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9 Best Tankless Water Heaters For a Continuous Water Supply In 2019

Last Updated: 01 November 2019

It’s great when hot water always flows from the tap? This can be achieved with the help of the best tankless water heater. But the variety of offers on the market is amazing, and you want to buy the best model and do not know which one to prefer? We will show you how to choose the best heater without a storage tank. We will tell how to pick it up taking into account operating conditions. Let us designate what capabilities equipment should have to meet the individual users’ needs. We’ll discusses the main criteria for selecting the optimal model, give the rating of the top tankless water heaters.

What Is A Tankless Water Heater?

What Is A Tankless Water Heater?

The best tankless water heater is made for heating water. Externally, the device looks like a small plastic box. Cold water and electricity are connected to it. On the other side, there is an outlet for hot water. You can adjust the degree of heating in two ways: mechanical or electronic. When it comes to its operation, it's quite clear from the name. This is possible due to its design, which includes a heat exchanger, a tubular electric heater or a gas burner, control and automation devices. The latter include various sensors and devices. Some of them allow heating to be switched on in automatic mode when a flow occurs. Others protect the unit from running "dry" or under insufficient pressure and prevent the unit from overheating. Still, others provide safety, prevent electric shock and protecting current-carrying chains from overloads.

Why Do You Desperately Need This Product?

It saves not only the room space due to its compact size, but also the time, which is currently very important. For example, to obtain 10 liters of hot water, a cumulative modification heater will work for 25 minutes, 100 liters will need about 5 hours. And the tankless heater will give you an unlimited amount instantly and without interruption, you just have to turn the tap.

Tankless Water Heater FAQ

How It’s Installed?

It is installed according to the instructions that are available in each model. Nevertheless, in most cases, it is better to invite a specialist who will do everything correctly.

Where Is It Installed?

The device can be installed in the bathroom, on the floor, on the wall – it all depends on the model and its purpose.

When To Flush A Tankless Heater?

If you understand that the top-rated tankless water heater supplies less water, most likely, it must be cleaned. Read the manual on how to do this.

9 Best Tankless Water Heaters Compared And Reviewed

1 place :

Best Overall: Stiebel Eltron 224199

Best Overall: Stiebel Eltron 224199

One of the main advantages of this particular model is the absence of mechanical switches and high-quality electronic components with a reliable cover. This is the best electric tankless heater that doesn’t make you wait a long time if you raise your water consumption. You can simultaneously use a shower, a bathtub, a dishwasher and hot water will be everywhere. This device has an elegant design which will perfectly fit into a small apartment and house, and it will also consume electricity sparingly. The manufacturer gives a three-year warranty for the product, so it is better to get a professional to install your new water heater avoid any difficulties if you’ll ever need to use warranty.

Q: Can I use 200v60hz three-phase? 208v or less can not be used?

A: It requires 2 independent 208 volt single-phase circuits (each independent circuit has 3 wires connected as Load 1, Load 2 and Neutral).Three phase typically has 4 wires, with 1 being neutral / ground.

Q: I currently have 3 separate 40-amp breakers. Will this work with this model since it still adds up to 120, or does it HAVE to be 2 60-amps?

A: You need two 2-wire circuits, plus ground. So that means two 2-pole breakers, 60 amps each.

Q: Do you need a blower assembly unit #9004316 for a hot water heater?

A: It's electric not gas-powered, so no on the blower.

pros +

Noiseless operation Static temperature Elegant design

cons -

Disclaimer in the guarantee agreement Price

2 place :

For A Big House: Rheem RTGH-95DVLN 9.5 GPM

For A Big House: Rheem RTGH-95DVLN 9.5 GPM

It is one of the best house gas tankless water heaters on the market. It is ideal for a large house and apartment, as you can use a dishwasher, shower, and laundry simultaneously. At the same time, it spends very little energy. Yes, the price of this largest tankless water heater is high, but it completely pays itself out if you use a lot of hot water. Another advantage is a quiet and silent operation. In addition, this unit works perfectly even during low temperatures.

Q: What else is needed to install this unit?

A: Exhaust pipe and right size gas pipe fittings.

Q: Does this include hot/cold maintenance water valves?

A: Maintenance valves are not included.

Q: Can both horizontal runs of PVC vent be offset sideways, downward or upward to avoid obstacles?

