Tankless Water Heater Reviews – Best Models Review

I decided to create this page of tankless water heater reviews after reaping the many benefits for the last few years. I decided to make the switch from traditional tank heaters to tankless some years back after receiving testimony after testimony from my customers about how much they loved their new heaters compared to what they had before. I have been a disciple ever since. The best tankless water heaters offer several benefits over traditional heaters. I’ve seen a lot of individuals and businesses switching to tankless systems mainly because of the savings they stand to make in the long run. Tankless heaters have won high praise for their low monthly running cost, energy efficiency, and a longer lifespan. And you can also take a 5-hour shower without ever running out of hot water.

Whatever your reason for wanting to switch, it is important that you buy the best tankless water heater for your needs in order to receive the benefits it brings. I have included a buying guide below the reviews to help you determine the right tankless water heater for you. It is important that you read this guide to help you determine the right size heater to buy. Then go through the review list below to select a heater that best fits your needs. The order of the reviews is not important. Every heater on the list is of the highest quality and capable of doing the job is designed to do.

#1 Stiebel Eltron Tempra 24 Plus Electric Tankless Whole House Water Heater

Rating: 5 Stars out of 5 | Type: Electric | Temperature rise: 65°F rise @ 2.52 GPM to 35°F rise @ 5.4 GPM | Click For Today's Best Price

 

Stiebel-Eltron-Tempra-24-250 tankless water heater reviewNote: Read my full review of this tankless water heater for information on home electric requirements before deciding to buy this unit. Some older houses may not have the required electrical wiring to handle this heater.

I have picked the Stiebel Eltron Tempra 24 Plus is the best tankless water heater for its endless hot water supply, its high built quality, its proven reliability and excellent user feedbacks. The Tempra 24 is a whole house tankless water heater providing endless hot water for homes with two or more showers plus sinks and other appliances that use hot water. Those living in very cold climates may have to install two units to satisfy hot water needs for a large home.

The 65°F temperature rise at a flow rate of 2.52 GPM is enough to provide a hot comfortable shower over and over with great reliability. Provides excellent hot water supply for dishwashers, washing machines, faucets and other hot water applications around the home. The flow rate can go as high as 5.4 GPM to supply hot water to Roman or Jacuzzi tubs. It heats water to a maximum temperature of 140°F. The variable flow rate control ensures that the temperature of the water remains constant by making small adjustments to the flow rate when needed. The self-modulating control ensures that the heater uses only the minimum amount of energy it needs, saving you money on your bills.

One safety feature I love is the ability to set the maximum temperature to prevent accidental scalding.

I had to pick this as my top pick because it has the highest consumer ratings on the market with thousands of very happy and satisfied customers. When it can, “boil a Canadian like a lobster,” what more is there to say?

In mine and many happy customer’s opinions, you simply cannot buy a better tankless water heater than the Stiebel Eltron Tempra 24 Plus…        Click here to read the full review

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#2 Rinnai RL75iN Natural Gas Tankless Water Heater Review

Rating: 4.7 stars out of 5 | Type: Natural Gas | Temperature Rise: 70°F @ 4.3 GPM, 50°F @ 6.0 GPM. Has a hot water flow rate of 0.26GPM to 7.5 GPM. The higher the flow rate, the lower the temperature rise | Price: Click For Today's Best Price

 

Rinnai-RL75iN-tanless-heater-reviewRinnai RL75i is a whole house tankless water heater. If you have a house where three people take a shower at the same time, this heater can produce enough temperature rise to comfortably supply hot water to all three showers at the same time. I don’t personally have this model but a friend of mine has it in their home. They live in a very close climate and during winter, this unit supplies enough hot water for two showers and the washing machine at the same time. This is more than most homes will use at any single time.  Capable of producing hot water of 120F at a flow rate of 7.5 GPM (gallons per minute), this heater could manage any hot water demand around your home.

The RL75i is a high-efficiency energy star approved heater with an energy factor of 0.82. This qualifies it for government tax breaks and other utility rebates. Please note that the RL75iN uses only natural gas and not propane. If your gas supply is propane, then you need the RL75iP. Both have exactly the same BTU rating and function the same way except the type of gas they use. There is also an indoor and outdoor model. The RL75iN is an indoor unit. The outdoor model is the RL75e.

