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Home > Tankless Water Heaters

Tankless Water Heaters

How Tank-less or On Demand Water Heating system works. Bosch, Noritz, Paloma, Rinnai Tankless Hot Water Heaters Review



When searching for residential tankless water heaters, also called on demand and instant hot water heaters, it is important to know that their tank less system and water heating process is different from tank type systems.



About Tankless Water Heaters

The main advantage of these instantaneous water heaters vs. storage is tank-less design, continuous hot water flow and endless supply, less energy consumption (up to 30-40% when comparing it to water tank heaters), therefore more savings for you and no worry about running out of hot water during showers.

Comparing tankless water heaters with storage water heaters that are heating water even when you are away or not using it, tankless hot water heaters work only when you open the hot water tap.

tankless water heatersOn demand water heaters can use gas or electricity. My favorite types are tankless gas water heaters with the electronic ignition. You can also find water heaters with the continuously burning pilot light, both models with pros and cons.

The size of the instant water heaters you need depends on demand, how big your house is and the family size. Some manufacturers offer a multi-system set-up that can link many water heaters into one system, to satisfy demand even for the largest houses.


Majority of these units are whole house tankless hot water heaters, as they have higher GPM flow rate capacity, so they handle demand for more than one application at a time.

There are also some manufacturers that offer economic residential and commercial grade combi boilers or hot water heaters to be used for space heating and water heating at the same time.

Check out the lowest prices on tankless hot water heaters here.


How Tankless Water Heaters Work

There are some tankless heaters where heating element is controlled by the flow-sensing device that operates with a constant heat input and maximum flow rate. Flow rate depends on the water pressure which can be adjusted on the knob.

If there is a request for maximum water flow, the outgoing water toward the hot water tap is cooler since it spends less time passing through the heat exchanger.

Modern tankless models are using the latest technology where the output temperature, water flow, safety and other parameters are controlled and regulated by the electronic circuit board.

how tankless hot water heaters work

When you open the hot water tap a water flow sensor in the tankless hot water heater sends the signal to the electronic module. From there signal goes to the gas valve to open the gas flow.

If all the requirements are met, natural gas or propane flows into the burner located inside the combustion chamber. The gas is ignited either by the pilot flame or spark from the electrode.

Burning gas heats the heat exchanger where incoming cold water is quickly heated to the pre set and desired temperature. The heat exchanger transfers the heat from the burner to the water heating instantaneously. A vent pipe vents products of combustion out using the direct vent or powered vent system.

Once the hot water faucet is turned off, the water flow stops and flame goes out. As it can be seen from the above explanation tankless water heaters heat the water on demand, while providing you with an endless supply of hot water. You can see them often installed on the wall.

Tankless Water Heaters Reviews by fuel source


Electric tankless hot water heaters have a compact design, saving you lots of space. They have a long service life as they are less prone to hard water and sediments. You can choose point-of-use or whole-house water heaters. Electric tankless water heaters don't produce greenhouse gases. Top selling brands in North America are Bosch PowerStar, Titan, Stiebel and Eemax. Best deals of electric tankless heaters are found on Amazon.com.

Gas tankless hot water heaters are environmental friendly appliances also. Many of them utilize advanced technology for energy efficiency, and meet strict emission standards. They can use natural gas or propane - LP. Gas tankless water heaters produce higher flow rates than electric ones.

Best deals of gas tankless heaters are found on Amazon.com.


Tankless hot water heaters can be further divided into two categories; one that can only work as on/off and the other with modulation.

Instantaneous water heaters with modulation, base the heat output on the water flow. For example if the demand for hot water is higher, modulating gas valve provides more gas and the final result is more power.


Tankless Water heaters manufacturers


Here is the list of the popular residential tankless hot water heaters brands where many of them are Energy Star qualified models, some brands are cheap and the other expensive:

  • Rinnai tankless water heater
  • Noritz tankless hot water heater
  • Paloma tankless
  • Rheem tankless water heater
  • Takagi on demand water heater
  • Bosch tankless
  • A O Smith water heaters
  • American water heaters
  • GE water heaters
  • Stiebel Eltron electric tankless hot water heaters

What is the cost of your favorite tankless model, check out prices here.


