What if the house does not have a centralized supply of hot water, which is so needed? The answer is simple: choose and install the best tankless gas water heater. Such devices are regarded as some kind of heat exchangers.

The water does not heat up in advance; it receives heat only when passing through the required element. Each tankless unit begins to function at the time of water pressure increasing when the tap is opened. The heated water flow is fed into the pipeline and the combustion products are removed using a ventilation system. In old houses with too low water pressure in the system (less than 2.5 PSI), it is better to install special pumps. With stable water pressure, automatic start-up occurs without problems, and the heating temperature will be maintained more correctly.
If you really want to get a decent unit for seamless work, it’s better to get acquainted with popular natural gas tankless water heater reviews, which show the basic functional peculiarities and are able to line it up about the means.

Tankless Gas Water Heater Review

Rinnai RUC98iN Ultra Series


The Rinnai RUC98iN is equipped with a fully automatic ignition system of the burner. The necessary heating and performance parameters are set via a touchpad on the body frame. Outlet water temperature is reflected on the LED display (it also shows the error symbols when they occur). Its maximum flow rate is 9.8 GPM, and the ceiling temperature is 140 ºF that is enough for everyday usage. Pay attention that in the case of groundwater, temperature reaches nearly 50 ºF, the system will have limits – 5-6 GMP. The unit can work for two bathrooms, but it’s better to take care of a good water softener. It’s possible only indoor installation. The official warranty timescales are the following: 12 years for heat exchanger, 5 years for parts, and 1 year for labor. Don’t forget that this device works only with the natural gas, propane is not permissible.


  • There’s no noise while Rinnai gas tankless water heater running.
  • The isolation valves and pressure relief valve are included in the set together with the heater, so there’s no necessity in adaptor purchasing.


  • It needs to wait for 15 seconds to get really hot water.
  • Sometimes there appear different error codes on the display and I have to reset the unit to make it work normally again.

Video Rinnai RUC98iN Ultra Series

Rinnai V75iN


The Rinnai V75iN can provide up to 7.5 gallons of hot water per minute but only if the water is startling a mean temperature. There’s a special Control-R 2.0 mobile app that is suitable for scheduling the work and even setting the unit into vacation mode. It can be used for various water sources and allows taking a shower, making a laundry, and running a dishwasher at the same time. The temperature range is quite wide (98ºF – 140ºF), so the person is able to enjoy really hot water. There’s even a special temperature lock that averts unintentional changes in the set temperature of the water. The factory warranty has different time limits: heat exchanger (10 years), parts (5 years), and labor (1 year). Perhaps, this unit can be regarded as the best gas tankless water heater, but it’s possible to install it only indoors.


  • The unit doesn’t affect the water pressure.
  • It’s possible to adjust the temperature via a special touchpad that is placed on the body frame and can be easily controlled.
  • The leak detection stops water supply to the unit in order to reduce the property damage.


  • The heater requires a special vent system installation, but the last one doesn’t come together with the unit, so the user has to purchase the Rinnai Vent kit additionally.
  • There’s noise while heating the water up.

Video Rinnai V75iN



The Rheem tankless gas water heater can be used for 2-3 bathrooms, but it’s better to remember that you need 2-3 seconds more to get hot water comparing to the traditional tank. The unit comes with a thermostat and one gas valve. It can heat the water as low as 45 ºF to 120 – 140 ºF, and even while using a few taps at once the temperature will remain unchanged (as stipulated). The smoke is forced by the built-in fan (heater works on natural gas). It supports automatic electronic power modulation for stable maintenance of the set temperature. The safety system protects against gas leakage, controls traction, and prevents start-up without water. I can hear some noise while working, but it isn’t annoying or loud. The Rheem RTGH-95DVLN 9.5 GPM has freeze protection (to -30ºF) and can be used outdoor. The warranty period is standard: 12 years for heat exchanger, 5 for the component elements, and 1 year for certain labor.


  • A self-diagnostic system makes it possible to perform all the adjustments without the user’s interference.
  • The special digital display reflects the data on maintenance codes and actual temperature.
  • It possible to unite two heaters in one via EZ-Link cable.


  • It takes 1.8 minutes to get hot water, so I have to turn the tap on and wait.
  • This water heater won’t perform its task during a power outage.

