Best Whole House Tankless Water Heaters

10 Products Evaluated
32 Hours of Research
1 Experts Interviewed
79 Reviews Analyzed

Picking the right whole house tankless water heater is challenging:

You have to decide what’s the right power source (electric, natural gas, or propane), figure out the sizing of a tankless unit, and choose the best brand. And on top of that, you’d want the new tankless water heater to fit the tight budget.

Sounds familiar? Don’t worry, we’ve got your back!

In this article, we’ll help you to pick the best whole house tankless water heater. We’ve already picked the best options for all power sources, sizes, and even budgets where it is possible. You only need to pick the one that fits your needs.

Check out the table below and dive into the detailed reviews if you want to learn more!

Tankless Water Heater
Best For Large Homes
Rinnai RUR199i Whole House Tankless Water Heater
Best for Medium-sized Households
Rinnai RL75i Whole House Tankless Water Heater
Best Electric
EcoSmart ECO 27 Whole House Electric Tankless Water Heater
Rinnai RUR199iN Tankless Water Heaters, RUR199in-Natural Gas/11 GPM
Rinnai RL75IN Tankless Water Heater, Large, RL75iN-Natural Gas/7.5 GPM
EcoSmart ECO 27 Electric Tankless Water Heater, 27 KW at 240 Volts, 112.5 Amps with Patented Self Modulating Technology,White
Power Source
Natural Gas/Propane
Natiral Gas/Propane
Electric
Size
3 to 4 bathroom house
2 bathroom house
1 bathroom house in cold climates; 2 bathroom house in warm climates
Specs
Indoor installation; Flow rate: 11 GPM; Efficiency (UEF): 0.94; 199K BTU
Indoor installation; Flow rate: 7.5 GPM; Efficiency (UEF): 0.82; 180K BTU
Service requirements: 113 amps (3 double pole x 40 amp breakers); Flow rate: 5 GPM; Efficiency: 99.8%; 27kW at 240 Volts
Best For Large Homes
Tankless Water Heater
Rinnai RUR199i Whole House Tankless Water Heater
Rinnai RUR199iN Tankless Water Heaters, RUR199in-Natural Gas/11 GPM
Power Source
Natural Gas/Propane
Size
3 to 4 bathroom house
Specs
Indoor installation; Flow rate: 11 GPM; Efficiency (UEF): 0.94; 199K BTU
Best for Medium-sized Households
Tankless Water Heater
Rinnai RL75i Whole House Tankless Water Heater
Rinnai RL75IN Tankless Water Heater, Large, RL75iN-Natural Gas/7.5 GPM
Power Source
Natiral Gas/Propane
Size
2 bathroom house
Specs
Indoor installation; Flow rate: 7.5 GPM; Efficiency (UEF): 0.82; 180K BTU
Best Electric
Tankless Water Heater
EcoSmart ECO 27 Whole House Electric Tankless Water Heater
EcoSmart ECO 27 Electric Tankless Water Heater, 27 KW at 240 Volts, 112.5 Amps with Patented Self Modulating Technology,White
Power Source
Electric
Size
1 bathroom house in cold climates; 2 bathroom house in warm climates
Specs
Service requirements: 113 amps (3 double pole x 40 amp breakers); Flow rate: 5 GPM; Efficiency: 99.8%; 27kW at 240 Volts
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Here’s the list of the best whole house tankless water heaters to consider this year:

1. Rinnai RUR199iN Whole House Tankless Water Heater

Rinnai RUR199iN
Rinnai RUR199iN Whole House Tankless Water Heater:
  • Fuel Type: Natural Gas
  • Efficiency: 0.93
  • Product dimensions: 22.1 x 14.8 x 33.9 inches
  • Flow rate: 11 GPM
  • Energy Star® certified
Read Verified Customers Reviews

Rinnai RUR199iN is the number one tankless water heater in most of our ratings. And that’s especially true for the whole house options.

It is available in two options: natural gas and propane. Both provide similar performance in terms of flow rate.

Rinnai RUR199i is the largest residential tankless water heater out there, and it can easily supply the hot water for a house of almost any size. Even if it is a 4 bathrooms house. With a flow rate of up to 11 GPM, it can handle even the super heavy demand during the peak time in busy households. It can provide up to 11 gallons of hot water per minute, which equals 4+ showers running all at the same time!