A: Sideways, yes, but there should be a consistent slight slope away from the heater so condensation can drain.

pros +

Reliability and a 10-year warranty Smart control functions and remote control included Ideal for industrial conditions, as well as a large house or apartment Silent

cons -

Very high price

3 place :

Affordable Price: Takagi T-KJr2-IN-NG

Affordable Price: Takagi T-KJr2-IN-NG

Looking for the best tankless heater for an apartment or a small house, which will not let you down even during cold temperatures? Then this option is what you need. If you are limited in budget, but you need a device that will allow you to use several hot streams at the same time and not to overpay for the unit at the same time– give preference to Takagi tankless heater. All tankless water heater reviews prove that this device is very reliable.

Q: How well does the system handle hard water?

A: If your water hardness is greater than 7, the instructions say that you should install a scale inhibitor, which is just a replaceable cartridge (e.g., Aquapure). Otherwise, you risk fouling the heat exchanger over time, and that's difficult to remedy.

Q: What size gas line is required?

A: 3/4 inch gas line is required.

Q: What are the venting requirements for this indoor unit?

A: 4-inch double-walled pipe.

pros +

The cheapest among inexpensive gas heaters Easy to use, you can control it using the remote control that comes with the kit Easy and fast installation Compact, stylish and reliable

cons -

Although it is easy to install, you will need the help of a specialist to install everything correctly and not to break the warranty

4 place :

For Sink: Bosch Tronic 2.5-Gallon Electric Mini-Tank Heater

For Sink: Bosch Tronic 2.5-Gallon Electric Mini-Tank Heater

According to Bosch CV, this is the best electric heater for installation in the kitchen. It is easy to place it; by the way, you can install it on the floor, on the shelf or under the sink. It is simple, reliable and noiseless. Yes, its option is not suitable for using a dishwasher or a shower, but it is enough for the sink. Bosch electric tankless heater is compact, saves electricity and delivers enough water. Moreover, the well-known brand guarantees its quality.

pros +

Compactness Guarantee of a well-known brand Quiet and economical Low water consumption Easy to maintain

cons -

Suitable only for sinks

5 place :

Top Efficiency: Noritz NR981-SV-NG Indoor-Outdoor

Top Efficiency: Noritz NR981-SV-NG Indoor-Outdoor

An excellent powerful heater, which is highly efficient, as it heats up to 9.8 gallons per minute. Add here the design of the Low Nox and the temperature range of 100 ° F – 140 ° F and you will get an excellent device that can be used in a big house, apartment or even a cottage. If you are looking for an economical, highly efficient model with a quality, guarantee from the manufacturer and do not want to overpay – choose Noritz tankless heater.

Q: Starts heating with electricity?

A: Yes, it needs a dedicated 110 volt outlet for the controls to operate.

Q: Is this a whole house unit or a point of use?

A: Whole house unit.

Q: Will this work on a 5.5 bath house?

A: Maximum 1.5 baths, I installed mine close to the shower and faucets.

pros +

High efficiency Stylish design Large temperature range

cons -


6 place :

For Kitchen: EcoSmart 27

For Kitchen: EcoSmart 27

This is another model for installation under the sink in the kitchen. It is enough for comfortable use. The device is powerful and compact. Judging by various user reviews, this unit recommends itself from a very good side, which is confirmed by the brand guarantee. In general, a good and affordable energy efficient heater for use in the kitchen or small bathroom.

pros +

Compactness Normal consumption, which ensures low energy costs Reliable

cons -

Big size Loud at work

7 place :

For Studio Apartment: Rheem RTEX-13

For Studio Apartment: Rheem RTEX-13

An excellent option for those who want to install a multifunctional device. With Rheem heater, you can wash in the shower and wash dishes in the kitchen. Another advantage is its compactness. It perfectly fits into the interior, and does not take up much space; this indicates that it is ideal for even a small-shelled house. Outside the device, there is a thermostat with an LED display, which makes it easy to control and adjust the desired temperature.

pros +

Compactness Digital thermostat Low price The best option for a studio apartment

cons -

Not suitable for houses with several showers

8 place :

For Residential Use: Rinnai RUC98iN Ultra Series Natural Gas

For Residential Use: Rinnai RUC98iN Ultra Series Natural Gas

Perhaps, we would have put a Rinnai tankless heater on the first step in our rating, if not for the high price. If you do not take into account the price, then this is the best that you can think of for a large apartment building, as it works perfectly at any temperatures, even the coldest. You will be able to control the device settings yourself, choose any desired mode. Also, the manufacturer included an innovative circulation line in this heater, which is an undoubted plus. If we talk about cost, then it will be more than paid off when using the device, since it is economical and very efficient.

