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Directory:Tankless Water Heaters

Lasted edited by Andrew Munsey, updated on June 15, 2016 at 12:47 am.

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What is a Tankless Water Heater?

Tankless water heaters are home appliances used to heat water for residential or commercial use. Also known as 'on demand' and 'instant' water heaters, tankless are designed to heat the water as the water flows through. Unlike conventional tank water heaters, tankless do not have any type of storage tank. Tankless water heaters come in natural gas, propane, and electric models. Tankless water heaters can be broken down into two categories 'full on/full off' and 'graduated'. Full on/full off units do not change the power output at all. The unit is either on or off. Graduated tankless water heaters base the power output on the flow of water running through the unit. This is usually done through the use of a 'flow switch' and means that you will receive the same output temperature of water at .5 gallons per minute (gpm) as you will at 3.0 gpm.

Because energy is not required to maintain a tank of water at a high temperature, the net energy savings can be substantial on site. However, if enough people implement this practice in a city, it creates a peak electricity problem that can end up wasting more energy than is being saved.


Only heats the water as you need it, so there is no need to maintain a tank of hot water during all those times when it is not needed.

Purported to cut water-heating bills by 60%, giving a 10 - 18-month payback time, depending on the vendor.


If enough people implement this practice in a municipality, it creates a peak electricity problem that can end up wasting more energy than is being saved.

In the News

Tankless Water Heaters are Brutal on the Grid When Popularized - Tankless water heaters draw energy on demand, and do not have a thermal energy storage facet. Multiplied by many customers' hot-water usage patterns, these surges of energy amount to a significantly higher peak load for utilities, resulting in increased costs and, more significantly, in increased waste during non-peak times. (PESN Oct. 18, 2005)

Company Develops Microwave-powered Water Heater - MK4, a microwave-powered on-demand water heater. See comments about microwave inefficiency and peak metering. (Slashdot Nov. 25, 2005)

Sites/Pages about Tankless Water Heaters

Consumers Reports on Tankless Water Heaters - They're efficient but not necessarily economical.

Tankless Water Heater Titan Tankless Water Heaters

Tankless Water Heaters (

Tankless Water Heaters listing at Wikipedia


Tankless Water Heaters

Krystal Planet

See also

Conservation - index at

Directory:Home Generation:Hot Water

- Directory

- Main Page

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