Ok. At this point, you’ve probably heard about the advantages of tankless water heaters.
You get endless hot water with slashed energy costs from a system that takes up less space and lasts much longer than traditional conventional storage tank water heaters. It’s more environment-friendly and you’re never wasting energy by heating and reheating the same water.
Whether you’ve got a 3-bath home or a small RV, the question becomes, how do you go about getting the best tankless water heater for my needs?
Tankless.Review can help you select the best water heater.
On this website, we’ve covered the best residential tankless water heaters on the market, including natural gas, propane, and electric models. According to numerous reviews, most of these water heaters are best suitable for mid-size homes or high-demand households in warmer and moderately warm climates. For high-demand houses in the north, we reviewed special models with high GPM and BTU rating. We also included electric tankless water heaters for small houses, apartments, condos and low-demand households in general.
Being the #1 most popular selling water heaters brand, Rinnai is very well known in the US and Canada. It provides some of the best performing and the most efficient tankless water heaters on the market.
Rinnai RUC98in Performance Table
Temperature rise/Groundwater temp
Max flow rate (GPM)
That’s why Rinnai RUC98iN Ultra Series takes its first place in our tankless water heater rating.
This indoor unit is available in two options: natural gas or propane.
The condensing technology makes this tankless one of the most efficient models on the market. The Energy Factor (EF) of this model reaches as high as 0.96 and UEF rating is at 0.92. It means that for every dollar you spend on gas, you get 96 cents worth of on demand hot water. Pretty green, right?
You save water. You save energy. You save money.
Some of the owners we interviewed for our water heater reviews reported a significant drop in their energy bills.
Mrs. Widule is a proud owner of Rinnai RUC98iN. She agreed to share her personal review
We’ve had this unit installed for 2 years in our 2500 sq home with 3 baths and a family of 6. Works flawlessly. The only thing that’s bothering me a little is you do have to wait 5-10 sec more for hot water. But I believe a recirculation pump can solve the delay problem.
Also, we live where the ground water temp is at 50 degrees or so which limits the flow rate of the system to 5-6 GPM in cold months. At worst, it may limit how fast I can fill the tub, but it doesn’t prevent operating multiple showers.
Rinnai RUC98iN can provide astonishing 9.8 gallons per minute and that’s why it’s best suited for big families of 4 to 6 persons, or large homes, or houses with a lot of hot water appliances. With 9.8 GPM, you can use three showers, washing machine and kitchen sink all at the same time!
It has a different max flow rate for different temperature rise. To see yours check out our sizing chart. Also, make sure you have the needed BTU for your water flow rate.
Smaller households may not need the power of such a big on demand tankless water heater. If the water flow rate in your house or apartments does not exceed 6 GPM, we recommend a cheaper alternative – Rinnai V-Series. Follow the link and read the verified reviews.
Rinnai RUC98IN has two venting options: concentric and twin pipe PVC. Which is very convenient for installation, since you don’t need an adapter.
The installation process is pretty straightforward with detailed documentation. So you won’t have any problems with that. You can install it all by yourself and it wouldn’t violate the 12-year heat exchanger warranty, 5-year parts, and 1-year labor insurance.
If you’re not comfortable with installing, you may be interested in top local plumbing professionals in your area.
The warranty for the tankless unit is provided by Rinnai, not your local supplier or the installation company who may charge you more than it really costs. So instead of overpaying them, better buy the unit from Amazon and get the warranty from installation company on their installation work (not the unit itself). You can save several hundred dollars on it.
More PRO TIPS:
Check if you’re eligible for rebates in your area. You may save even more (up to $500!).
One of the most efficient models on the market with EF of 0.96
It has a by-pass thermal control system which reduces the time before you get hot water.
Valves for flushing included (saves you a couple of hundreds of dollars)
It’s Energy Star certified so you can get a $500 rebate at your local gas company.
Very convenient venting for concentric and PVC pipes
Some owners report a slight dip in water pressure when using more than two showers.
It still needs some time to get to hot water after the tap is opened (may be solved by installing a recirculation pump)
It’s pretty expensive, although it buys itself in 5-6 years through savings on energy
If only this model was cheaper, we’d give it the first place in our rating. Rinnai RUR199iN is from the same Ultra Series line as Rinnai RUC98. Basically, it’s the same ultra-efficient tankless water heater but the maximum flow rate here is 11GPM. You can read the previous review and it wouldn’t be much different than this model.