On demand Water Heaters Reviews - Benefits

  • Endless hot water supply. Run out of water? Never.
  • Durability, life span is 20 years or more (for some).
  • You can save up to 50% of energy and water heating costs.
  • High efficiency water heaters available, marked as Energy star.
  • Flexible installation options, can be installed anywhere, inside or outside.
  • All the parts are replaceable.
  • Lower greenhouse gas emissions.
  • Reliability rating is 99%.
  • Safety - no scalding injuries.
  • Provides you clean and fresh hot water.
  • No tank no leaking problems.
  • Some use smart technology with self-diagnostic program (great for repairs) and precise temperature control for safety and comfort.
  • Government tax credit, rebate and other incentives.
  • They can use natural gas or propane (LP).

Tankless hot Water Heaters Reviews - Disadvantages

  • With the up-front costs tankless system can cost up to three times as much as water tank heaters.
  • Required upgrades like venting system or gas line are costly.
  • Your hot water output is split among all your household fixtures, the reason why an inconsistent water temperature occurs.
  • Venting gas and propane units requires expensive stainless steel tubing, for some brands other materials are used.
  • Electric instant water heaters may require an additional circuit and lots of energy.
  • Gas water heaters require the additional expense of an annual servicing.
  • Instant water heaters need a minimum flow rate to activate the heat exchanger.
  • Impossible to include renewable energy technology in tankless water heating system.
  • Tankless water heaters are reliant on the water pressure that is delivered to your home, you need good plumbing system.

Related Articles about Tank-less / On Demand water heaters


Tankless hot water heater price is one of the major factors when searching and selecting the right on demand hot water heating system. Compare the costs of Rheem, Bosch, Takagi, Noritz, Paloma, Rinnai and other.

American Tankless Hot Water Heater - Review of On Demand Natural Gas and Propane Water Heaters from American Water Heater Company.

Bosch Tankless Water Heating - About on demand water heating systems from German water heaters manufacturer Bosch and popular Aquastar and Powerstar models.

Noritz Water Heater - Reviews of Tankless Gas Hot Water Heating Appliances from Japanese manufacturer Noritz. Noritz America; Benefits, Main Features and Gas Model Review.

Paloma Water Heater - Reviews of Tankless Gas Hot Water Heating Appliances from Japanese manufacturer Paloma. Benefits, Main Features and Gas Model Review.

Rheem On Demand Water Heaters - About on demand water heating systems from water heaters manufacturer Rheem; Direct vent, Power vent, Energy Star models.

Rinnai On Demand Water Heaters - Top rated Energy Efficient and Energy Star Rinnai hot water heating systems. Reviews of the popular Rinnai Water Heaters using natural and propane gas.

Compare Tankless Hot Water Heater - Top Gas Water Heater Comparison
Bosch Aquastar, Rinnai vs. Noritz, Rheem Gas Tankless Water Heater Comparison and Top features Review.

Tankless Hot Water Heater Parts - Review of Tankless Water Heater Elements; Thermocouple, Pilot Light, Heat Exchanger, Venting.

Sizing a Tankless Water Heater - Selecting the Best Tankless Products for Water Heating based on the size. How to Calculate the Size of On Demand Water Heaters.

Tankless Heater Manufacturer Listing - Gas and Electric Boiler and Tankless Heater Brands: Bosch, Rheem, AO Smith, Rinnai, Noritz, Vaillant...

Best Titan Tankless and Electric Water Heater - Find the detail review about the top selling Titan SCR2 electric and tankless model from Niagara Industries.

Water Heater Tax Credit - How to get $1500 tax break on Energy Star tankless water heaters, as the government tax incentives.

Electric Tank-less Water Heater Reviews - Find review of the popular electric tankless water heaters; PowerStar, Tempra, Titan and Eemax.

How to winterize Tankless Water Heater to avoid your tankless water heater freezing and braking during the winter cold days.

Eemax Tankless Water Heaters - Find detail review of Eemax Water Heaters for point of use and whole house water heating.

Installing a Tankless Water Heater - Step by step guide how to install a tankless water heater; Noritz, Paloma, Rinnai and other.

Review of Rheem Richmond tankless water heaters, features and models.

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