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7 Best Tankless Gas Water Heaters (Reviews of 2021)

Like the idea of a never-ending supply of hot water and lower energy bills? Then a tankless water heater could be for you.

Read on as we take you through the features of seven of the best tankless gas water heaters out there.  And our buying guide will make the task of choosing one as easy as pie.

So let’s get started!

Rinnai V Series HE Tankless Gas Water Heater
Rinnai V Series HE Tankless Gas Water Heater

  • Wifi enabled, allowing you to schedule hot water via an app
  • Vacation mode to save money whilst you’re away
  • Nice and quiet

Gasland BE158S Tankless Gas Water Heater
Gasland BE158S Tankless Gas Water Heater

  • Lightweight, compact and fully portable
  • Easy to set up
  • Energy efficient


The Best Tankless Gas Water Heater of 2021

1. Gasland BE158S Tankless Gas Water Heater Budget Pick

Gasland BE158S Tankless Gas Water Heater

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Gasland’s BE158S is a great option for anyone looking for a portable water heater.

At a little under 15 pounds, it’s lightweight and compact enough to be taken on camping trips. And if you’re worrying about spending ages on complex set-up, don’t – it really is simple.

First, the supplied GHT garden hose is attached to the input fitting, and the shower head to the output. Then the gas supply line and regulator are attached to the heater. A hose with a second regulator then connects to your gas cylinder.

Insert two D cell batteries, turn on the water, and you’re good to go.

You won’t need to preheat the water, and it will keep running for as long as you need it. (Or at least until your gas cylinder runs out!)

The output is a maximum of 41,000 BTUs. That’s an impressive level of power for a portable unit. The water be heated at a rate of 1.58 gallons per minute. And the temperature and water flow are fully adjustable whilst you’re showering.

It’s energy efficient too. The propane heater exchanger and main burner decrease both energy consumption and noise. Gasland says this cuts power use by 11.5%.

As with the Girard, this needs the right conditions to work at its best. A water pressure of at least 2.5 PSI is an absolute must. That’s pretty low, so it shouldn’t be an issue in most locations. If the pressure doesn’t reach that level, though, the heater won’t fire.

There are multiple safety protection features so this can be used by all the family without issues. The unit includes a flame failure device, and automatically stops the water flow if it reaches over 167 degrees Fahrenheit.

And if there’s an unexpected flameout, it immediately switches off the gas supply.

It’s a good option to use in cold temperatures. The anti-freezing drain plug allows you to remove any residual water after use to prevent damage.

It’s not the best choice though if you plan on camping at altitude. Anything over 3,300 feet will cause it problems. The same goes for strong winds, which can extinguish the flame.


  • Lightweight, compact and fully portable
  • Easy to set up
  • Energy efficient


  • Won’t work at altitudes over 3,300 feet
  • Avoid using it in windy conditions.

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2. Rinnai V Series HE Tankless Gas Water Heater Our Top Pick

Rinnai V Series HE Tankless Gas Water Heater

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If you’re looking for a water heater to cope with the demands of your main home, consider Rinnai’s V series.

This tankless heater uses natural gas and is only suitable for installation indoors. It’s powerful enough to give you a maximum water flow of 6.5 gallons per minute. But the results do depend on the temperature of the groundwater in your location. And that in turn depends on the climate.

If you’re in an area where it’s cooler, the flow rate can be significantly lower. A groundwater temperature of 35 degrees Centigrade will produce a flow rate of 2.9 gallons per minute. That’s enough to heat two showers simultaneously, but that’s all.

In warmer areas, a groundwater temperature of 77 degrees Centrigrade will increase that flow rate to 5.7 gallons per minute. That’s enough for no fewer than five simultaneous showers.

And if you don’t have that many bathrooms, remember that other appliances use hot water too. A sink, washing machine or dishwasher will use roughly the same amount of hot water as a shower.

If water heaters can be considered clever, this one is a genius. It’s wifi enabled and is controlled by a mobile app which allows you to schedule hot water throughout the day.

