- 1 Top 7 Best Tankless Water Heaters Compared
- 1.1 #1 EcoSmart ECO 11 Tankless Water Heater
- 1.2 #2 Stiebel Eltron Tempra 24 Plus Tankless Water Heater
- 1.3 #3 Bosch Electric Mini Tank Water Heater
- 1.4 #4 Thermoflow UT15 Tankless Water Heater
- 1.5 #5 Rinnai V Series V Tankless Water Heater
- 1.6 #6 Takagi TH-3 DV-N Condensing Natural Gas Tankless Water Heater
- 1.7 #7 Gasland Outdoor Tankless Water Heater
- 1.8 How We Decided
- 2 Best Tankless Water Heater Buying Guide
If you’re looking for the best tankless water heaters, check out our list of the top tankless gas and electric water heaters as well as mini tank water heaters on the market. We’ve spent hours looking at the specs and consulting consumer reviews to bring you this list of the most efficient tankless water heaters worth the money. In order to find the top water heaters we evaluated for safety performance, energy efficiency, water conservation and ease of installation.
Our top pick, the Eco smart ECO 11 electric tankless water heater, features a self-modulating design and is able to cut your water heater bill by up to 60% over a traditional water heater.
Top 7 Best Tankless Water Heaters Compared
#1 EcoSmart ECO 11 Tankless Water Heater
Award: Top Pick
WHY WE LIKE IT: 240 volt, 13 KW electric water heater boasts high energy efficiency thanks to digital temperature control and self modulation, giving you continuous, on-demand hot water. It’s big enough to be a whole home water heater in warm climates and a point of use water heater for a shower and sink in colder climates.
This highly efficient electric tankless water heater is versatile enough to be used as a point of use in line water heater for a bathroom or kitchen fixture in very cold climates or it can function as a whole home water heater in hot climates, delivering enough hot water for two showers or two sinks and one shower at once in areas where the groundwater is around 60 degrees F.
The EcoSmart electric tankless water heater also saves up to fifty percent on the energy cost of heating your water. Its on demand electric heat exchanger is more thermally efficient–approaching 99% efficiency–than any natural gas tank water heater, and since it only heats up when you’re using hot water, there’s no energy wasted heating up water you’re not going to use. As with all electric water heaters, it also eliminates NOx emissions and cuts down on the greenhouse gas footprint of your home. Your heating and cooling are very important to your home.
#2 Stiebel Eltron Tempra 24 Plus Tankless Water Heater
Award: Honorable Mention
WHY WE LIKE IT: A compact whole house tankless water heater that provides enough hot water flow for two showers at once in most continental US climates, making it a great choice for large families.
One of the best electric tankless water heaters on the market by consumer ratings, the Stiebel Eltron Tempra 24 Plus is distinguished by its relatively high output of 18 kw, nearly fifty percent more than the Eco Smart (our top pick.) The Stiebel Eltron electric tankless hot water heater also uses advanced flow rate control, which is a feature that ensures uniform water temperature when running showers or sinks by limiting flow rates rather than flowing cold water. There’s nothing worse than sudden temperature rises or drops when taking a shower.
While installation of this tankless electric water heater does require some knowledge of running electric and water lines, it’s possible to do in an afternoon for an experienced DIY-er. That said, make sure you have at least 2x 50 Amp breakers to handle the current flow. You may also want to check out our best patio heater guide for more options.
#3 Bosch Electric Mini Tank Water Heater
Award: Best Mini Tank Water Heater
WHY WE LIKE IT: A convenient and energy saving point-of-use mini water heater that fits under the sink and gets up to 98 percent thermal efficiency.
Although tankless heaters are becoming more and more popular, this mini tank water heater from Bosch lets you conveniently install an electric water heater at the point of use for up to two sinks or one shower. It fits easily under sink cabinets or can be floor or wall mounted. Unlike the tankless water heaters from Siebel Eltron and EcoSmart, it uses a regular 120V electric supply and doesn’t require 60 or 100 Amp breakers. However, the hot water runs out when the water in the tank is used up, so it can’t provide hot water constantly.
Compared to tankless units and other electric models and water heaters this Bosch unit saves water, since you don’t have to run the water while it heats up and so there’s no waiting. It may also save you electricity and reduce energy bills since it only heats up incoming water you’re actually using and not heating up water you don’t use. If you’re looking for indoor/outdoor heating, check out this list to find the best large space heater.
#4 Thermoflow UT15 Tankless Water Heater
Award: Best Mini Tank Water Heater for Kitchen Sinks
WHY WE LIKE IT: A 4-gallon mini tank with energy efficient thermostat and water saving fast heating recovery rate, making it great for kitchen sinks or as a mini water heater for dual bathroom sinks.
Much more convenient to install than electric tankless water heaters that require a 240V power supply, this under sink mini tank electric water heater is a plug-in unit that runs on 120V and only requires 2x 15 Amp breakers, rather than the 60-100 amps necessary for the Stiebel (our #2 pick.) The Thermoflow saves water by only heating up water in the tank when needed, and it can also be mounted in-line with a main water heater tank in order to act as a buffer and supply continuous hot water while the larger tank is refilling. This is useful for cold climates and in households with large families.
