Top 6 Best Gas tankless water heater 2021

It’s super essential to pick the right water heater for your household’s particular needs to get the full range of benefits. The selection of options on the market is vast, and having an insufficient device for your needs or overpaying for the one you won’t make full use of is all too convenient. In particular, since gas units enable you to install proper ventilation ports and fuel hookups, this equipment can be expensive. The first time, this guide will assist you in getting it right.

A gas tankless water heater will help you save an average of $108 a year in energy costs, for instance. They do conserve more, of course, than their tank counterparts. You would end up saving a lot more if you were to choose from the best gas tankless water heaters out there, mainly if you use them economically.

Tankless gas water heaters last longer than tank heaters, provide hot water whenever you want it on-demand, for as long as you want it, and each month will save you a nice bit of cash. Most reviewers’ record decreases in their energy bills of 30-40 percent! Centered on their convenience alone, these devices are a worthwhile investment. Gas tankless water heaters have improved cold-weather performance and average lower fuel costs over time than electric versions. In the long run, they’re much more effective.

We have sorted some Gas tankless water heaters into simple categories: bestsellers, the highest overall quality, and sales with the highest value.

Image Name Prize Details Price
5.711 GASLAND BS158 Portable Gas Water Heater Best seller Flow Rate: 1.58GPM
Suitable place: outdoor installation
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3.611 Rinnai V53DeP RV53DeP Best Premium high quality Heater Flow Rate:5.3 GPM

Suitable place:
Outdoor Installation Only
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pr6 Rinnai RUC98iN Ultra Series Best Value Natural Gas Flow Rate: Up to 0.96 Energy Factor

Suitable place:
indoor Installation Only
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2.3 Rheem RTG-70XLP-1 Tankless Water Heater, Grey
Best Budget Flow Rate: Less than .45 GPM

Suitable place: outdoor installation
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tankless water heater
Budget friendly Flow Rate: 3.7 GPM

Suitable place: Indoor wall-hung
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1. GASLAND Outdoors BS158 1.58GPM 6L Portable Gas Water Heater

The most competent tankless water heater manufacturer the compact size and lightweight construction of the Gasland BS158 1.58GPM 6L outdoor portable tankless water heater allows for easy transport. Flame failure system, anti-freezing protection, overheating protection will ensure the family safety. 41,000BTU/Hr maximum power output, start-up of low water pressure, only need 2.5 PSI of water pressure. The best outdoor hot water solution, ideal for camping, RV life, or hot water anywhere you need it.

GASLAND Outdoors BS158

Key Features:

  • Flame failure device
  • Anti-freezing protection
  • 2.5 PSI of water pressure
  • Maximum power output 41,000BTU/Hr

This unit reduces the water pressure automatically from 2.5-110PSI. The anti-freezing drain plug can discharge the residual water to prevent freezing in cold areas or in case of no use for a long time. It gives high protection against water temperatures above 167 °F. Automatically shut off the gas supply under unexpected flameouts. This water heater with tankless Gas is designed for outdoor use. To ensure protection, it is recommended that you use it in a well-ventilated environment. For your reference, the dimension is approximately 11.8 x 6.1 x 17.3 inches. It is the best tankless gas water heater for large homes.


41,000BTU/Hr maximum power output, get instant, endless hot water quickly wherever you are. Before using a tankless water heater, there is no need to preheat. The water flows at your ideal temperature as soon as you turn the tap ON. Starting with low water pressure, you only need 2.5 PSI of water pressure. 1.58 gallons of on-demand hot water per minute. The heat and water flow are entirely adjustable.


Its design is very compact size and lightweight for convenience. When you camp, on the beach, etc., it can bring you an excellent hot shower. You can also wash your pets with this tankless outdoor water heater. Hang it on the top/back of the gas water heater using the mounting bracket. It only takes several minutes for you to install it. Or, according to the instructions, you can install it.


This unit saves up to 11.5 percent of technology. The propane water heater exchanger and main burner are designed with advanced combustion technology to reduce gas consumption and burning noise. By using our tankless water heater, you’ll save more.


The flame failure system, anti-freezing protection, and over-heating protection features of this gas tankless water heater guarantee the family’s safety. Reduce the water pressure automatically from 2.5-110PSI. The anti-freezing drain plug may drain the residual water to prevent freezing in cold areas or in case of no use for a long time—high security against water temperatures above 167 °F. Automatically cut off the gas supply under sudden flameouts.