It has only two differences, but those are significant enough to get a separate second place among all our tankless water heater contestants.
The first and most important difference is that the RUR199iN model has a built-in recirculation pump. It eliminates a significant disadvantage of the previous model. You don’t have to wait for hot water to get to your faucets. You get instant hot water.
Tankless water heaters instantly heat the water but then it needs to get delivered to the fixture. For instance, your master bathroom is 80 feet from the heater. The unit fires up as soon as you open the tap, but you’ve got to evacuate all that cold water that’s in the line.
With other models, you’d have to install an additional recirculation pump (which usually needs a dedicated return line), but with the Rinnai RUR199iN Ultra Series model hot water is instantly available in showers, sinks and kitchen appliances like washing machines or dishwashers. Because the pump is built in the tankless. You can push a button on the side, or use a motion detector, or a timer, or an app (Rinnai has several options) and as you walk into the master, the cold water circulates back at the tank and you get instant hot water in your shower. The good thing here is that you don’t have to drain that water anymore, it’s going back to the cold line.
You’re going green by saving more water
You’re saving more energy, since it has an astonishing 0.96 EF rating, meaning that for every dollar you spend on propane or gas, you get 96 cents back in hot water (compare it to tank water heaters where you get only around 65% converted to hot water).
You’re saving money because you spend less on utility costs related to gas and water usage.
You’re getting ENDLESS and INSTANT hot water.
The second difference is the price. Rinnai RUR199IN is several hundred bucks more expensive. You can check the current price on Amazon by following the button below and compare the price to RUC98IN.
If you’re willing to pay the extra dollar for convenience and instant hot water on demand without waiting (sometimes up to 30-40 seconds), Rinnai RUR199IN is the way to go. It’s flawless. 20+ owners that we interviewed for these reviews can vouch for that. Plus you can read all Amazon reviews for this model by following the link below and exactly the same but a bit older version Rinnai RUR98iN here.
If you think that paying several hundred dollars just for the recirculation system is too much and you can wait a few seconds, Rinnai RUC98 is your best choice.
Built-in recirculation system, no “cold water sandwich” problem
A digital controller that allows to schedule the recirculation to align with usage patterns
Multiple venting options
Can be used with or without a dedicated recirculation line
Rheem is one of the most trusted American brands in the water heaters industry. We couldn’t make a TOP list without mentioning it.
We chose Rheem RTGH-95DVLN for its time-tested great reputation as a reliable workhorse for thousands of Americans. It is reported by the owners that Rheem RTGH-95DVLN perfectly does its main job of heating water without any significant issues.
Now let’s get to the technicalities. This model comes in two options: indoor and outdoor. Both require a min. 11,000 BTU and can handle up to 199,900 BTU.
It shows 94% efficiency due to a stainless steel condensing heat exchanger (that’s how the heating element is called). It’s designed for both large and mid-sized homes, providing up to 9.5 GPM flow rate.
You would be surprised that such small and compact tankless water heaters can supply hot water to a big family of 4 to 6 members. The owners say that they tried using two showers, a whirlpool tub, and a kitchen sink all at the same time and the temperature never dropped.
It’s easy to install thanks to two PVC pipes direct venting system. You don’t need expensive stainless steel vent piping.
Some owners said that they experience some noise. It may happen because of improper installation. If you install the intake and exhaust pipes too close to each other, the intake may start sucking exhaust fumes causing the fan to run at its full capacity. It tried to clear the intake. So be careful about installing the unit. Or get professionals to do the job.
Endless and consistent supply of hot water
Vent system designed for PVC pipes
Cold water sandwich problem (if used without a recirculation pump)
Up to this point, we’ve only reviewed gas/propane tankless heaters. They have great performance and a high flow rate. They’re very efficient and saves you money on energy costs for water heating. They may be used in every type of household, whether it’s a large 3-bathroom house with a big family enjoying a hot shower in all three bathrooms simultaneously or a mid-size house in the cold northern states where a couple wants to have the luxury of endless hot water on demand.
But not everybody needs that high performance in their apartments, or condos, or RVs, or trendy tiny houses… You get the point. $3000+ in upfront costs for a 10 GPM tankless unit that will be used for heating water for one shower during all day might be an overkill.