Of course, that’s not always true as the performance and the flow rate heavily depends on the groundwater temperature. In colder climates, that number can go down to 6 GPM of consistent unlimited hot water but that’s still 2 showers using hot water simultaneously and one fully open faucet. During a freezing winter. Not bad, huh?

And on top of that unbeatable performance, Rinnai RUR199iN has a built-in recirculation pump (hence the price) and some other fancy and useful features. The built-in recirculation pump ensures you have really instant hot water access from any part of the house at any given time. You don’t have to wait for hot water to travel through your plumbing system through the whole house to your shower. And a special technology (called ThermaCirc360) ensures that you can enjoy instant hot water even in houses without a dedicated return line.

If you’re not comfortable burning some gas all day long to have the hot water available all the time, you can easily set the daily timer for the busiest time of the day and Rinnai RUR199i will pre-heat the water and deliver it to your showers, faucets, and appliances when you need it! So that you can enjoy the luxury of having instant and endless hot water without experiencing the so-called “cold water sandwiches” when there is cold water in the system and you need to wait before it drains out.

And if that’s not enough, Rinnai RUR199iN offers WiFi control and monitoring module. It allows for control of the whole house tankless water heater remotely. You can use Rinnai’s native app or connect the unit to the Amazon Alexa, Google Home, or Smart Things and schedule the water heating as a part of your morning routine!

We recommend buying this whole house tankless water heater if you want to get the most powerful, most technologically advanced, and reliable unit. It will definitely satisfy all your needs.

2. EcoSmart ECO 27 Whole House Electric Tankless Water Heater

Ecosmart ECO 27 - Best Whole House Electric Tankless Water Heater
EcoSmart ECO 27 Whole House Electric Tankless Water Heater:
  • Electrical service requirements: 113 amps (3 double pole x 40 amp breakers)
  • Efficiency: 99.8%
  • Product dimensions: 17″H x 17″W x3.75″D
  • Flow rate: 5 GPM
  • Activation Flow Rate: 0.25 GPM
Read Verified Customers Reviews

Ecosmart ECO 27 is our #2 choice. It’s one of the best whole house electric tankless water heaters out there and you’ll soon learn why!

In general, I don’t like recommending electric tankless water heaters as whole house options because they require a lot of electric power and they still don’t provide the same level of performance. Especially in colder climates. If you live north of Colorado, I highly recommend considering a natural gas tankless water heater like the Rinnai RUR199iN that we’ve reviewed above or some of the more affordable options below.

But if you live in the states with warm weather, Ecosmart ECO 27 or its more powerful versions like ECO 36 would do a great service providing unlimited hot water.

Ecosmart ECO 27 is capable of heating up to 6.5 gallons of water per minute which equals to about 2 showers consuming hot water simultaneously and there’s some “free” GPMs left.

Again, that perfect performance is only possible if you live in places with warm climates somewhere between Florida and Texas, or in the south of California. The colder the inlet water is, the lower the flow rate is going to be. If you’re asking what size tankless water heater you need, please read our sizing guide.

Quick guide: open the USA map on Google or Apple Maps, divide the country in half just in the middle. If you live in the lower (southern) part, you’re ok with a whole house electric tankless water heater. If you live in the northern (upper) part, I do not recommend buying a single whole house electric tankless water heater. Consider picking a natural gas unit or go with a regular tank unit with a couple of additional point of use electric tankless water heaters like ECO 13.

One thing that make electric tankless water heaters stand out is their efficiency. At 27kW Ecosmart ECO 27 is 99.8% efficient! It means that you get 99.8 cents worth of electricity spent on heating the water for every dollar you spend.

Now if it’s cheaper than a gas version is another question. It depends on the price of electricity vs gas in your place. Most of the time gas is a cheaper option long term. But if your home is only set up for electric appliances, converting to gas would cost you some additional several hundred dollars or more. You might want to stay with the electric options. Besides, electric tankless water heaters have much lower initial purchase costs.

To install Ecosmart ECO 27 you need to have about 115 amp service available and enough place for 3 double pole breakers.