  • Energy Saving
  • Overheating protection
  • CSA Approved Safety
  • Excellent Customer Service
  • Compact Size
  • Outdoor use only

2. Rinnai V53DeP RV53DeP, 5.3 GPM, V53DeP-Propane/5.3

The V53DeP in Rinnai’s propane gas tankless water heater is the ideal combination of high performance, comfort, and value. Compact, easy-to-install, durable, and suitable for outdoor locations, ideal for small to medium-sized homes or remodels; Rinnai products offer peace of mind with promises that exceed the competition. For small areas, V53 models are most suitable.
This water heater has an average efficiency of 0.82 once it’re running. This rating may seem low relative to other brands, but it still manages to be better than other gas water heaters.

Rinnai V53DeP RV53DeP

Key Features:

  • Energy Factor of 0.82 / Uniform Energy Factor of 0.81
  • 15,500 BTU (Minimum) / 120,000 BTU (Maximum)
  • V53DeP HE High-Efficiency Tankless Hot Water Heater
  • Outdoor Installation Only
  • Up to 5.3 GPM hot water flow rate (varies by groundwater temp)
  • Control-R 2.0 mobile app features timers and schedules throughout the day and allows you to put the system into vacation mode remotely.

This best gas tankless water heater provides a reliable source of hot water to multiple fixtures simultaneously in any size home. It only uses energy when hot water is needed. It is an excellent choice for smaller spaces. It fits in crawl spaces and attics without compromising output. It is effortless to install with PVC/CPVC in conjunction with the Ubbink Concentric to Twin Pipe adaptor (other venting options available)
Has a lock function for temperature settings. Prevents unwanted changes to settings

  • Endless hot water for your entire home
  • Residential Factory Warranty – 120 months (heat exchanger), 12 months (labor), 60 months (parts)
  • Compact size
  • Scale control system
  • It uses more amps than are required for a typical 120 amp panel.

3. Rinnai RUC98iN Ultra Series

The Rinnai RUC98iN, which comes with a 4 plus-star ranking, is the first product on our list. It is reportedly a new model from this manufacturer, capable of providing its users with more performance. It is the best whole gas house tankless water heater.
Rinnai Ultra Series Tankless Water Heaters deliver innovation and technical leadership in condensing tankless water heating concept. Rinnai offers ease of installation now with more venting options right out of the box, providing homeowners with an endless supply of hot water, energy savings, a space-saving design, and environmental benefits.

Rinnai RUC98iN Ultra Series

Key Features:

  • INDOOR installation only. Fuel Type: NATURAL GAS.
  • Concentric or PVC venting option
  • Up to 0.96 Energy Factor/Up to 0.92 Uniform Energy Factor
  • Ultra-low NOx emissions
  • 199,000 max BTU

As the only manufacturer to deliver concentrated and twin-pipe PVC venting, there is no need for an adaptor to provide you with twice the venting options for each installation. This best gas tankless water heater provides two options for venting. From one project to the next, the freedom of choice is yours … right out of the box with the RUC line of Ultra Series Tankless Water Heaters.

  • Energy Factor

It features up to 0.96 Energy Factor and up to 0.92 Uniform Energy Factor. The commodity reportedly has ultra-low emissions of NOx and is capable of up to 199,000 BTU.

  • Sleek Design

This tankless water heater has a sleek build with a metallic finish when it comes to appearance. For appliances that have the same silver finish, it suits them better. On top of that, its architecture is also space-saving, making it possible to mount the heater indoors.

  • The space-saving design allows Indoor Installation type
  • Ultra-low NOx emissions
  • Up to 0.96 Energy Factor
  • It has a space-saving design
  • 95% Thermal efficiency
  • Concentric exhaust requires additional OEM parts

4. Rheem RTG-70XLP-1 Tankless Water Heater, Grey

Rheem RTG-70XLP-1 is designed for continuous hot water and is a mid-efficiency outdoor tankless water heater. It has a minimum flow rate of .26GPM and a minimum activation flow rate of .40GPM, which are used to ensure that hot water is received even in low demand situations. Ultra-Low NOx burner fulfills rule requirements of safety with low emissions of SCAQMD. Exclusive Guardian Overheat Film Wrap of this unit prevents it from reaching dangerous temperatures. Maintenance notification settings, self-diagnostic system, and EcoNet enabled mobile app feature (additional kit available) are those features that make Rheem RTG tankless water worth buying.