The Rinnai RL75 models can also be used in industrial applications. It is designed with high-quality parts which are backed up with a 12-year heat exchanger warranty and a 5-year other parts warranty.

This heater works great and will serve you with an endless supply of hot water and save money on your utility bills in the long run. The only downside to owning this is that you’ll have to wait a few seconds for the hot water to arrive. The farther the unit is located from the faucet, shower or appliance, the longer it will take the hot water to arrive. If you want to take a shower, expect to waste about 2 gallons of cold water before the hot water arrives. If you don’t mind this wastage, then this is an excellent tankless hot water unit to buy for your home…      Click to read my full review including more details on installation, usage and its most important features.

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#3 Rheem RTG-64XLN Outdoor Tankless Natural Gas Water heater Review

Rating: 4.5 stars out of 5 | Type: Natural Gas | Temperature Rise: 77°F Rise @ 3.3 GPM up to 35°F Rise @ 6.4GPM. Provides enough hot water for any household application | Price: Click For Today's Best Price

 

Rheem-RTG-64aXLN-tankless-heater-reviewThe RTG-64XLN is a natural gas powered outdoor whole house tankless water heater for your home. It can support up to a 35°F temperature rise at a flow rate of 6.4 GPM. This will be able to supply enough hot water for three simultaneous showers. If you need a really hot, steamy shower, then the unit can produce a temperature rise of 77°F at a flow rate of 3.3 GPM.

Basically, this unit should be enough to satisfy the hot water needs of a large family with 2 -3 bathrooms. It will also supply hot water to your faucets and appliances such as laundry machines and dish washers. My research has shown an overwhelmingly positive feedback on this unit.

If you live in a very cold climate and have a very high demand for hot water, you might need to get two units to satisfy your needs. Those living in wintery conditions will also love the freeze protection feature which allows the unit to function in sub-zero temperatures.

This tankless water heater model must be installed outdoors. Installation is easy but if you are not good at following instructions or you simply do not know what you are doing, it will be best to call for help installing the unit. If you need an indoor unit, the indoor version of the Rheem RTG-64XLN is the Rheem RTG-64DVLN. The RTG-64LN runs on natural gas. If you want a unit that runs on propane gas, then you should get the Rheem RTG-64XLP for outdoors or the RTG-64DVLP for indoors.

One user wrote: ” Nice low price, works very well and supplies plenty of hot water to my three bathroom house with 6 occupants. A strong unit I strongly recommend.”

Click here to read my full review of all the features, installation and usage tips.

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#4 EcoSmart ECO 27 Electric Tankless Water Heater Review

Rating: 4.3 Stars out of 5 | Type: Electric | Temperature Rise: 65°F Rise @ 2.84 GPM, 55°F Rise @ 3.35GPM, 45°F Rise @ 4.10 GPM, 35°F Rise @ 5.27 GPM | Price: Click For Today's Best Price

 

EcoSmart-ECO-27-tankless-heater-thumbThe Ecosmart Eco 27 is a gem of a tankless water heater and would look so good on your wall. This unit is a whole house residential or commercial application electric water heater. It is capable of supplying endless hot water to a home with 2 bathrooms. The peak flow rate is 5.3 GPM with a 35°F temperature rise. It can produce a high-temperature rise of 65°F at a flow rate of 2.84 GPM. This is enough for a hot steamy shower for two people at the same time. The thing is most of us will only have a maximum of two people taking showers simultaneously at home.

If you have a very high hot water demand, such as having the washing machine and dishwasher drawing hot water at the same time while 3 people are taking hot showers simultaneously, you may need to install two units in your home or get the higher rated ECO 36. But as long as you don’t plan on running every hot water application at the same time, this unit is more than capable of meeting your hot water needs.

One thing I love about this heater is the fact that is self-modulating. This means it will automatically adjust the amount of energy it uses based on your demand for hot water. It always strives to use the minimum amount of energy possible, saving money on your energy bills.

The Ecosmart Eco 27 is very well made with first-rate materials. The inner components are well laid out and easy to access. If you ever need to replace a component, they are readily available. They believe so much in the quality of their product that they offer a lifetime warranty on parts. Now how do you beat that?

In my opinion and from having talked to other people in the field, the Ecosmart Eco 27 is one of the best electric tankless water heaters you can get out there. It works well and it is long lasting. As one user wrote, “you simply can’t beat it”…     Click to read my full review including a look at all the features, installation and use.