Overall, it’s a great electric whole house tankless water heater and we do recommend it if you know you need an electric one and you have at least 150 amp electric service (you’re not using all of it to heat the water, aren’t you?).

3. Stiebel Eltron Tempra 29 Plus Whole House Electric Tankless Water Heater

Stiebel Eltron Tempra Plus Whole House Electric Tankless Water Heater
Stiebel Eltron Tempra 29 Plus Whole House Electric Tankless Water Heater:
  • Electrical service requirements: 120 amps (3 double pole x 40 amp breakers)
  • Efficiency: 99.8%
  • Product dimensions: 4.63 x 16.63 x 14.5 inches
  • Flow rate: 7 GPM
  • Activation Flow Rate: 0.75 GPM
Read Verified Customers Reviews

Stiebel Eltron Tempra 29 Plus is another example of how good electric tankless water heaters can be.

It provides a similar level of performance as ECO 27. Meaning that at 6 GPM Stiebel Eltron Tempra 29 Plus can supply 2 showers running at the same time.

As with any other whole house tankless water heater, the colder the water coming into it, the more it has to heat it and the lower the temperature of the outcoming water is going to be. That means that the maximum flow rate is going to be lower for states with colder weather. As always, it all depends on the temperature rise. If you’re not familiar with the definitions and not sure how it all works, learn more in our sizing guide.

Stiebel Eltron Tempra 29 Plus draws up to 200 amp at the highest load. It doesn’t mean it always draws 200 amp though. Usually, it’s much lower. But you should be ready for it and make sure your electrical service can handle the load and other appliances.

Like the previous whole house tankless water heater, Stiebel requires a place for 3 double pole 40 A breakers in your electrical service panel.

The interface is very straightforward and easy to use. You can easily set up the temperature at any time.

Stiebel Eltron Tempra 29 Plus is also very quiet.

We recommend this tankless water heater for smaller homes with 1 or 2 bathrooms that have powerful enough electrical service to handle the possible 200 amp load.

4. Rinnai RL94e Whole House Tankless Water Heater

Rinnai RL94e
Rinnai RL94e Whole House Tankless Water Heater:
  • Fuel Type: Natural Gas
  • Efficiency: 0.82
  • Product dimensions: 14.02 x 10 x 22.99 inches
  • Flow rate: 9.4 GPM
  • Energy Star® certified
Read Verified Customers Reviews

Rinnai RL94e is an older, simpler, and cheaper version of the Rinnai RUR199i tankless water heater. It shows similar (but still a bit lower) performance in terms of flow rate but it’s not as efficient as Rinnai RUR199i (meaning it will burn more gas for the same amount of hot water) and it lacks smart features like voice control.

Other than that and a couple of other minor details, Rinnai RL94e is pretty the same as Rinnai RUR199iN but cheaper.

Rinnai RL94e is available in two options: natural gas and propane.

The maximum flow rate that Rinnai RL94e can provide is up to 9.4-9.8 GPM. It means that it’s a perfect tankless water heater even for a 4 bathroom house.

Keep in mind that this is the highest flow rate possible. In freezing weather it’s going to be lower, depending on the temperature of the inlet water. But still, to reach the peak performance you’ll have to use 4 showers all at the same time.

Rinnai RL94e can easily fill the tub, if that’s what you’re looking for.

RL94e is an outdoor version of the same model series. You can install it outside of your house which saves even more space inside. If you’re looking for the indoor version, check out Rinnai RL94i. The last letter (N or P) defines the power source. So N would be Natural gas, and P would be Propane.

Rinnai RL94e also has the recirculation technology which allows you to have the hot water pre heated when you need it.

Rinnai RL94e is a great whole house tankless water heater for a house of basically any size. If you liked the Rinnai RUR199iN but you thought it was too expensive, RL94e is a great alternative with similar performance for a much lower price.

5. Rinnai RL75i Whole House Tankless Water Heater

Rinnai RL75i
Rinnai RL75i Whole House Tankless Water Heater:
  • Fuel Type: Natural Gas
  • Efficiency: 0.82
  • Product dimensions: 14 x 9.3 x 23 inches
  • Flow rate: 7.5 GPM
  • Energy Star® certified
Read Verified Customers Reviews

Rinnai RL75i is a smaller indoor version of the previously reviewed RL94e. We’re not going to go deep into the details about it, since it has all the same features as the previous one. But if you’re looking for a more affordable option for a house with 2 bathrooms, that might be it.

