Tankless Water Heaters Review Buying Guide

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Tankless water heaters buying tips, review of the advantages, disadvantages, types and popular manufacturers.

Also called on-demand water heaters they are using an innovative tank-less technology to provide hot water on demand and when needed.


Tankless Gas Water Heaters Advantages

tankless water heater by RinnaiTankless water heaters have many advantages over standard storage tank type.

Tankless heaters heat the water on demand while conventional tank type heats the water all the time, even when you are on a vacation. Therefore, hot water is always clean and fresh and no more fighting the rust and scale buildup inside the tank.

Tankless hot water heaters provide an endless supply of hot water with the continuous flow, while keeping the energy consumption and greenhouse gases low. No shortage of hot water is especially important if you have a large family or planning to fill up a hot tub.

Tankless gas water heaters are versatile units; they can be used indoor or outdoor, and due to its compact and small size, they are usually mounted on the wall without occupying the valuable floor space.

These on-demand heaters are able almost completely to eliminate standby heat losses while reducing energy consumption up to 30% (some manufacturers claim saving even more).

Most of the modern tankless water heaters such as Noritz, Rinnai or Navien are using superb features and quality elements for water heating. This includes commercial grade elements, sophisticated electronically controlled processes with self diagnostic programs for easy troubleshooting.

Most of the components can be replaced, so if one element fails you can replace it. They are long lasting - they can last up to 20 years.

There are some comments that tankless water heaters cannot meet the requirements for higher hot water demand, and that they are built for point of use applications only. I disagree with this statement as some models can deliver up to 11 GPM and use multi system connection for even more power and capacity.

Small size and flexible installation are what allows tankless water heaters to be installed virtually anywhere. Keep in mind that proper location is very important for installation as it should be approachable for cleaning, maintenance and flushing, for example.


Common complaints found for tankless hot water heaters are "cold-water sandwiches" where some models are not capable of providing the consistent water temperature. Another drawback is if you need a trickle of hot water for shaving or hand washing, a burner might not ignite as the flow switch doesn't react on the low water flow.

Initial costs of the tankless gas water heater, installation, venting, maintenance and service are much higher than for conventional WH. They are called "Instantaneous" but they do not deliver hot water instant as there is still unheated water between the heating unit and the plumbing fixture.

Tankless electric heaters require lots of Amps so proper panel size should be installed, which is another cost for you.


Tankless water heaters can be found as electric - or gas-powered. Tankless gas water heaters are most of the time factory set to use natural gas, and the conversion kit is used to convert them to use propane or LP gas.

Both gas and electric tankless WH are designed for the whole house or as the point-of-use units. More BTUs (kW) or water flow rate one unit has, more plumbing fixtures can operate at the same time and deliver hot water at the uniform temperature.

Another category of tankless gas water heaters is becoming very popular; gas condensing WH. Condensing technology allows these units to achieve extremely high efficiency, up to 96%, so only 4% of energy is wasted. Typical examples are Rinnai, Noritz and Navien.

Indoor tankless models are mainly combustion sealed so they can be installed even in the kitchen or room.


Tankless water heaters are popular in US and Canada while in Europe they are known as combi or combination boilers (they heat home and water at the same time). Below is the list of popular manufacturers, including the best non-condensing tankless models:

American AO Smith Bosch
Bradford White John Woods
Noritz Paloma Rheem
Richmond Rinnai Ruud
State Stiebel Eltron Takagi
Titan Vaillant

Buying Guide - What to look for

  • Brand (Rinnai, Noritz, Rheem, AO Smith, Bosch, Paloma...) any preference?

  • Fuel type. Tankless water heaters are using mainly natural gas, propane or electricity to heat the water. If the propane gas is your only option the outdoor propane gas tank and its supply lines should be also considered. The advantage of electric tankless water heaters is that the electricity is available everywhere.

  • Size / Capacity. Calculate what the peak hour demand for your household is. Based on how much gallons of hot water your home needs, look for the models that meet this requirement with the water flow rate; usually shown in GPM or gallons per minute. Another important factor to consider is the heating power (BTU for gas units and kW for electric). If the size is not properly optimized you might have only a lukewarm water when several plumbing fixtures are in use.

  • Efficiency. It is easy to buy high efficient heaters. Just look for the Energy Star logo. Energy efficiency, energy factor or EF are actually showing the ratio of the heating energy delivered as hot water compared with the energy that is used by the heater over one day period. Energy Star approved models meet the strict energy efficiency guidelines set by the Government Energy Departments.

  • Venting options.

  • Price and warranty.

See the reviews and prices on Amazon.com.


Tankless water heaters are the great option for homeowners. If you are looking for on-demand heater with low or high water demand, you can find one. Tankless do require a large up-front investment, but you can take advantage when buying the Energy Star model which pays off on the long run.

Tankless water heaters reduce energy consumption at least 30% and heat the water only when you needed, so water is always fresh (vs. storage tanks where it is sitting for hours or days).

Proper sizing will bring you enough hot water, and you will never run out during heavy usage.

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