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#5 Takagi T-KJr2-IN-NG Indoor Natural Gas Tankless Water Heater Review

Rating: 4.6 stars out of 5 | Type: Natural Gas | Temperature Rise: 70°F Rise @ 3.3 GPM to 35° Rise @ 6.6 GPM | Price: Click For Today's Best Price

 

Takagi-T-KJr2-IN-NG-tankless-water-heater-reviewThe Takagi T-KJr2-IN-NG is an indoor whole house natural gas tankless water heater. Producing a 70°F temperature rise at 3.3 GPM, this unit can produce enough hot water for two simultaneous showers. It is ideal for a house with 4 bedrooms and 3 bathrooms. It will comfortably serve the hot water needs of a family of 5 with no problems. I installed several of these units for clients and I haven’t had a single complaint about the unit from any of them.

The Takagi T-KJr2-IN-NG is to be installed indoors only and runs on natural gas only. If you need an outdoors model of this unit, then you should get the Takagi T-KJr2-OS-NG. If you want a unit that runs on propane gas, then you should get the Takagi T-KJr2-IN-LP for indoors or the Takagi T-T-KJr2-OS-LP for outdoors. All of these models have the same flow rates and temperature rises.

The unit can produce hot water at a peak flow rate of 6.6 GPM at a temperature rise of 35°F. This flow rate is enough for some commercial applications. I have seen comments from users in very cold climates who claim the unit works perfectly during the winter. I can confirm this to be true.

Takagi is a Japanese manufacturer and the quality of their units is unparalleled to none.  This unit will provide endless hot water, time after time, to your showers, sinks and other appliances that use hot water such as dishwashers and washing machines.

If you run a hotel or motel, this unit can supply hot water to several rooms. You’ll start to notice a significant drop in your monthly gas bills after installation. It is more expensive to install than a traditional tank heater but the savings you make on your monthly gas bills far outweigh the initial installation cost.

I highly recommend this tankless heater.

Click here to read the full review including information on installing the unit, gas line requirements, unit features and using the unit.

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#6 Eccotemp FVI-12-LP Propane Gas Tankless Water Heater Review

Rating: 4.0 Stars Out of 5 | Type: Liquid Propane Gas (LPG) | Temperature Rise: 77°F Rise @ 2.3 GPM, 65°F Rise@ 3.0 GPM, 55°F Rise @ 4.0 GPM, 45°F Rise @ 4.3 GPM | Price: Click For Today's Best Price

 

Eccotemp-FVI-12-LP-tankless-water-heater-reviewI included this on my list of the best tankless water heaters as an option for those a bit more limited budget. The unit is a whole house water heater with some limitations. For instance, this unit is not the most ideal for simultaneous showers if you want a hot steamy shower during the winter months. If you family takes turns to shower, then this unit is more than capable of producing enough hot water for a steamy hot shower. If you don’t like your showers too hot, then you will be able to squeeze two simultaneous showers out of it.  This tankless water heater is ideal for a family of 1 to 3 people. My research has shown that you can take as much as 90% off your monthly energy bills if you replace your current traditional tank heater with this unit.

The Eccotemp FVI-12-LP has a peak flow rate of 4.8 GPM with a 45°F temperature rise. The unit can produce an optimum temperature rise of 77°F at a flow rate of 2.3 GPM. The maximum temperature is 150°F. It can provide enough hot water for your showers (provided you shower sequentially), sinks and home appliances that use hot water. It runs on propane gas and not natural gas so make sure you have the right gas supply. Read the full review for gas line requirements.

One thing I like about this water heater is that it comes with everything you need to install the unit out of the box. It is easy to install but you should call an installer if you don’t know how to follow instruction or you are not comfortable doing it yourself. It can be mounted on the wall and takes up very little space.

There is a 2-year parts warranty, which isn’t very long compared to some other brands, but if you follow the maintenance instructions, this unit will supply endless hot water for your small family at only 30% of the cost of running a regular tank water heater for years to come. The Eccotemp FVI-12-LP has an excellent value for money.

Read the full review including information on gas line requirements, installation requirements, features and how to use the unit and tips for optimum use.