Video Rheem RTGH-95DVLN



This outdoor tankless gas water heater is supplemented with anti-freezing and overheating protection, moreover, the system automatically decreases water pressure amid 2.5-110 PSI. If the pressure falls lower than the 2.5 PSI, the heater won’t be able to ignite. Pay attention that only liquid propane can be used as a fuel. The source water temperature should be higher than the 32°F, otherwise, the user has to drain out the water to elude internal damage of the construction. It’s better to insert 2 “D” cell batteries, plumb in the gas inlet to the supplied gas regulator, connect water inlet with a shower hose, and adjust the required water temperature. Perhaps, the GASLAND Outdoors BE158 1.58GPM 6L isn’t the best gas tankless hot water heater for outdoor usage, but this unit works stable, without noise, and weighs only 15.5 pounds.


  • It’s suitable for both indoor (only in the case of flue pipe installation and good ventilation presence) and outdoor usage.
  • If the temperature reaches over 167°F, the system shuts off gas automatically.
  • It supplies 1.58 gallons per minute that is enough for various basic needs (wash the dish, wash the head or pets).


  • It works really loud and rumbles when is turned on full blast.
  • The manufacturer provides the unit only with a 1-year warranty, which is a short term.

Takagi T-H3-DV-N


The manufacturer accompanies its product with the following warranty time limits: heat exchanger (10 years), parts (5 years), and labor (1 year). Its maximum flow rate is 10 GPM and the temperature level is limited to the 140ºF, which is enough to enjoy really hot water and regulate it according to the personal preferences. The unit’s sound level is only 55dB, so its working process doesn’t create serious noise. It has a self-diagnostic feature that helps find out the problem and find its reason in the manual (there are some recommendations on solving the most widespread and unserious problems). This device uses the 3/4 natural gas pipe for 200.000 BTUs and its length can be only 15ft max. Pay attention that the conversion of the natural gas to propane will rescind a warranty.


  • This Takagi tankless gas water heater is able to produce hot water for 4 bathrooms (in a warm climate).
  • It can be used in indoor conditions.
  • If you will trigger the heater and turn the water off, the standby mode will functionalize for 35 seconds that is useful for quick washing.


  • If you have a natural gas well, you have to additionally install the inline filter to seamlessly use the device.
  • The water temperature drops by a few degrees at the time of heavy use.

Video Takagi T-H3-DV-N

Eccotemp i12-NG


The i12-NG is fully automated. There’s no pilot light, but the LED display on the front panel reflects all the important information. At a flow of 3 GPM, the heater raises the temperature to 38 ºF, and at 1.5 GPM this level will reach the 77 ºF. Pay attention that this heater works only on natural gas, switching to propane is prohibited by the manufacturer. The vent size is 3” and the venting can be installed only in a horizontal position. The Eccotemp i12-NG probably can’t be called the best tankless gas water heater, as it’s not suitable for cold climate and can freeze from time to time. Moreover, the minimum gas rate reaches the 25.000 BTUs, so the possible owner has to create becoming conditions for the heater’s usage. Pay attention that this device is complemented with a 10-year warranty on heat exchanger and a 5-year warranty on elements.


  • The unit is suitable only for indoor usage, but in a case of installation in a warm and dry climate, the outdoor placement is possible.
  • There’s no need to reset the unit after the loss of power, it continues to work without interruption.
  • The Eccotemp i12-NG can deliver two outflows at a time, so it may be suitable for two bathrooms or one bathroom and one kitchen tap.


  • The cooling metal cracks after shutdown.
  • A water softener is required for the usage, otherwise, the device won’t work seamlessly.

Video Eccotemp i12-NG

Takagi T-K4-OS-NG


This outdoor natural gas tankless water heater has inbuilt freezing and moisture protection, so it can be installed even in cold regions. It requires 3/4” gas supply and it’s able to work with 1/2”, but the manufacturer recommends using only 3/4”. I really like that the Takagi provides its product with 5 years warranty for heat exchanger, 3 years for parts, and 1 year for labor. Its heat exchanger is made of copper, so it has a resistance to corrosion processes. You can freely choose the heater if the minimum BTUs is at least 19.500, otherwise, the device won’t work properly (the maximum index is 190.000 BTUs). Note that this tankless unit works only with a stainless-steel venting that has to be purchased separately.