And if you want to save energy while you’re on holiday, you can put it into vacation mode. Forgot to do that before you set off? Don’t worry, just fire up the mobile app and activate it remotely.

There’s also a leak detection feature. Any sign of a leak and the unit will switch off the water to limit damage. There’s enhanced scale detection to lower the risk of damage from limescale. And a temperature lock makes sure the water stays at a safe temperature at all times.

The unit is covered by a two-year warranty for the heat exchanger, 1 year for labor and 5 years for parts.

So far, so good. But it’s worth bearing in mind that installation does present some challenges. This is definitely a unit where it pays to get a professional to do the hard work. The manual isn’t as clear as it could be either.

And you will need to run the water for a couple of minutes before it’s nice and hot. You may find you use more water as a result. On the plus side, this runs surprisingly quietly, so you won’t disturb the household when you turn on the heat.


  • Wifi enabled, allowing you to schedule hot water via an app
  • Vacation mode to save money whilst you’re away
  • Nice and quiet


  • Installation is tricky – get a professional in
  • You’ll need to wait a couple of minutes for the water to reach optimal temperature.

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3. Excel LPG Tankless Gas Water Heater

Excel LPG Tankless Gas Water Heater

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If you want a heater for a location with low water pressure, Excel’s offering could be just what you need.

The magnetic water flow sensor means it will start with a water pressure of just 2 PSI.

That’s in contrast to conventional tankless heaters that use a rubber diaphragm. The diaphragm moves under the pressure of the water, pushing a pin that activates a switch. Typically, heaters using that design will need pressures of around 30 PSI to get going.

At the other end of the spectrum, it will cope with water pressures of up to 120 PSI without issue.

If you live in a small apartment, it’s powerful enough to be a solution for your whole home. It works equally well in mobile homes, recreational vehicles, rural cabins or even on boats. (These are all locations which often experience low water pressure.)

It’s suitable for residences with up to two and a half bathrooms and is fitted for multiple points of use. Just don’t try to use more than one appliance at the same time, or you’ll run into trouble.

Hot water is delivered as soon as you turn the tap. And it doesn’t require any venting, meaning there are no flues or ductwork to install. If you’re not replacing an existing tankless water heater, that’s a big advantage. We’d recommend a carbon monoxide detector, though, for reassurance.

While this heater can cope with extremes of water pressure, it’s more particular about incoming water temperatures. It’s recommended for incoming water above 50 degrees Fahrenheit. If you need it to handle temperatures down to 40 degrees, you’ll need to reduce the water flow.

And if the water is colder than that, it just won’t work.

The heat exchanger is pure copper. That means it’s highly thermally efficient, as well as durable. It comes with a lifetime warranty.

You’ll also need two size D batteries, which are included in the package.


  • Ventless design means no need for flues or ductwork
  • Copes effectively with very low water pressure
  • High quality heat exchanger comes with a lifetime warranty


  • Won’t cope with delivering hot water to more than one appliance at a time…
  • …or with water inflow temperatures below 40 degrees Fahrenheit.

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4. Rheem RTG-84XLN-1 Tankless Gas Water Heater

Rheem RTG-84XLN-1 Tankless Gas Water Heater

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Rheem’s tankless water heater offers mid-range efficiency with a best-in-class low flow activation. This requires a minimum flow rate of just 0.26 gallons per minute. So if you live alone or don’t use much water, this is a good option.

But don’t dismiss it if you have higher demand. It’s possible to link together multiple units to cope. And if you’re looking for a tankless water heater to cope with high altitudes, the hassle might be worth it. This will handle altitudes of up to 8,400 feet above sea level with ease.

The burner meets ultra-low emissions standards for nitrogen oxide, making it both safe and environmentally friendly. And there’s what Rheem call a “Guardian Overheat Film Wrap” to prevent temperatures rising to unsafe levels.