Rheem RTG-70XLP-1

Key Features:

  • Next Generation Burner Technology
  • Low Activation Flow Rate – Less than .45 GPM
  • UMC-117 remote control and 10ft of thermostat wire is included
  • Exclusive! Guardian OFW overheat film wrap
  • All Rheem tankless models are third-party efficiency certified by GAMA
  • Continuous hot water, energy saving and compact space saving design

Digital remote control and 10ft. Of the thermostat, the wire is some additional features of this unit. As this unit is made for outdoors so, there is no need for venting. It is best if used with up to 3 bathrooms. But one downside of this unit is professional installation; otherwise, the warranty void.

  • What makes this item more reliable?

The 40% thicker heat exchanger of this new RTG-70XLP-1 and a new burner pattern make this unit more durable and efficient. Water-saving mode is the main and additional feature of this unit, making it more reliable and efficient. This feature makes this unit one of the top the best tankless water heater.

  • Is this item Energy-Efficient?

Its stainless steel condensing heat exchanger enables this unit up to 94% energy efficient. Intelligent electronic controls are used to make it more energy-efficient and safe to use. Its concise size encourages space-saving.

  • Easy To Install

It is effortless to install because of 1/2″ Propane line compatibility on every model. It comes along with a Pre-Wired Controller. Maintenance Notice Setting alerts are generated for the homeowner by flashing a warning code to call for a service check. It is the best tankless water heater in the market.

Plus Features

  • EZ-Link cable available for high demand applications to connect two tankless units to operate as one
  • Manifold up to 6 Units with an Optional MIC-6 manifold control board
  • Exclusive! All Rheem models can be linked in up to 20 unit manifold installations by using the optional MIC-180 and MICS-180 manifold control assembly
  • High-altitude capability-up to 9,840 ft. elevation above sea level (no chip required)
  • Intelligent electronic controls designed to increase energy efficiency and safety
  • Self-diagnostic program
  • The digital display shows temperature setting and maintenance codes
  • Built-in electric blower
  • Supplied with a 120-volt power cord
  • Environmentally friendly Low NOx burner meets SCAWMD rule 1146 requirements
  • Freeze protection to -30 degrees F
  • Water-saving mode
  • Maintenance mode
  • Coldwater sandwich problem when recirculation pump isn’t used


For a great shower, Marey GA14CSANG 100,000 BTUs can provide up to 3.7 GPM of full home indoor solution for 3 points of use. This unit is suitable for any house, apartment, cabin, and small commercial use of any scale. For the US and Canada markets, the unit is CSA tested and approved. It is no doubt one of the best natural gas tankless water heaters. It is the best natural gas tankless hot water heater in the market.


Key Features:

  • Freeze Protection
  • Digital Display
  • Overheat Protection
  • UL listed
  • DOE
  • Activates automatically on water pressure between 15-150 PSI
  • Temperature range 95° to 140°
  • Installation type: Indoor wall-hung
  • Requires a 120 VAC and 60 Hz power

This best tankless natural gas water heater unit is designed to use a 100,000 BTU/hr maximum gas input rating and has an impressive maximum flow rate of 3.7 GPM (gallons per minute). This machine is capable of simultaneously serving several points of use. With upgraded components and state of the art circuitry, it is full of features.
There is no pilot light in the device, and when the heater is not used, it does not absorb Gas. To ensure safety, it comes with an anti-freeze system and an over-temperature control thermostat. It meets the specifications of the DOE and has a 0.83 Energy Factor rating.

  • Includes convenient H2O SAVER TECHNOLOGY
  • It comes with a 5-year warranty
  • CSA Certified
  • Digital temperature display
  • Must be installed by a professional plumber or electrician to ensure safety and quality
  • Indoor installation only

6. Rinnai RUS75eN RRUS75eN, White

This Ultra condensing tankless water heater from Rinnai is primarily built for medium-to-large-sized homes; the improved performance of a condensing unit offers extra savings while still providing all the advantages of a regular tankless water heater.
This unit’s remarkable condensing architecture integrates two innovative heat exchangers to achieve maximum heating value from every cubic foot of natural Gas or propane. The stainless steel device recovers residual heat from flue gases to the incoming groundwater preheat, circulating to copper’s primary heat exchanger.