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#7 Stiebel Eltron DHC-E12 E Series Electric Tankless Water Heater Review

Rating: 4.4 Stars Out of 5 | Type: Electric | Temperature Rise: 65°F Rise @ 1.26 GPM, 55°F Rise@ 1.49 GPM, 45°F Rise @ 1.95 GPM, 35°F Rise @ 2.52 GPM | Price: Click For Today's Best Price

 

Stiebel-Eltron-DHC-E12-E-tankless-water-heater-reviewThe Stiebel Eltron DHC-E12 E is the second low-cost unit included in this review of the best tankless water heaters. This unit is more of a point-of-use heater rather than a whole house unit. However, you can use it as a whole house unit for a small household with low to medium flow rate requirements. Basically, this unit is good for supplying endless hot water for a single shower with low to medium flow rate or two sinks with the same level of hot water demand. Will it work with a washing machine or a dishwashing unit? The answer is yes, depending on the hot water demands of your appliances and how close the unit is installed to the appliances.

If you take hot showers one at a time in your home, and run other hot water applications one at a time and live in a warm climate such as Florida, then this unit is more than adequate for your hot water needs. You will save money on water and electric bills down the line. This unit is cheap compared to other tankless water heaters and the initial installation cost is not high. It is a cost effective choice for anyone looking to switch to a tankless water heater without paying the higher initial cost.

The unit has a peak flow rate of 4.5 GPM at a 20°F temperature rise. It has an optimum temperature rise of 65°F at a flow rate of 1.26GPM. You can achieve a temperature rise of 45°F at a flow rate of 2.3 GPM. For businesses, this will make a perfect water source for handwashing sinks.

The unit itself looks very sleek and looks beautiful on the wall. It is well built and comes with a 3-year parts warranty.

Overall, this unit is an excellent source of hot water for a small family or for point-of-use applications. It will keep the hot water flowing at your required temperature for as long as you need it. And it saves money on your monthly water and electric bills. This is one of the best tankless water heaters for low to medium demand applications.

Click here to read the full review for information on installation, features and how to use the unit.

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#8 Takagi T-T-KJr2-OS-LP Outdoor Propane Tankless Water Heater Review

Rating: 4.5 Stars Out of 5 | Type: Liquid Propane Gas (LPG) | Temperature Rise: 70°F Rise @ 3.64 GPM, 60°F Rise @ 4.0 GPM, 50°F Rise @ 4.6 GPM, 40°F Rise @ 5.7 GPM, 35°F Rise @ 6.4 GPM | Price: Click For Today's Best Price

 

Takagi-T-T-KJr2-OS-LP-tankless-water-heater-ReviewThe Takagi T-T-KJr2-OS-LP is the propane gas powered, outdoor version of the Takagi T-KJr2-IN-NG I reviewed above. Yes, the T-KJr2 is so good I had to include it twice. Unsurprisingly, this tankless water heater has similar performance and ratings as its natural gas counterpart.

This unit has enough temperature rise and flow rate to serve to supply the entire hot water needs for a 4 bedroom home with 3 bathrooms and about 6 occupants. Two people can take steamy hot simultaneous showers with a washing machine or dishwasher drawing hot water at the same time. With nothing else drawing hot water, the unit can comfortably supply enough hot water for 3 showers simultaneously. In colder climates, where the temperature of water entering the unit may be very low, the unit might only supply hot water for 1 shower at a time. However, is still possible to achieve two simultaneous hot showers in cold climates if you like your hot showers at 110°F.

The unit in this review has a peak flow rate of 6.4 GPM at a temperature rise of 35°F. It can achieve a 70°F temperature rise at a flow rate of 3.4 GPM.

You can install the unit yourself if you know what you are doing. It is not difficult to install. The unit is easy to use and will supply endless hot water as long as you need it at the temperature of your choice.  The unit comes with a remote control to control the temperature from inside your home.

I know users who have used this tankless water heater for several years without any problems. If you follow the maintenance recommendations in the manual, this unit will supply hot water and save you money on your monthly energy and water bills for years to come.

Click here to read the full review including information on installation, usage, and features.