Rinnai RL75i provides up to 7.5 gallons of hot water per minute which is enough for 3 showers using hot water simultaneously. Or if you have 2 bathrooms, let it be 2 showers and a fully open kitchen faucet, or any appliance.

Other than a lower flow rate and lower price, Rinnai RL75i is the same as the previous model.

6. Rheem RTG-95XLN Whole House Outdoor Tankless Natural Gas Water Heater

Rheem RTG-95XLN
Rheem RTG-95XLN Whole House Outdoor Tankless Natural Gas Water Heater:
  • Fuel Type: Natural Gas
  • Efficiency: 0.94
  • Product dimensions: 18.5 x 9.75 x 27.5 inches
  • Flow rate: 9.5 GPM
  • Energy Star® certified
Read Verified Customers Reviews

Rheem tankless water heaters are also great. Rheem RTG-95XLN managed to get in our list of the best whole house tankless water heaters and rightfully so! Let’s review some of its features.

First things first, Rheem RTG-95XLN can provide up to 9.5 GPM at a 0.82 efficiency rate. It’s about the same performance as the RL94e offers. Same flow rate, same efficiency.

But compared to the RUR199iN version, this Rheem is almost 10% less efficient, meaning it’s going to burn more gas for the same amount of water heated to the required temperature.

In other words, you’ll spend more on gas with Rheem RTG-95XLN than with Rinnai RUR199iN. And about the same amount compared to RL94e. Hope that makes sense 😀

Outdoor installation allows Rheem RTG-95XLN to save you more space which is very important in places where space is money. It also saves you money on installation and amount of work because it doesn’t require any venting.

We do recommend buying this tankless water heater if you’re not happy with the previous models and the technical specs satisfy your needs.

7. Takagi T-H3-DV-N Natural Gas Indoor Tankless Water Heater

Takagi T-H3-DV-N
Takagi T-H3-DV-N Natural Gas Indoor Tankless Water Heater:
  • Fuel Type: Natural Gas
  • Efficiency: 0.93
  • Product dimensions: 10.75 x 17.75 x 22.5 inches
  • Flow rate: 10 GPM
  • Energy Star® certified
Read Verified Customers Reviews

Takagi T-H3-DV-N is a whole house tankless water heater that can supply your house with up to 10 gallons of hot water per minute. It is powered by natural gas.

Although it is powerful enough for a whole house, we recommend considering other options like Rinnai or Rheem models. Takagi T-H3-DV-N is great, but in our opinion it’s outdated.

One particular difference this tankless unit has is its maximum output temperature. It’s the only residential tankless water heater that can heat the water to up to 185 degrees! Now, I don’t know anybody who likes it that hot. But if for some reason you need to be able to heat it so much, Takagi can do it. Other whole house tankless water heaters max out at 120-140 degrees for security reasons.

Takagi T-H3-DV-N is designed for light commercial use, so its inner parts like the heat exchanger can survive heavy duty usage for a long time. Not that Rinnai or Rheem are worse (they’re not by any measure), but considering how long this model has been manufacturing, it’s very competitive.

Takagi T-H3-DV-N is also almost twice cheaper than our #1 whole house tankless water heater. That’s a big plus to the list of advantages!

We recommend buying a Takagi whole house tankless water heater if you’re looking for a cheap yet reliable and simple unit without any fancy features that can do the job of heating a house with 3 or 4 bathrooms.

Things to Consider Before Buying a Whole House Tankless Water Heater

If you’re new to the world of tankless water heaters, it might be hard to find the right one. Here’s a short guide for you to understand the basics and help you to make an informed decision.

Climate

How much water can a tankless water heater heat per minute totally depends on the temperature of the inlet water. The colder it goes in, the more gas a unit has to burn to heat the water. Which takes more time. Which affects the final flow rate.