So Rheem RTEX-13 comes to the rescue. It’s an electric tankless water heater for single point-of-use or multiple applications. It’s best suited for apartments or small houses with low to medium hot water demand, where just one or two people are using hot water appliances. It’s also great for offices.
Rheem RTEX-13 is very easy to install, just follow the manual and you’ll get along.
For Rheem RTEX-13 you’re going to need to have 1 x 60 amps power breakers. 6 AWG wire size is recommended. If you’re not familiar with wiring details, consider getting a quote from professionals.
It is one of the several units from the Classic Series. If the maximum of 3.8 GPM in Rheem RTEX-13 is not enough, you can choose a different option. The model with the highest performance is Rheem RTEX-36 which, according to Rheem, can provide impressive for an electric tankless water heater maximum of 8GPM, if you live in the south. The lower the temperature of the groundwater in your location, the lower the flow rate will be. Although the manufacturer claims the maximum flow rate is that high, the actual one will probably be around 3 GPM for RTEX-13 and around 6 GPM for RTEX-36.
If you want to use low flow rate models like Rheem RTEX-13 in your house, but you’re afraid that they won’t be able to handle your hot water demand, consider installing low flow showerheads and aerators on as many fixtures as possible. It will reduce your actual flow rate without losing the pressure. And with less GPM demand you’ll need smaller and cheaper tankless water heater.
Very easy to install
Good choice if you’re on a low budget
It has compact sizes and could fit probably everywhere
Great value for the money
One unit can’t supply the whole house with hot water (you can buy several units though)
Without recirculation pump, it has a cold water sandwich
This is yet another electric tankless water heater from a German brand Stiebel – Stiebel Eltron Tempra Plus 36 kW. This is a great alternative for houses with no gas lines or if you just prefer electric water heaters.
Tempra Plus series come in different sizes ranging from models with 1 GPM flow rate to 8 GPM in perfect conditions. Maybe in a lab 🙂 But in real life with the temperature rise of 50-60 degrees this model will provide a stable flow rate of 4 to 5 GPM of endless hot water.
If you haven’t had electric tankless heaters you will probably need to make some adjustments in your electric panel. It requires 3 x 50 amps breakers and 3 x 6/2 AWG cables.
This model can potentially use 150 amps, so make sure you have enough capacity
Stiebel Tempra Plus 36 is really tiny and can fit just about everywhere.
When we prepared our tankless heater reviews, the most common question about this unit was if it can fill a bathtub with hot water. The answer is clear YES. 4-5 GPM is definitely enough for a bathtub. Moreover, we interviewed some owners from Missouri (with an average groundwater temp around 52-57 degrees Fahrenheit) and they’ve said that it could easily supply a house with 2 bathrooms, laundry, and a kitchen with hot water. With the air temperature in the 60-65 degrees, it was able to supply 2 showers running at the same time. There was some reduction in pressure though.
It’s great for large homes in warmer climates and for smaller homes in the northern states.
Relatively low price
It has very convenient automatic controllers that adjust the pressure and temperature to meet the demand when several fixtures use hot water.
Due to small sizes, it saves a lot of space and can be installed near the point of use. It’s also very quiet, so it wouldn’t make any anoint noise
It requires NO venting
Since it’s an electric water heater, it may be difficult to install if you had no previous experiment
In cold climates, it performs much worse and consumes more energy. During dead cold winter when the groundwater temperature is below 50 degrees it can barely produce 3.5 GPM
This is probably the best electric tankless water heater for medium-sized households. For such a low price it provides an astonishing real 4.5 GPM flow rate. In northern states, it can achieve up to 2.3 GPM. And that’s not just naked specs. The owners we interviewed and people on Amazon with verified purchases also say it can handle that amount of hot water without losing much water pressure.
It requires two 40 amps breakers and 2 x 8 AWG wires and a 240 V circuit.
If you live in the southern states you can be sure that this unit can easily handle a mid-size household with two showers plus maybe a laundry used at the same time. But as always, it all depends on the temperature of the incoming water. The lower the temperature, the more the tankless heater has to work, the lower the flow rate it will be able to provide hot water at the set temperature.
