The gas tankless water heaters have transformed the way homeowners get access to hot water by offering an on-demand heating system that is not restricted by the capacity of a tank. These units are efficient in that they only heat the water when required and this removes standby energy losses and gives unlimited hot water.
When you are planning to upgrade your current system or install a new water heater, the selection of the gas tankless model can make a great difference in the efficiency and comfort level of your home.
This ultimate guide will compare the best gas tankless water heaters available in the market, their flow rates, BTU rating, installation requirements and special features.
Whether it is a whole-house system that can serve several fixtures at a time or a small unit that is ideal to serve a small household, we have chosen models that are the best in terms of performance, reliability, and price.
| Model | Flow Rate | BTU Rating | Installation | Best For |
|---|---|---|---|---|
| Rinnai RX199iN | 11.1 GPM | 199,000 BTU | Indoor/Outdoor | Large homes with multiple fixtures |
| Rheem RTG-95DVLN-3 | 9.5 GPM | High Efficiency | Indoor | Medium to large households |
| FOGATTI Comfort 180S | 8.1 GPM | 180,000 BTU | Outdoor | Multi-fixture homes needing outdoor installation |
| ThermoMate | 4.7 GPM | 102,000 BTU | Indoor | Medium-sized households |
| Ranein | 3.6 GPM | 80,000 BTU | Indoor | Small households or point-of-use applications |
#1 Rinnai RX199iN Condensing Smart Sense Gas Tankless Water Heater
The Rinnai RX199iN is the best gas tankless water heater that is available in the market and it has been designed to provide the best performance to large households that consume a lot of hot water. This powerhouse unit provides a powerful 11.1 gallons per minute (GPM), which is sufficient to serve up to seven fixtures at once without experiencing any change in temperature or pressure.
This model ensures that there is constant supply of hot water in your house when there are several showers, dishwashers or washing machines in use.
The RX199iN is one of the most versatile models on the market with Rinnai Smart Sense gas control system that can be used with either natural gas or propane, so you do not need to buy a particular model depending on the type of fuel you use. The Versa Vent technology of the unit gives you the flexibility of installation both indoors and outdoors depending on the configuration of your house and space limitation.
Although it has a strong 199,000 BTU capacity, this unit has an impressive 0.98 UEF (Uniform Energy Factor) that makes it one of the most efficient gas tankless water heaters in the market.
This super-high efficiency rating means less utility bills and less environmental impact. The condensing technology recovers more heat that would have been wasted on exhaust gases and this maximizes the use of energy.
The interface is easy to use and allows easy adjustments of temperature and monitoring of maintenance, and the Quick Flush feature makes routine maintenance easy to perform to increase the life of the unit. The optional Controlr module, not included with the base unit, allows Wi-Fi connectivity to make temperature adjustments and monitor your system remotely using your smartphone.
The RX199iN is compact in size (roughly the size of a small suitcase) and, therefore, saves space and provides better performance and unlimited hot water as compared to conventional tank systems.
This high-end model is perfect in a bigger house with a high demand of hot water at the same time or in a house where the homeowner never wants to feel the pain of running out of hot water once again.
#2 Rheem RTG-95DVLN-3 High Efficiency Indoor Tankless Water Heater
Rheem RTG-95DVLN-3 is one of the best indoor tankless water heaters that can be characterized by the combination of high performance and energy efficiency. This non-condensing unit has a flow rate of 9.5 GPM which is enough to supply hot water to various hot water needs at the same time and therefore suitable to medium to large families that require hot water in various parts of the house at the same time.
This model of Rheem is specifically designed to be installed indoors and it provides you with a continuous supply of hot water in your home even at the peak time. Be it when you are taking a shower and have the dishwasher running, or when several members of the family need hot water simultaneously, the RTG-95DVLN-3 will help you to forget about the inconvenience of running out of hot water in the middle of the shower or having to plan the use of hot water among family members.
The unique feature of this model is that it saves water. The new water-saving mode has the capacity to save up to 1,100 gallons of water per year, which is a great environmental advantage that also means reduced water bills.
This aspect is particularly useful in areas where water is rationed or to the eco-friendly homeowner who wants to minimize his or her use of resources.
The high-efficiency design of the unit means that it will only be in use when hot water is requested, and there is no standby heat loss that is associated with the traditional tank systems.
This on-demand heating system will translate to a significant energy savings in your utility bills in the long run especially when you are replacing an old tank-type water heater.
The RTG-95DVLN-3 has installation requirements of proper venting and gas line sizing but once installed correctly it will provide reliable consistent performance with minimal maintenance requirements.
This Rheem model is an outstanding value and performance to households that appreciate efficiency, consistent hot water supply and space-saving advantages of tankless technology.
#3 FOGATTI Natural Gas Tankless Water Heater For Outdoor Installation
The FOGATTI Comfort 180S Series is a superior outdoor tankless water heater that is ideal to the homeowner who requires a high-powered, weatherproof system to serve his or her hot water requirements.
Having a huge flow rate of 8.1 GPM and a heating capacity of 180,000 BTU, this unit can easily serve 3-5 water outlets at a time, and thus it is a perfect choice of family that needs hot water in several places of the house.