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#9 EcoSmart ECO 11 Electric Tankless Water Heater Review

Rating: 4.2 Stars Out of 5 | Type: Electric | Temperature Rise: 65°F Rise @ 1.37 GPM, 55°F Rise @ 1.61 GPM, 45°F Rise @ 1.97 GPM, 35°F Rise @ 2.54 GPM | Price: Click For Today's Best Price

 

EcoSmart-ECO-11-Electric-tankless-water-heater-reviewPicture this, you are a single person living in a small home with a single bathroom and two sinks (one in the bathroom and one in the kitchen). You need a high-quality water heater for hot showers and to provide hot water to your sinks. Your budget is a bit limited but you desire the best quality heater. If you fit this description, then you can’t go wrong with the Ecosmart 11 electric tankless water heater.

The unit is also ideal for a small family with 1-2 bathrooms provided you take turns to take a shower. The unit can produce enough temperature rise to supply hot water to only one shower at a time. If this unit can meet your demands, then the Ecosmart 11 is the best tankless water heater for you.

The build quality is unparalleled to none. It is super easy to install if you know what you are doing. If not, you can always get an installer to get you going in no time. Once you install the unit, it will give you endless hot showers for many years to come. You can stay in the shower for hours and this unit will never run out of hot water.

It can produce a 58°F temperature rise at a flow rate of 1.5 GPM (enough for a single shower in colder climates). If you live in a warm climate, where the temperature of water entering the unit can be as high as 77°F, you can achieve a temperature rise of 30°F at a flow rate of 3.2 GPM (enough for two simultaneous showers). For those in moderate climates where inlet water temperatures can be around 62°F to 67°F, you can get a temperature rise of 43°F at a flow rate of 2.1 GPM (enough for a hot shower and one sink running at the same time).

The unit comes with a digital temperature dial which lets you adjust the temperature degree by degree, giving you ultimate control over the temperature you desire. It has a 99.8% efficiency rating. You will save a lot of money on your monthly water and energy bills.

Ecosmart is a well-loved name in the electric tankless water heater world and the Ecosmart 11 does not disappoint.

Click here to read the full review including information on installation, usage, features, and maintenance.

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#10 Noritz NRC661-DV-NG Natural Gas Indoor Tankless Water Heater Review

Rating: 4.8 Stars Out of 5 | Type: Natural Gas | Temperature Rise: 70°F Rise @ 3.3 GPM, 60°F Rise @ 3.8 GPM, 50°F Rise @ 4.6 GPM, 40°F Rise @ 5.8 GPM, 30°F @ 6.6 GPM | Price: Click For Today's Best Price

 

Noritz-NRC661-DV-NG-Tankless-Water-Heater-ReviewThe Noritz NRC661-DV-NG is an indoor, natural gas, whole house tankless water heater with a peak flow rate of 6.6 GPM. This unit can supply hot water for a family of 6 with 3.5 bathrooms. It has enough power to supply enough hot water for 3 simultaneous showers depending on the flow rates of the shower heads and how hot you like your showers. In the winter months, it will provide hot water for 2 simultaneous showers.

With this unit, two people can be taking a steamy hot shower at the same time while the washing machine is also drawing hot water. This makes it a more than adequate hot water heater for the average home.

It has a peak flow rate of 6.6 GPM at a temperature rise of 30°F. If you need hot water at higher temperatures, the unit can produce a 70°F temperature rise at 3.3 GPM.

This unit is a condensing heater with very high efficiency. The higher price is well worth the money when you realize that the cost of installation is low as you don’t need expensive venting. This unit will use a PVC instead of the more expensive stainless steel venting required by low-cost non-condensing heaters.

I have spent hundreds of hours researching tankless water heaters for clients and I have yet to come across a single complaint about this water heater. The build looks and feels solid. The performance is excellent. It is highly efficient which takes over 50% off your current water and gas bills.  The cost of installation is low compared to cheaper models of tankless water heaters.

I would put this unit at number 1 on my list if not for the higher price. But if you have the money to invest in a tankless water heater for your home, I highly recommend this unit. Follow the maintenance instructions and you’ll have an endless supply of hot water for several years to come.

Click here to read the full review including information about installation, usage, maintenance, and warranty.

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Types of tankless water heaters

Tankless water heaters can be classified as gas powered or electric powered. The gas powered models are either powered by natural or propane gas. Each type of heater has its pros and cons. There are no clear “advantages” of one type over the other. However, each type might be more suitable to a specific kind of application. One such example is that gas powered tankless heaters might be more suitable for people living in colder climates than electric powered heaters. You’ll find that gas-powered heaters are more effective at providing consistent hot water during the winter months. I break down the main differences between gas-powered and electric powered tankless water heaters in the table below.