DISCLAIMER: We’re absolutely neutral in our reviews. We do not accept free items or payments for our reviews. We may earn a small commission from any purchase you make, so we’re not biased towards any specific brand. And we genuinely want to give you the most comprehensive reviews of existing tankless water heaters models and brands so you make the choice you wouldn’t regret.
So how good are tankless water heaters that we chose for our list? We have several criteria for our water heater reviews and rating, which include:
Brand reputation among plumbers, HVAC professionals, and tankless water heaters owners
We evaluated how convenient are the exclusive features that some brands and models offer
Prices as compared to other brands
In total for our website, we evaluated over 120 models. We interviewed 4 plumbing professionals (including my colleague), and several owners, and created several lists of best water heaters for different needs. I guess professional plumbers and experienced owners are reputable enough source for our tankless heater reviews.
Things to consider before buying a tankless water heater
Tankless water heaters are available in many different sizes across all brands.
The biggest size you can have available for residential models is 199,000 BTU.
Above 200,000 BTU you’re going to need plumbing license called a boiler operator license
Determine your inlet water temperature in your location and the temperature rise
You want to be cautious about input water temperature in your area and overall water heaters capacity.
Let me explain…
The size of a tankless water heater that you need depends on the temperature of incoming water. If you live in the south, you’re going to have fairly warm water (around 50-60 degrees) going into your water heater.
Whereas if you’re building in Connecticut or Boston you could have 35-40 degrees water going into the water heater. So it has to perform a lot more work to get the water up to 120 degrees, which is your final output. Your tankless will have to work harder to heat your water because it requires a greater temperature rise.
The same unit in Texas would produce a greater flow of hot water than it would in Boston in the wintertime.
So if you live in cold areas of the country, you may get a bit lower max flow rate than it says in the specs. For example, the maximum flow rate for Rinnai RUR199iN in our table is 11 GPM. It means in northern states you’ll get around 6-8 GPM.
And If you live in the south, you may count the exact flow rate.
Because in a warmer climate your tankless water heater doesn’t have to work as hard because it requires a lower temperature rise.
You can just use the groundwater temperature map of the United States (or Canada) for reference. Find your groundwater temperature based on the color of your location. And compare the different models’ flow rates for your temperature rise.
Determine GPM (flow rate) needed
How many GPM tankless water heater do I need?
Once you determine your inlet water temperature, you need to figure out your gallons per minute (GPM) demand.
GPM demand is the sum of all fixtures’ flow rates that use hot water running at the same time.
You may use our GPM estimate chart to determine how many GPM you need for your house.
Simply add up all individual hot water appliances’ GPM. You’ll get your home maximum GPM.
Keep in mind that if you’re planning to use all of the appliances simultaneously you might need to overestimate the GPM if you don’t want to run out of hot water.
GPM CHART TABLE – Coming Soon
If you have a very large home, even really big tankless water heaters with a high GPM rate may not fit your requirements.
And even if the specifications say the unit fits you, you might not get instantaneous hot water because of the cold water sandwich. It means that you may need to flush all cold water before the hot water gets through the pipes to the fixture. And in big houses, it may take up to a couple of minutes. Endless hot water is not always instant hot water.
There are two ways to deal with the problem.
You can buy a tankless unit with a built-in recirculation pump, like Rinnai. Or you can buy an additional recirculation pump if the unit doesn’t have a built-in option.
Or you could buy an additional point of use tankless water heaters and install it under the sink or near the washing machine or dishwasher.
Now that you know how big your tankless should be, you may notice that there are many brands that manufacture tankless heaters. But how to decide which one to choose?
If you’ve asked different contractors, you know that every single one of them recommends different brands. And they make it even harder to choose.
We asked one of our experts. And here are a couple of insights he agreed to share with us:
Frank J. Cowles
Frank J. Cowles is a NY-based HVAC professional with 20+ years of experience in the industry
For many contractors, the brand they’ll recommend is based on what they can get parts and support for.
Myself – I prefer Rinnai and Bosch. Rinnai has people on call – even on weekends – to offer contractors support on troubleshooting. Bosch has higher efficiency and a more adaptive intelligence in their operating software than most. Are Navien, Nortz or the others bad units? No. Navien supports their products very well. The others vary based on brand.