This is designed for outdoor installation, so you won’t need to worry about venting. It can handle some seriously chilly conditions too. It comes with freeze protection to guard against temperatures all the way down to minus 30 degrees Fahrenheit.

The standard heater will give you a maximum hot water temperature of 140 degrees Fahrenheit. If you want higher temperatures, upgrade kits are available.

If you’ve ever shrieked at a burst of cold water in your shower, you’ll like the hot start programming function. This keeps the heater in ready-fire state, so it’s ready to deliver hot water for back-to-back use. It comes with a digital remote control too.

The main downside here is that it can take some time for the water to get hot enough. There is, though, a clever “Water Savings” setting that reduces the flow at the tap while it’s heating up. That could save you up to 1,100 gallons per year, making it kinder to the environment – and your wallet.


  • Best-in-class low flow activation
  • Hot start programming delivers hot water for back-to-back use
  • Works even at high altitude


  • You’ll need to connect together multiple units if you have high demand
  • Takes some time for the water to get hot.

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5. Noritz NRC66DVNG Indoor Tankless Gas Water Heater

Noritz NRC66DVNG Indoor Tankless Gas Water Heater

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Noritz have been manufacturing water heaters for over 60 years. They introduced the world’s first electronically controlled water heater in 1981. With that pedigree, the NRC66DVNG is well worth checking out.

For households that need a heater to deliver higher flow rates, this is a great option. It offers an industry-leading rate of up to 6.6 gallons per minute, and will cope easily with multiple use points. If your household often has a couple of showers and the dishwasher running simultaneously, this will take the strain.

It’s designed to be installed indoors, so you won’t have to worry about harsh weather conditions affecting its performance. You will, though, need to make sure it’s properly vented.

Happily, a wide range of adapters and termination options are available to cope with all venting needs.

And because this is a high-efficiency condensing water heater, the exhaust temperatures are low. That means it doesn’t require stainless steel venting. The PVC alternative used here is much less expensive.

The default water temperature is 120 degrees Fahrenheit. This is displayed on the red LED display and regulated digitally.

The fuel use here is very efficient, which is good news for both your energy bills and planet Earth. And it runs very quietly – just a gentle hum as the water heats up.

It comes with a six foot power cord. And there’s a remote control panel which you can buy separately if you wish. That allows you to adjust the hot water temperature without fiddling with the switches on the heater.


  • High flow rate can provide simultaneous hot water to multiple use points
  • Very energy-efficient – great for household bills and the environment
  • Low temperature exhaust allows the use of inexpensive PVC venting


  • You’ll need to buy the remote control panel separately.
  • Expensive – but you can save money by using PVC venting.

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6. VEVOR Natural 18L Tankless Gas Water Heater

VEVOR Natural 18L Tankless Gas Water Heater

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If need a gas water heater that can be used in locations without electricity, VEVOR’s heater may be the answer.

This uses natural gas and requires proper venting. It’s wall mounted, and its slimline design won’t take up a lot of room.

It will heat up to 4.75 gallons of water per minute and requires a water pressure of just 2.9 PSI. And it will work effectively up to a maximum water pressure of 116 PSI.

When it comes to installation, the manual unfortunately isn’t as helpful as it could be. Check you have all the right parts before you start. This model comes with half-inch fittings for the water pipe.  And the vent opening on the heater is an unconventional size, which makes for a bit of extra work.

Get the gas and water regulators properly synched, though, and you’ll have hot water in seconds. For homes with low to medium levels of demand – say, two bathrooms – this will work very well.

The LED display is lit by two D batteries. Note that it doesn’t come on as soon as the batteries are installed. The display lights up when the water is running, and when there’s sufficient gas and water pressure.

Install this correctly, and this is an effective water heater. And it carries a very competitive price tag – it’s a quarter of the cost of other heaters on this list.


  • Delivers hot water in seconds
  • Doesn’t require electricity
  • Extremely competitive price tag


  • The unconventional vent openings and unhelpful manual make installation trickier than it needs to be
  • Not the best choice if you have a high-demand household.