Electric tankless water heater vs Gas powered tankless water heater

 

Item
Electric Tankless Water Heaters
Gas-Powered Tankless Water Heaters
Initial Cost
Less Expensive
More Expensive
Running Costs Per Month
More Expensive
Less Expensive
Efficiency (Energy)
More Efficient
Less Efficient
Water Needs
More suitable for low to moderate water needs
Some models are excellent for high volume water needs
Installation
They are easier to install
They are more difficult to install
Power Needs
Needs up to 240 Volt electricity supply
Needs a natural gas or propane line
Climatic Conditions
Does not function as efficiently in winter as it does in other warmer conditions
It works efficiently in cold or warm conditions
Maintainance/Servicing
In general, less maintenance work required
More maintenance work required in general
Expected to Last
20 to 25 years life expectancy
20 to 25 years life expectancy

 

Tankless Water Heater vs Traditional Water Heater

I compare the main differences between tankless and traditional heaters. Tankless water heaters do have a higher initial cost when compared to traditional heaters. However,  once installed, it provides monthly energy savings which makes it much cheaper in the long run. Not only do you get lower monthly energy bills but tankless heaters also last about twice the lifespan of traditional heaters.  I understand why more of us and businesses are making the switch to tankless. This type of heaters also requires less maintenance once you’ve got it going. Both traditional and tankless heater advocates have arguments as to why their type of heater is the best. But in my experience and after talking to so many other users, I can only conclude that the benefits of tankless heaters far outweigh any negatives.

I have created the table below to compare tankless water heaters to their traditional tank counterparts.

 

Item
Tankless Water Heaters
Traditional Tank Water Heaters
Initial Cost
More Expensive
Less Expensive
Running Costs Per Month
Less Expensive (Up to 25% lower than traditional heaters)
More Expensive
Installation
Depending on the type or model of the heater, it may be more difficult to install. But most are easy to install
Generally much easier to install
Power Needs
Some tankless water heaters require additional electrical upgrade work to be done on the premises
Works with most existing electrical lines
Maintainance/Servicing
In general, less maintenance work required but some gas powered tankless heaters require an annual inspection
More maintenance work required in general but easier to maintain
Expected to Last
20 to 25 years life expectancy
10 to 15 years life expectancy

Who Needs a Tankless water Heater?

At this point, you might be wondering: “Do I even need a tankless water heater?” If you are an individual or a business planning on using large amounts of hot water over a long period of time, then a tankless water heater might be your best choice. This type of water heating device is also suitable for those of us simply concerned about the environment.

I want to present a couple of examples of individuals and businesses that will benefit from using tankless water heating systems on their premises.

Businesses that will Benefit from using tankless water heaters

If you are in the hospitality industry, you need to consider switching to this type heating system. Basically, if your business caters to customers that need to take repeated hot showers, you should consider making the switch. The savings you can make on your energy bills are huge.

Also, if you plan on building an apartment complex, you’ll benefit greatly from installing tankless water heaters instead of traditional heaters. Some models can supply hot water to more than one unit. Another benefit is that these types of heaters can be installed outdoors which gives you easier access for maintenance and repairs. Because tankless water heaters require less maintenance, you’ll also save money on maintenance.

Basically, if you run a business that uses a lot of hot water, a tankless water heater may be a far more efficient water heating solution to a traditional heater. There are units that supply water to multiple faucets and there are small units that supply hot water to a single faucet. If space is a problem for you, then tankless is the way to go. The initial cost might be higher but the savings you make in the long run far outweigh any benefits of using a traditional heater.

Individuals who should consider using a tankless water heater

Individual homes with large families living on the premise will benefit greatly from installing a tankless water heater system. The higher than average hot water needs mean you’ll benefit from huge monthly savings on energy costs in the long run.

This system of heating water can also benefit individual families that plan to stay in their current residence for an extended period of time. If you plan to stay at our current home for a period of more than 5 years, then the tankless solution is ideal for you. It may be more expensive to install but the long term savings will make sense in the end. Because of the higher initial cost, it may not be the best solution for you if you only intend to stay at the location for a short period of time.

What Size Tankless Water Heater Do I need?