Rinnai RUS75eN RRUS75eN

Key Features:

  • ENERGY STAR® Qualified – Energy Factor up to .93
  • Stylish white cabinet and matching cover panel
  • Quiet Operation: RUS75 @ 55dB
  • High Altitude Approved up to 5,400 feet
  • Ultra Low NOx Compliant
  • Mobile Home Certified
  • Fuel conversion kits available

With the RUS75eN, one of Rinnai’s Super-High Performance condensing tankless water heaters, enjoy the endless supply of hot water. The natural gas RUS75eN model is compact, simple to mount and ideal for outdoor locations, just the small suitcase’s size.
This unit’s control-R 2.0 mobile app features timers and schedules throughout the day and allows you to put the system into vacation mode remotely. It comes with the Residential Factory Warranty – 120 months (heat exchanger), 12 months (labor), 60 months (parts).

Plus Features

  • The RUS75e, with a maximum of 160,000 BTU, is capable of delivering 7.5 GPM of continuous hot water
  • Built-in status monitor; easily upgradable to MC-91-2 controller for remote operation
  • Temperature Range of 120°F – 140°F, with four convenient pre-set temperatures
  • Built-in freeze protection down to -22°F for indoor models and -4°F for outdoor models (gas/electricity required)
  • RUS75eN SE Super High-Efficiency Tankless Hot Water Heater – Natural Gas: Outdoor Installation Only
  • Residential Factory Warranty – 120 months (heat exchanger), 12 months (labor), 60 months (parts)
  • best rated gas tankless water heater
  • Concentric exhaust requires additional OEM parts

Buying Guidelines of Gas Tankless water Heater


Since the tankless water heater is operated primarily by Gas, for protection, the natural Gas it uses must be vented outside. If it is installed outside, there’s no need to get vent kits, but you need to install venting kits and the system if it needs to be installed inside. Make sure what inch of pipe the venting needs and how it should be mounted before purchasing.

Range of Temperature

Tankless water heaters with regular whole house gas reach up to 140 degrees F, ideal for residential use, of course. But if you need to make industrial use of it, then there should be a far wider temperature range than that.

Household Size

Generally, as a five-bedroom home, an apartment does not need the same gallons per minute (GPM) output from its water heater. If you only run one shower or hot water-driven appliance at a time, there is no need to spend a lot of cash for something that is built to run many.

Installation Cost

A cost that you would have to pay for the installation of venting and retrofitting your gas line. There is a higher initial expense of tankless gas water heaters than their electric counterparts. That’s because it is important to vent indoor units, and outdoor units cost much more to be weatherproofed.


A highly energy-efficient tankless water heater will minimize consumption costs significantly, thereby saving your heating bills a lot of money. But suppose you have a low computer in energy efficiency. In that case, it ensures that a significant amount of natural Gas is lost and more greenhouse gases are emitted to pollute the atmosphere. The best energy-efficient tankless water heaters are considered to have thermal efficiency above 0.9

Read About Best Propane Tankless water Heater OR Over all Top Best Tankless water heaters

Frequently Asked Questions

1. Can we use tankless water heaters for commercial applications?

Gas tankless water heaters have proved to be the best choice in commercial and residential applications. Cost reductions, energy savings, and reliability are good. On-demand, they produce hot water, making it a fantastic choice and extremely useful.

2. Does water quality play a vital role in commercial applications?
Water quality is essential in commercial applications. As much as you want to save on costs with a local water source, the water must contain vital minerals such as manganese, magnesium, and calcium. Compared to its counterpart, the tankless water heaters need better water.

3. Benefits of Gas Tankless Water Heater
Gas water heaters are easy to install. They are also cheaper compared to their counterpart’s electric tankless heaters. They are good at recovery after heating large amounts of water.

4. What is the life span of a gas tankless water heater?
A gas heater’s life span depends on a person, but the heater’s actual life is approximately 15 years. Any factors contribute to a gas heater’s life expectancy. They include the efficiency of the machinery and how well the furnace is maintained. By routine servicing of the unit, the useful life of any mechanical equipment is extended.

5.Do gas tankless water heaters work appropriately in cold weather?
You need to round up by as much as 75-100 percent in colder climates where your unit will have to work harder to heat your water. That’s because most models are performed in certain far northern or high altitude regions at average input temperatures, which do not apply.

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