In the end – buy your contractor. If you feel comfortable with him and know he’ll be their when you need him – go with the unit he recommends. One word of caution – beware of those that do not own or use a combustion analyzer. The 90%+ plus unit MUST be tested and tuned to run properly. Bosch has that as a internal function done as part of commissioning. Most other brands do not and will fail early if not commissioned properly.
Decide which power source you are going to use
There are three options on the market. And all depends on your current power source that you have.
Natural gas and propane water heaters are best for large homes or cottages as whole-house heaters.
Electric tankless water heaters and point of use heaters are best for small homes, tiny houses, apartments, condos or even RVs.
There are a few electric tankless water heaters options for the whole house though. They’re really good for houses where there’s no propane or natural gas available.
Additional requirements for electric units
Before choosing a tankless water heater find out if your home has the necessary electrical requirements to support the unit you need.
Since they have greater voltage requirements, you may need to have a qualified install upgraded breakers and thicker gauge wiring to handle an increase in power.
How many amps do you need?
What size breaker do I need?
What kind of tankless water heaters do I need? (by Power Source)
Condensing vs Non-condensing
There are really two types of gas tankless water heaters: condensing and non-condensing.
The non-condensing models are usually less efficient and across all manufacturers have around 0.8 EF
The condensing models are about 10% more efficient with around 0.9 EF rating.
EF or Energy Factor is the measurement for the energy efficiency of a water heater. The higher the EF of a water heater, the more efficient it is
If the unit has EF 0.8 and we translate it into dollars, that would mean that every dollar of gas you put into the unit, $0.8 are going to be transferred into the hot water, 20% are going to be lost in the atmosphere due to inefficiency.
Keep in mind that with the tankless heater we do not have stand by losses. They’re only going to heat up when the faucets are opened and there’s flow through the unit, which means it’s calling for the hot water.
If you compare this to the traditional tanks, tankless heaters are also 15%-20% more efficient than a standard tank-type unit.
So you’d ask, why would I choose a non-conditional tankless water heater over the conditional one? Let’s look at the pros and cons of each type.
Non-condensing tankless water heaters
They are based on very old, proven, and mature technology. They have fewer parts involved, there’s less to go wrong with them. It also costs less initially to install the non-condensing unit. And you don’t really have to worry about disposing of the condensate.
But there are also some downsides. Especially with the units for indoor installation. They require a stainless steel vent pipe. Because the condensation that might occur in the pipe is very acidic and because the flue gases are pretty hot (up to 300 degrees) you’ve got to use expensive piping.
Condensing tankless water heaters
Now with the condensing models, you don’t have this problem. The pipes are going to gather water. And as it gathers water and condenses that water that’s how it rings out the extra efficiency. But it also means that it has to have the place that it can drain to.
The big beauty of the condensing tankless water heaters is that you can vent with PVC pipes. You can plug in a standard and inexpensive PVC in the air intake. The gas that’s going to come out of the heater is only 100 degrees, so you can use a standard PVC pipe on the air exhaust too.
So condensing water heaters are more efficient and PVC venting can be a big deal. Because you can seal around the heater. It’s very good from the air sealing standpoint because it means you can mount a heater in a laundry room or in the basement. You just plug in the pipe, spray foam and caulk around that and seal it really well so that it doesn’t have any air leakage.
Costs and prices
Tankless water heaters are usually more expensive than tank-type water heaters. But it’s a great investment if you count the costs over time.
They’re available in a wide range of prices. It really depends on the type and size of a tankless water heater. The bigger you choose, the more expensive it will be. You really pay for what you get.
If a tankless unit seems too expensive for you, it might be because it already has a special feature, like a built-in recirculation pump or smart technology. You can choose a cheaper option, but are you really sure you won’t pay more in the future?
For example, a built-in recirculation pump solves the problem of a cold water sandwich and supplies you with instant hot water. It decreases the amount of draining water and reduces your water and energy bills.
A few thousand dollars right out of the pocket is never cheap. But it’s not that big of a deal when you compare it to overtime cost of having two or three tank water heaters.
The maintenance cost depends on the water. The harder it is the more maintenance it’s going to require.
If you use well water and you have a family of 3 to 5 kids and you use hot water a lot, you’d probably need to flush your tankless once a year.
It’s relatively easy. You just get a solution pumped through the burner system. It’s going to remove all that calcium deposits from hard water.