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7. Girard 2GWHAM On-Demand Tankless Gas Water Heater

Girard 2GWHAM On-Demand Tankless Gas Water Heater
Image: Girard

If you’re looking for a robust water heater that’s great for recreational vehicles, Girard’s 2GWHAM is well worth a look.

It’s sturdily constructed and uses a brushless motor to run quietly. That motor means it’s efficient in its use of fuel too. It runs on 12 Volts of power, operating at less than three Amps.

There’s no need for any specialist plumbing or gas lines here, making installation relatively straight forward. But unless you’re a plumber yourself, this is still a job where it’s sensible to bring in professional help.

The output here is 42,000 BTUs, which makes it well suited to an RV.

For anyone not familiar with the lingo, BTU stands for “British thermal unit”. The higher the number of BTUs, the stronger the heating power of the unit. 42,000 BTUs means this heater can raise the temperature of 42,000 pounds of water by one degree in an hour.

In practical terms, that means that you can have a long, hot shower. And you won’t have to worry about it suddenly getting cold when you reach the bottom of your water tank!

The unit also contains its own microprocessor. This monitors the temperature and flow rate of the cold water coming in and the hot water going out. The result is a stable flow of water at your desired temperature.

There are a few things to bear in mind here in order to get the best results.

The main one is that you’ll need a flow rate of at least 0.9 gallons per minute. If it’s lower than this, the heater won’t fire.

This is something that’s fairly easy to check. Run the water through your shower head into a bucket for one minute. Make sure you use a stopwatch to time it accurately. Then measure the amount of water in the bucket. If it’s at least a gallon, this heater will work fine.

The other thing for RV-users to note is that adding cold water to adjust the temperature doesn’t work well. It can interfere with the water flow and upset the microprocessor. So set it at a temperature that works without you having to add cold water.


  • Great for RVs, with no need for specialist plumbing
  • Brushless motor is quiet and efficient
  • 42,000 BTU input allows long, hot showers


  • Won’t work with a flow rate of less than 0.9 gallons per minute
  • Adding cold water to adjust the temperature doesn’t work well.


Buying guide

Still not sure which is the right tankless gas water heater for you? Answer the questions in our buying guide and you’ll have everything you need to make the right choice.

Where will your water heater be located?

tankless water heater gas

Do you need a portable solution you can take camping? Or are you looking for something to be permanently installed in your home?

If you need a water heater for a recreational vehicle or boat, look for one that can handle low pressure. The Excel heater on our list will cope with the lowest water pressures, right down to 2 PSI.

Some heaters use batteries instead of electricity, perfect if you don’t have a power supply.

And don’t forget that outdoor temperatures will affect your water heater too. If you live in an area with a very cold climate, look for models with anti-freezing functions. And groundwater temperatures can hugely affect flow rates, so check the specifications before you buy.

High or low demand?

tankless gas water heater

Are you looking for a portable heater to power a single shower while camping? Or do you need something that will provide simultaneous hot water for a number of appliances?

Don’t assume that any heater will work in low-demand situations. In some cases, they’ll struggle to fire up. Rheem’s RTG-84XLN-1 is one heater that will cope well.

And for higher demand, you’ll need more powerful options. The Noritz heater on our list is great for situations where you need hot water for multiple uses at once.

Check efficiency

gas tankless water heater

A fuel-efficient water heater can save you a lot of money, as well as being kind to the environment. In some areas, you may even benefit from a rebate if you buy a high-efficiency water heater. So check out efficiency ratings before you buy.

And remember that water efficiency is important too. The water saving setting on Rheem’s heater could save more than a thousand gallons of water a year.

Ready to get hot water on demand?

That brings us to the end of our reviews of the top tankless gas water heaters on the market today. Wherever you need hot water – home, RV or sailboat – we hope you’ve found something that ticks all your boxes.

Whatever option you choose, a tankless water heater means instant hot water and lower bills. We think that’s an investment that’s well worth making.

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