Your hot water usage needs and the temperature of the environment are important factors to consider when determining what tankless water heater size you need to purchase.

To determine your hot water usage needs, you need to determine the flow rate of the devices and outlets that will use the hot water from the heater.

Step 1: Determine Flow Rate. (Flow rates of common home applications are listed in the table below). The first step is the find the water flow rate of the faucet the heater will serve. If the heater is going to provide hot water for only a single faucet, then use the flow rate of that single faucet. If the heater is going to provide hot water for an entire apartment or premise, you need to add the flow rates of the individual faucets and appliances such as washing machines and dishwashers. The flow rate is measured in gallons per minute (GPM).

For example, let’s say you are going to simultaneously run hot water to a faucet with a flow rate of 0.75 GPM and a shower with a flow rate of 2.6 GPM. In this case, you’ll need a tankless water heater with a flow rate of at least 3.26 GPM. In most home applications, you’ll run hot water to only one appliance or faucet at a time. At most, two faucets or appliances at a time. In my experience, most individual residential applications require a tankless heater with a maximum flow rate of 10 GPM. If you can invest in a heater with a higher flow rate, there’s no reason not to. Even a 3.5 GPM heater will suffice if you do not use more than two appliances or faucets at a time.

Read the following resources on how to determine flow rates for outlets and appliances in your home.

http://www.premierwatermn.com/flow-rates-achilles-heel-water-system/
https://www.energy.gov/energysaver/sizing-new-water-heater

Typical Flow Rates of Home Water Fixtures

 

FIXTURE/OUTLET
AVERAGE FLOW PER MINUTE (GPM)
AVERAGE TEMPERATURE
Bath Tub
4.0 GPM
102°F
Shower
2.5 GPM – 3.0 GPM
104°F
Washing Machine
2.0 GPM
120°F
Dishwasher
1.5 GPM
110°F
Sink (Kitchen)
1.5 GPM
110°F

 

Step 2: Temperature rise calculation: First determine the average temperature of ground water entering your home from the water company. You can call your water company for this information. But in general, the temperature of tap water is 50°F. The temperature rise is the difference between the tap water temperature and your desired hot water temperature. In most applications, tap water entering the heater will be heated to between 105°F to 120°F. The temperature rise will, therefore, be 70°F (120°F – 50°F).

Step 3: Determine the heater size you need: To determine the tankless water heater size you need, use the flow rate you need and the temperature rise required. Tankless heaters are rated by how many gallons per minute can be raised 70°F.

For example, your average hot shower temperature will be between 104°F and 106°F and have a flow rate of 2.6 GPM. Let’s say your incoming tap water temperature is 40°F. Let’s assume you want to produce enough hot water for two showers simultaneously. The combined flow rate of two showers will be 5.2 GPM. You’ll need a temperature rise from 40°F to105°F, which is equal to 65°F. So you need a tankless water heater that is capable of raising water temperature 65°F at a flow rate of 5.2 GPM.

Note: Gas powered heaters often cause a higher temperature rise per GPM compared to electric tankless heaters. Tankless water heaters can be whole house heaters that supply hot water to the entire house or a single application (point of use) heaters that supply hot water to one or two faucets or appliances. In my experience, it is sometimes better bo buy two point of use heaters instead of a whole house heater.

Click here to read my comprehensive guide to tankless water heaters

Tankless Water Heater Pros And Cons

 

Pros
Cons
 You can get a rebate from the Federal Government for making the switch to tankless
 Initial cost of switching to tankless is much higher than traditional heaters
Provides endless and constant supply of hot water
 If the heater is located far away from the outlet, it might take a while for hot water to get to it
Tankless hot water heaters can last up to 10 years longer than traditional heaters
 Installation might require that additional electric circuit work be carried out
Since water is heated on demand, tankless water heaters are much more efficient because there is no standby heat and energy lost
 The system only starts heater water when the flow rate reaches 0.5 GPM.
Electric tankless water heaters do not produce harmful greenhouse gasses
You might run-off a little bit of cold water while waiting for the hot water to come through.
Tankless water heaters require less space than traditional heaters. You may be able to install them in a closet without taking up much space
You can save up 25% on your monthly energy bills
Some tankless heaters can be operated with a remote control
 Tankless heaters do not store water, therefore, eliminating the risk of flooding.

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