pros +

Easy to install and use Does not need expansion extension Quiet Greater efficiency due to condensation water Guarantee from the manufacturer Ideal for any apartment building

cons -

The most expensive option The ventilation kit does not come with the device

9 place :

For Summer Vacation: Eccotemp L10 Portable

For Summer Vacation: Eccotemp L10 Portable

This portable heater is ideal for use in a summer residence, a country house, campsite or cabins. Just connect this gas tankless heater to the garden hose and gas main and use a warm shower at the end of the day. Moreover, this propane-powered best tankless gas heater can heat water below zero. This device has an electronic ignition, which makes it great for off grid or other areas if electricity is not available. The model can operate with 12 volt.

pros +

Powerful Able to heat temperatures even below zero Best outdoor device Works through a garden hose Quality guarantee from the manufacturer

cons -

You must wait for the water heating Large propane consumption

Types Of Tankless Water Heaters

There are two main types of tankless heater available on the market now. They are divided into gas and electric ones by energy source and into pressure and non-pressure by type.

Tankless Water Heater


Of course, the best natural gas heater is much cheaper than an electric one. Modern models have the same comfort degree as their electrical counterparts. Another advantage is high power, and therefore, performance. It can be connected to all points with hot water extraction and, at the same time, ensure their simultaneous operation.


In some cases, it is not possible to use gas equipment for technical reasons. In addition, there are also factors of expediency. For example, if the apartment is connected to a centralized hot water supply system, it is much easier to install an electric heater. Advantages of such a type are compactness and unpretentiousness in work. Also, no permits or approvals are required for installation. The only thing you need is metalwork or electrical installation skills. If this does not work out, you can always turn to an electrician for help. In addition, electric tankless hot water heater reviews will help you to connect such devices with ease.

Best Tankless Water Heater Buying Guide – What To Look At?

In order to choose the right heater for your dwelling, you must consistently answer a number of questions:

Source Of Energy: Gas Or Electricity?

If there are gas channels in your house and the housing office allows gas equipment installation, the gas heaters will be the most preferable option.

The power of a standard gas tankless heater is enough to heat water for a shower in the winter. If your house is not equipped with natural gas, you will have to install an electric model.

Types Of Heaters: Pressure Or Non-Pressure?

Review of Tankless Water Heater

For the hot water supply of the whole apartment, you will have to install a pressurized device, which is connected directly into the cold water standpipe. Such equipment can provide several points with hot water. If you just want to take a shower anytime in the summer – choose a non-pressure heater. As a rule, such devices have a small capacity and are equipped with shower nozzles. However, you must bear in mind that they are suitable for heating water in the summer. In winter, when the temperature in the pipes drops to the 5 degree mark, you will have problems with a low-powered non-pressure device.

They are connected to the water system at home. That is, the water in it is under pressure constantly. But while in the house all the taps are shut off and water is not consumed, it does not work. As soon as one of the taps comes off and there is a stream of water coming through the heater, it turns on. Such a device is able to work at several points. However, to ensure the heating of large water amounts, it must have a large capacity – up to 36 kW.


They can be connected to almost any water source, but the main thing is that this source has a tap to shut off the water supply. In order for such a heater to start working, it is enough to turn it on in the main, set the water temperature and open its supply on the tap. The heater will continue to operate on the water flow, that is, if you cut off its flow, it will automatically turn off. Because of this feature, this type is not able to provide multiple intake points with hot water. But since they work only on one point, their power is relatively small – from 3 to 8 kW.

What Capacity Do I Need?

It will be much easier for you to determine not the capacity, but water consumption. This parameter is indicated in the device’s passport. Open the tap in the usual mode and notice how long it takes to get a full water 10-litre bucket, for example. The resulting data is converted into consumption per minute and feel free to go to the store. Now you can accurately find the most suitable tankless heater.

The Best Tankless Water Heater - Final Advice

The best tankless water heater is the right investment for your money. Thus, you not only get hot water when you want, but you also control the its heat level and the f electricity or gas amount that is spent on heating it. The best tankless water heater is much more convenient than being dependent on a common water supply system.

The leader in our rating Stiebel Eltron. This heater is incredibly powerful, quiet in operation and compact enough. It is very easy to manage, and there is a guarantee from the manufacturer. Yes, it is somewhat more expensive than other options, such as Rinnai RUC98iN Ultra Series or Noritz NR981-SV-NG, but this device is definitely worth the money spent on it.

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