Being a serious outdoor unit, the FOGATTI does not require indoor venting and frees up precious interior space. The well-designed construction features a fan installed at the bottom that does not allow the smoke to flow back and makes the combustion stable no matter what the weather is.
This aspect improves safety and durability, and this aspect helps to increase the operational life even under the elements.
The remote control panel that comes with it is one of the most impressive features as it enables one to adjust the indoor temperature without leaving the house and going to the unit.
Such a convenient method implies that you can adjust settings easily at home, not depending on the weather outside.
This model is characterized by temperature consistency, due to the high-tech water servo technology and accuracy temperature sensors. The system monitors and controls the flow of water and the amount of gas to ensure that the temperature is maintained at an impressive +/- 1 degree F of what you set.
This four-stage combustion system will make sure that you will have the same comfortable shower temperature in the cold winter mornings and hot summer evenings.
The outdoor design of the FOGATTI makes it especially suitable in homes that have a small interior space or as a replacement of the current outdoor water heating systems. The gray exterior finish is made to match most home exteriors in an unobtrusive way and is also weatherproof.
The FOGATTI Comfort 180S is an outstanding value and reliable solution to homeowners who want a high-capacity outdoor tankless system that will provide reliable performance throughout the year.
#4 ThermoMate 102,000 BTU Natural Gas Tankless Water Heater
ThermoMate Natural Gas Tankless Water Heater is a very good compromise between efficiency and performance, and it is a good choice of medium-sized households. Having a flow rate of 4.7 GPM and a heating capacity of 102,000 BTU, this indoor unit will be able to comfortably serve 3-4 fixtures at a time, which is sufficient to cover daily needs of a family without any waiting time or temperature changes.
The most outstanding thing about this model is its high-tech temperature stability. The in-built chip regulates the heating power an amazing 20,000 times per second, so the hot water temperature is kept within +/- 1 o F of your desired setting.
This accuracy will ensure that you will have constant temperatures in the shower without the cold or hot spurts that may be experienced in less advanced systems.
The ThermoMate has a heat exchanger made of high quality oxygen-free copper, which has high thermal conductivity and corrosion resistance than stainless steel, which is used in most of the competing models.
The thermal efficiency of this material choice is impressive at 98 percent (compared to about 80 percent with stainless steel models) and the Uniform Energy Factor (UEF) is 0.81. These efficiency ratings equate to about 30 percent reduction in operating costs as compared to the traditional tank systems.
This well-designed unit is full of safety features, such as full protection against boil-dry conditions, freezing, flame-outs, overheating, pipe blockage, excessive air pressure, etc.
This comprehensive safety package offers security and safeguards your investment as well as your home against any possible dangers that may be caused by water heating.
Installation should be done with proper sizing of the gas line and ventilation and once installed, the ThermoMate is maintenance free and delivers reliable on-demand hot water.
The ThermoMate is an excellent value and a solid performer that will satisfy the needs of households that want a combination of performance, efficiency, and high-end safety features in a mid-capacity tankless water heater.
#5 Ranein Natural Gas Tankless Water Heater For Small Households
Ranein Natural Gas Tankless Water Heater is a good starter model that can be used in small homes or where the hot water needs are not very high. This small indoor unit has an 80,000 BTU heating capacity and 3.6 GPM flow rate, which is just right to serve 2-3 water supply points, which is usually enough in apartments, condos, or smaller houses, a bathroom, kitchen, and a bar area.
The Ranein does not have any waiting time to deliver hot water as opposed to the traditional tank water heaters that take a long time to preheat.
This immediate access does away with the common 30-minute reheating time of a tank after it is emptied, so that hot water is always ready when it is wanted, without prior planning or staggering of use.
Among the most convenient functions of this model, there is the four pre-programmed temperature modes that are specific in their use. The Dish mode (100 o F) is the perfect temperature to wash dishes without burning hands and the Fruit mode (95 o F) is a soft cleaning mode to wash produce.
Personally, the Elderly mode (104 o F) is safe and comfortable to use on sensitive skin and the Infant mode (107 o F) is warm enough to bathe the children. These pre-set features make it easy to use and safer to the different members of the household.
The size of this unit is compact and therefore it is ideal in homes that have limited space to install the unit. Being an indoor unit, it needs to be vented, but the small size allows it to be installed in a small utility closet or other small area where a conventional tank would not be feasible.
The Ranein does not have the high flow rates of the more expensive models, but it is narrowly focused to deliver dependable performance in smaller homes or as a point-of-use heater in individual rooms of larger homes.
This is an inexpensive tankless alternative that provides unlimited hot water to singles, couples or small families with minimal hot water requirements without the cost of oversized systems that serve larger families.
