless water heater utilizes “hydro ignition,” a tiny water-powered turbine that sparks the burner.

Water Heaters that don’t require a pilot light are more energy efficient but are also more expensive.

Compact sized sealed combustion water heaters are good for places with limited space such as in an attic. Rinnai tankless water heaters utilize a cool-to-the-touch vent system for such locations.

While buying a whole house tankless water heater, be sure to check out the warranty. Conventional water heaters with tanks deteriorate after years of storing mineral-laden water, but tankless water heaters last mush longer and offer long-term reliability.

The most important component in any tankless water heater is the heat exchanger. Warranties on heat exchanger may run from about 5 to 12 years.