  • Its maximum flow rate is 8.0 GPM that allows using the heater for a few sources (2-3 bathrooms).
  • The remote controller TK-RE02 helps adjust the temperature.
  • There’s an air-fuel ratio modulator that monitors the temperature and shuts off the system in a case of overheating.


  • There’s some humming noise that comes out of the fan and stays for a few seconds after shutdown.
  • The remote controller isn’t waterproof and steamy conditions may be harmful to it.

Rheem RTG-95XLN


The Rheem outdoor tankless water heater is supplemented with an internal water filter, which performs its softening (but at the same time, this filter has to be cleaned occasionally). The construction is protected by a metal case that isn’t affected by the high humidity conditions. A waterproof LED display shows the temperature adjusting and error codes. It contains the overheating and freezing defense mechanism, so the device can be used even when the temperature outside is -30Fº. There’s a stainless steel condensing heat exchanger that performs the exhaust heat recycling and allows the system to gather more energy within the combustion process. The minimal flow rate is 0.26GPM. Pay attention that warranty periods are the following: heat exchanger (12 years), parts (5 years), and labor (1 year).


  • The device comes with a UMC-117 remote control that is useful for the working mode adjusting.
  • It produces 9.5 GPM at 35ºF that’s enough for 4 bathrooms medium usage.
  • The electric power supply requirement for this facility is 120VAC/60Hz that allows a few units to connect one circuit.


  • The internal water filter has to be cleaned from time to time.
  • It’s too sensitive to pressure and even a small blow can leave a dent on the body frame.

Buyer’s Guide

Tankless Gas Water Heater: Benefits

  • The main advantage of tankless gas water heaters is the heating method. Unlike an electric one, a gas heater is much cheaper (due to the cost of consumed fuel).
  • Gas economy is not a secret, so if you have a choice of a water heater, it is better not to go for electric models.
  • The device is complemented with a system for controlling the intensity of a flame burning, which minimizes the amount of harmful emissions into the atmosphere.
  • This unit is much easier to clean and repair. It does not deteriorate as quickly as electrical counterparts.
  • The longevity of the device itself is high (the warranty periods of above-mentioned models are the evidence), but at the same time, it directly depends on whether the maintenance and monitoring of the relevant specialists in a timely manner is carried out.
  • There’s a traction control device that monitors the level of temperature indicators. When the temperature rises above normal, the gas valve closes automatically.
  • It has decent cold-weather resistance and is regarded as a reliable unit for long-term usage.
  • Every the best gas tankless water heater (including all the surveyed items) has a special control system that simplifies the user’s adjustment of the main parameters of the device – power, pressure, and temperature.

How to Choose Tankless Gas Water Heater

Size Destination
The heaters are divided into units for:

  • Shower and bathtub (nearly 2.5 GPM).
  • Dishwasher (1.3 GPM).
  • Kitchen sink/or bathroom (2.2 GPM).

When choosing a heater capacity, one should rely on personal requirements, as well as the number of water consumers. If you consume water at several points (washbasin, shower, etc.), give preference to more powerful gas water heaters.

Smoke evacuation
According to the type of combustion products exhaust, the heaters are divided into turbocharged and with natural smoke removal. In turbocharged gas units, there’s an inbuilt fan, which is turned on simultaneously with the ignition of the burner and forcibly pulls the combustion products to the street. In devices with natural gas exhaust, this process occurs due to the draft.

Ignition method
It is better to take semi-automatic devices, as they are equipped with a piezo ignition button. It allows you to ignite the construction yourself. You need to press the button below without making a physical effort. Turning off the ignition occurs for the same principle.

Water pressure and its hardness
When choosing a device, remember the dependence of its operation on the pressure and water hardness (the last one leads to salt deposits in the heat exchanger, which brings to its destruction, so it’s better to use softeners). If the water pressure and gas pressure are too low, it may not turn on, and deliberate operation under low pressure often leads to premature breakage or scale. You can remedy the situation with the help of a special pump, which increases the pressure; otherwise, the heater will not function normally.