If you have 2 to 3 people in your house, you’d need to do the procedure once every 2 to 3 years.
You can make it work longer without flushing the system if you use a water softener system or you just have soft water. This way you may never even need to flush the water heater.
What are the advantages and disadvantages of a tankless water heater?
Endless hot water
When the demand is high, tank water heaters may run out of hot water, leaving you in the cold. But tankless water heaters heat water as it goes through the pipes, giving you an endless supply of hot water for the whole family.
So if you like those 30-minutes long showers, tankless water heaters are your best choice.
Higher quality and longer-lasting product
Tankless water heaters usually last twice or even three times longer than your typical tank water heaters if you use a water softener or just soft water. The average lifespan of a tankless unit is around 20-23 years.
And as it’s been mentioned, you get an endless supply of hot water and reduced water heating costs for basically the same amount of money.
Unlike big tank water heaters, tankless units do not take a lot of space. You just mount a little box on the wall or under a sink and you’ve plenty of space left for your utilities.
A tank may heat and reheat the water even when you’re not at home.
Tankless water heaters operate strictly on-demand. This means you only heat water when you need it. When you don’t need it, the unit does not consume any energy.
And that saves you money!
Of course, if you don’t have a large house or several kids who use the hot water heater a lot, you may not see a ton of money saved in your natural gas bill. But it will still go lower! Because you are only using hot water when you wash dishes, clothes, or take a shower. You don’t have it all on all the time. And you don’t have a huge 50-60-75 gallons tanks constantly being heated up.
The savings may not be big month to month, but over time you’ll see how a tankless water heater is a great investment of your money.
Higher upfront cost
Tankless water heaters are more expensive to purchase than tank-type water heaters.
That’s a fact.
But what if you consider that an investment for a stable system that supplies you with endless hot water, reduced energy costs, longer-lasting equipment and more? Yes, that looks a bit more tempting.
But that’s exactly the case!
Just a minute of math. Traditional tank water heater’s lifespan is around 13-15 years max, while the “luxury” tankless water heater can serve you for about 25+ years.
Now, tank water heaters cost $1000-1500 on average, while tankless units may cost you about $2500-3500. So it turns out that the average cost per year is about the same over time.
You can include here the water heater installation costs. It means changing the old pipes and venting. It may cost you a couple of hundreds of dollars. But the good thing is that you may get a rebate of up to $500 through the gas company for energy efficiency. So, it makes it even.
Tankless water heaters require electricity. Even with gas or propane units, they need electricity both for circuitry and to fire up the burner. So if your power goes out, you won’t have any hot water.
If you’re using a tankless, it’s great to put it inside the air-conditioned envelope of your house so you’re not worried about freezing.
A great place to put an indoor tankless water heater is a garage or basement. Especially if you’re in the north and garage and/or basement is heated.
You just run the vent pipe through the wall and it will bring in the burner combustion air and then exhaust that air from the burner combustion process. It’s not going to mix with your house air. The venting and plumbing will be within air-conditioned space which means no freezing issues.
However, in the south, you might have an exterior-mounted tankless unit. It’s going to save up some space but you need to take a couple of extra precautions for freezing:
Make sure the power is on to the unit in freezing weather. It has an electric internal heater that allows to use it in relatively low temperatures. Depending on the model, it can work when it’s zero degrees outside. And don’t forget about the pipes that lead up to the tankless heater that are outside. You need to wrap them with insulation and put some heat tape as well.
The problem with tankless water heaters is that they require maintenance. We’ve covered this part when we discussed costs.
But here’s the good side…
Maintenance is VERY easy with modern tankless water heaters. Many of them have a little LCD screen where you can see the output temperature of the water. When something is wrong or broken, it shows an error code which you can google online, or call a plumber, or call the manufacturer. It’s really handy and you don’t have to worry about ANYTHING.
Low minimum flow rate
My clients almost never remember to pay attention to this parameter when they choose a tankless for their home. But it may become an issue for you. Especially in winter if you live in a colder climate region. The problem is that when the flow is too low, the unit may not be activated and you’ll get colder water. It’s almost never a thing for modern (and more expensive) tankless water heaters because their minimum flow rate is at 0.26-0.3 GPM. But if you choose to buy an older model you may end up with cold water when you want to wash your hands.