That’s why I told in the beginning that the electric tankless water heaters aren’t the best choice for cold climates unless you only need to supply one bathroom with hot water. They can’t cope with really cold water. The flow rate would be far worse than you’d expect.

More on the temperature rise and how it affects the final flow rate you can read in our comprehensive sizing guide.

Hard or soft water

The performance of a whole house tankless water heater does not depend on how hard or soft your water is.

However, it may affect the longevity and the maintenance routine. If your place uses well water or any sort of hard water, you’ll have to do the flushing more often as the calcium buildup will reduce the performance over time.

In order to prevent that from happening you need to do the descaling procedure every now and then (typically once a year). It’s very easy to do but you need to make sure you’re using the right solution. A typical flushing kit would be helpful.

Kelaro Tankless Water Heater Flushing Kit with Rectorseal Calci-Free Descaler
  • Helps maintain the performance and extend the life of your tankless hot water heater.
  • Everything you need in one kit to descale your tankless water heater in 30 minutes or less | Suitable for DIY Homeowner use with easy to follow directions.
  • Includes 1/8 HP Utility Pump, 6 Ft Color Coded Hoses, 3.5 Gallon Bucket with EZ-Off Lid, Instructions & Calci-Free Tankless Water Heater Flush Cleaner - more effective than vinegar with no strong odor.

And if you’re using well water, a water softener system would also help to reduce the damage and extend the life of a tankless unit.

Iron Pro 2 Combination water softener iron filter Fleck 5600SXT digital metered valve 64,000 grain, 64k for whole house
  • Water softener, iron filter, all in one! high flow for whole house use!
  • 64,000 grain capacity, fine mesh resin designed for high iron removal & long life
  • Fleck 5600SXT digital metered valve for efficiency and ease of use, 5 year warranty!
Sale
iSpring ED2000 Whole House Electronic Descaler Water Conditioner, Alternative Water Softener
  • Solves hard water problems without the need for chemicals, salt, or maintenance, while keeping healthy minerals in the water by preventing scale deposits from forming and allowing existing scale to break down
  • Descales your entire water system and prevents scale buildup in pipes. Reduces energy consumption with an average one year payback period. Great for your home and the environment, individuals on salt-restricted diets, and those looking for healthier skin and hair
  • Designed for very hard water areas (10-19 grains). Saves energy and extends the life of your appliances

Sizing

When sizing a whole house tankless water heater you should think about the peak usage. What is the highest possible load that it should be able to handle? Think about the busiest part of the busiest day and calculate how much hot water you would need by adding up all the flow rate of every fixture that’s being used.

Having that said, you shouldn’t buy a bigger tankless unit than you need. If you live in a small house you wouldn’t want to overpay for superpowerful natural gas 199k BTU tankless water heaters.

Electric vs Natural Gas/Propane

We’ve mentioned the main difference in the climate section.

There’s one more significant difference. It’s the price.

Electric tankless water heaters are cheaper to buy but they’re more expensive to operate. They draw a lot of electrical power which is kinda expensive. They often require upgrades to electrical service and take up to 200A. If you don’t have that already, upgrading would cost you a pretty penny.

But they’re more efficient. They also take less space.

Natural gas or propane tankless water heaters are more expensive in the upfront cost, but they could potentially save you a ton of money on energy bill. It’s an on demand system! It doesn’t burn the gas all the time like conventional storage tank water heaters. And gas is usually cheaper than electricity.

What’s more important, they’re way more powerful than electric tankless water heaters. There’s no other choice if you live in a huge house with high hot water demands. And especially if you live in colder climates.

Frequently asked questions

Can a tankless water heater heat the whole house?

Absolutely. Tankless water heaters can easily heat the water for whole house if you size it properly. In our guide we’ve come up with a list of the best whole house tankless water heaters that you can choose from.

How many GPM do I need for a whole house tankless water heater?

It depends on the amount of hot water you would need heated at any given point simultaneously. For a whole house you’d typically want a tankless water heater that can provide at least 5 GPM or more. Some models can handle the demand of up to 11 GPM of hot water.

Are tankless water heaters worth the money?

Absolutely! Tankless water heaters save you money over time by reducing your energy bills. You also get the luxury of instant and endless hot water whenever you need without waiting or worrying that you’ll use all of it.

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