Best Gas Tankless Water Heater – Ultimate Consumer Guide

Best Gas Tankless Water Heater

First of all, we want to congratulate you on your decision. You have chosen tankless water heaters over water heaters with the tank. Though I have gathered a lot of information about tankless water heater from If you’re not 100% sure about installing the tankless water heater, then read the best comparison article on Tank vs Tankless Water Heater.

Now, it’s time to choose between electric or gas tankless water heater. Don’t know much about it? No problem, our team is here to help you out. Read “Electric or Gas; which tankless water heater is right for me?”

If gas is the right option, then we have 10 Best Gas Tankless Water Heater for you. Another small matter appears on choosing between Natural Gas or Propane operated tankless water heater.

Not enough information to decide? Again, our team of experts have researched and prepared a comparison between Natural Gas and Propane Hot Water Heater.

What tankless water heater do I need; Propane or Natural Gas?”

Here, we’ll cover 4 important factors to help you decide easily between natural gas and propane.

Best Gas Tankless Water Heater

Main Difference

Though natural gas and propane both are fossil fuels, they have some differences. Natural gas is known as clean energy alternative because it is the clean-burning fuel that produces less harmful emissions than oil or coal.

Propane is called liquefied petroleum gas or LP gas. Propane is considered “green fuel” and natural gas is considered “greenhouse gas”. Greenhouse gases are harmful to the environment where green fuels are not.

Natural gas is safer than propane. When leaked, natural gas dissipates more quickly in the air where propane cannot. In case, if you’re wondering which one is eco-friendlier, they both are eco-friendly. A study shows not much difference they do to have effects on nature.


The full meaning of BTU is British Thermal Unit. BTU is needed to measure fuel consumption of an engine. Propane is measured in gallon but natural gas is measured in the cubic foot. For comparison, we’ll convert propane into the cubic foot.

1 cubic foot of propane is equal to 2516 BTUs and 1 cubic foot of natural gas is equal to 1030 BTUs. Propane has more than twice energy than natural gas.

If you have a gas water heater that burns 140000 BTUs in one hour, then you’ll need 55 cubic foot of propane and 135 cubic foot of natural gas.


We are considering 15$ for natural gas per 1000 cubic feet and 2.4$ for propane per gallon cost.

To create 140000 BTUs, you’ll need 135 cubic foot of natural gas costing 2.025 dollars. To create the same amount of energy, you’ll need 1.53 gallons of propane costing 3.67 dollars. So, natural gas is cheaper than propane.


For using propane, you only need a propane tank. But for natural gas, you have to dig up your yard to get access to the gas line. Once installed, natural gas is less costly than propane.

Once you’ve decided, let’s take a look at a quick comparison table for you. It contains 5 Best Natural Gas Tankless Water Heater and 5 Best Propane Tankless Water Heater.

You can click on the individual product listed above to see the current Price and Offers, and a full review. After countless hours put into research, our experts tell us to consider 7 Major Factors before choosing a gas hot water heater.


We’ve seen how these products perform at various temperature rise. Different states have different incoming water temperature throughout the year. Southern states are generally staying warmer than the Northern states. Considering the lowest temperature in your area will give you the best gas tankless water heaterto get warm water throughout the year.

During analysis, all water heaters’ output temperature was set at 100°F. To make a standard comparison, we set the lowest incoming water temperature at 40°F and the highest at 75°F.

Hot water flow will vary according to the temperature rise. The low temperature will result in the high-temperature rise and low flow rate and vice-versa. The flow rate is measured in GPM which means Gallons Per Minute.

My Need

The requirement varies person to person, home to home. There are several points in a home or office where warm water is needed.

To make a clear comparison, we set a standard of 1 faucet, 1 dishwasher and 1 showerhead. Combinedly, they need 5 GPM for constant use where faucet needs 1 GPM, the dishwasher needs 2 GPM, and showerhead needs 2 GPM.

You can measure the GPM (Gallons Per Minute) by yourself easily. Put a gallon measuring bottle or bowl at the faucet or shower. Then run it for 10 seconds and see the water level.

Now multiply the water level that touches the number of the bottle with 6. Voila! You got the GPM you need. Here, we’ve compared GPM by considering incoming water temperature at 75°F and output temperature of the heater at 100°F.


Before installing a tankless water heater, make sure to follow all the local plumbing codes. Maintain proper spacing and proper venting system for easy troubleshooting in future.

Be careful about warranty conditions because a small alteration during installation may void the warranty. If you are not so sure about installing all by yourself, then call for a professional.

All instant water heaters come with an installation manual. Following the manual, you can easily set up one. But if you don’t have enough tools or confidence, you should not do it. The problem occurred during installation may cause the heater not working at its full capacity.

Also, you may experience “cold water sandwich” effect. It means getting cold water in the middle of a hot shower. And trust me, you don’t want to have that.



You have several options at your hand for venting. The outdoor units don’t need venting. Just a shade over the unit is enough. But for indoor heaters, you need to know all types of venting to choose the option for you.

There is horizontal or vertical, sealed combustion or in-room combustion. Horizontal venting means the ventilation pipe going out through the wall where the unit is mounted. Vertical venting means, the ventilation pipe going out through the roof.

In-room combustion means, the unit will use the intake air from the room where it is mounted. In that case, the room needs to have constant air supply.

Sealed combustion means, the unit has to intake air from the outside of the room it is mounted on doesn’t have enough air. Now, let’s look at the comparison table.


Energy efficiency is a big deal for choosing inline water heater. More energy efficiency means it will save more money on your water heating cost. Storage tank water heaters waste up to 40% of the energy provided. But instant hot water heaters waste a maximum of 21% energy. You will save a lot of money and space by installing a tankless water heater.

You are thinking storage water heaters are way less costly than these ones. You are right but think about 20 years of savings. Also, you need very low maintenance for gas tankless water heaters. So, we highly recommend that you go with tankless gas water heaters.


There are several certifications to ensure product safety for both of you and the environment. CSA certification is important in this regard.

CSA International (Canadian Standard Association) is a provider of product testing and certification recognized in the US and Canada. They test and give certificates to products of various categories including gas appliances and water heaters. They make sure that your product has safety measures, low-lead emission and sanitation standard.

IAMPO means International Association of Plumbing and Mechanical. They give certificates based on Uniform Plumbing Code (UPC) to ensure public health safety.

See which gas tankless water heater has what certifications and be assured of safety.


Our 10 Best Gas Tankless Water Heater has to price with a very low price to very high price. You will definitely find the perfect one for you in this wide range of price.

Our pick

We’re at the bottom of the Best Gas Tankless Water Heater review. Considering everything, our Champion gas tankless water heater is Takagi T-KJr2-IN-LP and Takagi T-KJr2-IN-NG. Both models have same specs. One is propane powered and another is natural gas operated. Takagi tankless water heater got everything you would wish for.

Our 1st Runner-up gas tankless water heater is the Eccotemp L5 portable water heater. It is the best-selling water heater on Amazon. Also, it has the lowest price on the list. It’s best for the people on a tight budget.

Our 2nd Runner-up gas tankless water heater is Rheem RTGH-95DVLN. It is the most energy-efficient unit on our list. With energy factor at 0.96, Rheem tankless water heater wastes only 4% of the energy given. Durability is assured as it is Rheem manufactured water heater.

Choosing between Propane and Natural Gas is totally a personal choice. Both have merits and demerits. If you consider about costing, then Natural Gas is the winner.

This is it, you can make up your mind based on the information above or see our individual product reviews for better judgement.

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