Comprehensive Buying Guide For Gas Tankless Water Heaters
Understanding Flow Rate Requirements
The most important specification to note when choosing a gas tankless water heater is possibly the flow rate which is expressed in gallons per minute (GPM). This figure shows the amount of hot water that the unit can generate at the same time. To figure out what your household needs, sum the average GPM needs of the fixtures you may use simultaneously:
- Shower: 1.5-2.5 GPM
- Bathroom faucet: 0.5-1.5 GPM
- Kitchen faucet: 1.0-2.0 GPM
- Dishwasher: 1.0-2.5 GPM
- Washing machine: 1.5-3.0 GPM
To take an example, in case you habitually run a shower (2.0 GPM) and kitchen faucet (1.5 GPM) at the same time, you would require a unit with a minimum of 3.5 GPM. The bigger households that have more than one bathroom will need to look at the models with the higher flow rate of 8-11 GPM to allow simultaneous use without the temperature variation.
BTU Rating And Heating Power
The rating of the tankless unit is in BTU (British Thermal Unit) and this is the heating power. The higher the BTU rating, the more heating capacity and the capacity to accommodate lower incoming water temperature. In northern climates where groundwater temperatures may be much lower, a higher BTU rating is particularly important in order to achieve sufficient flow rates.
The entry level models are usually 80,000-100,000 BTUs, and this is suitable to small families or warmer regions. The mid-range units offer 120,000-150,000 BTUs, which are appropriate in most average-sized houses.
High-end models produce 180,000-199,000 BTUs, which can support the most challenging applications even in the colder areas.
Installation Considerations: Indoor vs. Outdoor
Gas tankless water heaters require proper venting to remove combustion gases safely. When choosing between indoor and outdoor models, consider:
- Indoor: Needs special venting (usually special stainless steel venting materials), clearances around the unit, and may need an upgrade of the gas line. Shields the unit against weather conditions and freezing.
- Outdoor installation: There is no need of complicated venting systems hence saving on installation costs. Needs freeze protection in cold climates and weather-proof building. May require more extended hot water delivery lines that may result in minor delays in the delivery of hot water to fixtures.
Others such as the Rinnai RX199iN are flexible in that they can be installed indoors or outdoors giving you more flexibility depending on the layout and restrictions of your home.
Energy Efficiency And Operating Costs
When comparing models, look at the Uniform Energy Factor (UEF) rating, the higher the rating the more efficient the model. Standard models are usually rated at UEF 0.80-0.85, whereas condensing models can achieve 0.92-0.98, by recovering more heat in the exhaust gases to achieve maximum efficiency.
Although tankless units tend to cost more initially than the traditional tanks, they are more cost effective in the long run due to their longer life span (15-20 years compared to 8-12 years of tank life) and savings of 30-40 percent of water heating expenses.
Condensing units are more expensive to buy but are more efficient and have lower operating costs especially in homes that consume a lot of hot water.
Gas Supply Requirements
Most homeowners do not consider the need to have sufficient gas supply when fitting a tankless water heater. These units need much more gas input than conventional tank water heaters, usually 2-3 times as much, but in shorter periods. Check before you buy:
- Gas meter capacity (is it capable of providing the needed BTUs)
- Gas line size (can be upgraded to 3/4 or even 1″ in length of run and BTU needs)
- Appliance gas pressure (usually 7″ w.c. on natural gas appliances)
Poor gas supply is one of the most frequent reasons of performance issues with tankless systems, which leads to uneven heating or failure to achieve the desired temperatures. Pre-purchase professional evaluation can avoid expensive alterations or dissatisfaction with performance.
Maintenance Requirements
Gas tankless water heaters also need to be maintained regularly especially in hard water areas to ensure maximum performance and life span. It is necessary to descale the heat exchanger annually to get rid of mineral deposits.
This is simplified by some models such as the Rinnai RX199iN that has the Quick Flush feature.
You may want to consider a water softener or scale inhibitor system in the event that your water is very hard as this will greatly increase the life of your tankless unit and keep it efficient. Also, the majority of manufacturers suggest that venting systems, burners, and electronic parts should be checked on a yearly basis to provide safe use.
Advanced Features Worth Considering
Modern gas tankless water heaters offer various features that enhance convenience, safety, and performance:
- Wi-Fi: Enables the temperature to be changed and monitored remotely using smartphone applications
- Recirculation pumps: Decrease the wait time of hot water at far fixtures
- Scale detection: Warns you when it is time to maintain it
- Freeze protection: Necessary where the unit is installed in an unheated area or an outdoor model in a colder climate
- Preset temperature settings: Make it easier to use in various applications such as bathing children, or washing dishes
- Condensate neutralizers: Condensing units need to have a condensate neutralizer to avoid acidic condensate destroying plumbing
Although these features increase the initial price, they can make the user experience much better and safeguard your investment throughout the life of the unit.
Compatibility With Home Size And Climate
Climate is a very important factor that determines the size and type of tankless water heater to be used. In the colder northern areas where the ground water temperature may be as low as 40F in the winter, you will require a more powerful unit with more BTU output to attain the same flow rate as in the warmer southern areas where the incoming water may be 60F or more.
As a rule of thumb, each 10 o F decrease in incoming water temperature will require approximately 1 GPM more capacity to achieve the same performance. Sizing your unit: To be sure that your unit will perform well all year round, use the coldest ground water temperatures in your area.