The Thermoflow is larger in capacity than the Bosch electric mini tank, but offers less maximum water pressure range, 115 psi vs 150 psi. But, as a point-of-use electric water heater, the Thermoflow is an efficient, fast and durable choice. You can also outfit your home with the best space heater for large room.
#5 Rinnai V Series V Tankless Water Heater
Award: Best Gas Tankless Water Heater
WHY WE LIKE IT: A high efficiency tankless gas water heater supplying 7.5 gallons per minute of hot water and employing energy and water saving features such as on demand heating and smart app control.
Our top choice among gas tankless water heaters, the Rinnai 7.5 GPM is up to 40 percent more efficient than traditional natural gas water heaters, and has the added benefit of supplying continuous hot water with no intermittent cold water flow, up to a rate of 7.5 gallons per minute. This is more continuous water heating than you get with either the EcoSmart or the Stiebel, our top two picks overall.
Compared to all-electric tankless water heaters, this natural gas water heater is more complex to install, typically requiring professional installation, and takes up significantly more space. However, it still takes up less space than a normal water heater with a water tank. Your home may also need the best heaters. The best wifi smart air conditioner can help in the summer.
#6 Takagi TH-3 DV-N Condensing Natural Gas Tankless Water Heater
Award: Best Tankless for Large Families
WHY WE LIKE IT: The Takagi TH-3 remains energy and water conserving while delivering a solid 10 gallons per minute of hot water, making it a great choice for higher demand households that still want to save energy over a tank water heater.
This Takagi tankless water heaters meets energy star qualifications and the SCAQMD standards for ultra low emissions gas appliances. Comparable to Rheem and Rinai tankless natural gas water heaters, it provides up to 10 GPM, the highest flow rate of any gas or electric tankless water heater on our list. This is billed as being enough for three bathrooms/ kitchen sinks in warm climates or two in colder climates. It heats water more quickly on demand than the EcoSmart or Bosch electric water heaters, and takes up less space than conventional gas or propane water heaters.
It’s more costly than the electric tankless water heaters or the Rinnai tankless water heater (our #5 pick) though it does provide more hot water flow– 10 GPM vs 7.5. Overall, the Takagi TH-3 is a solid choice for a tankless water heater for the whole house. For your basement, the best sump pump will keep everything, including your water heater, safe.
#7 Gasland Outdoor Tankless Water Heater
Award: Best Budget
WHY WE LIKE IT: An outdoor and portable water heater that includes anti freezing protection. It’s an efficient propane tankless water heater that’s light and compact enough for RVs and travel/ camping uses, too.
This propane gas tankless water heater, designed for outdoor use, is small and light enough to take with you on camping trips or to be employed as a water heater for an RV. It uses advanced technology like auto gas shut off in case of flame out and an anti overheat shut off feature, as well as an anti-freezing drain plug, to ensure safe year round operation.
Compared to a natural gas or electric tankless water heater, this propane water heater has somewhat of a different purpose in mind. While it’s not suitable for replacing your home water heater or installing indoors as a point-of-use tankless water heater for bathroom sinks or showers, it is portable and lets you enjoy hot water on demand even while roughing it camping or on an RV trip, and it saves water and energy compared to similarly sized units, boasting up to 11.5% fuel savings over similar output propane water heaters. The best tools for your home can often help you to save.
How We Decided
In order to select the best tankless water heaters, gas heaters and mini tank water heaters on the market, we looked at a number of factors common to all home water heaters and a few specific to the different types of tankless water heaters.
For all of the water heaters on our list, we only included those with key safety features like overheat shut off and, for gas tankless water heaters, leak detection with auto-shut off. After all, safety is one of the big reasons people go for tankless water heaters over full sized storage tank water heaters.
For electric tankless water heaters, we only included models that achieved 98 percent or greater thermal heating efficiency, as well as performance of at least 1.5 GPM hot water flow at common winter groundwater temperatures of between 37 and 42 degrees F.
Finally, for propane tankless water heaters, we limited our choices to those with built-in overheat protection, gas shutoff in case of flameout and at least 1.5 GPM of hot water.
Best Tankless Water Heater Buying Guide
The Most Important Features
- Auto Shut Off
Electric tankless water heaters are inherently safer than traditional pilot light gas powered storage tank water heaters, in that there’s no large heated water tank to spill and no carbon monoxide emissions. That said, an automatic shut off in case of blowing the breakers is an important safety feature that preserves the the water heater itself as well as avoiding electrical fires. For natural gas tankless water heaters, auto shut off is even more important, since it helps prevent gas leaks and fires in case of an overheat condition.
- Temperature Modulation vs Flow Limiting
When the limits of their heating capacity are reached, some tankless water heaters flow cold water until the volume enough for them to heat the water again, while some limit outflow pressure so you get constant temperature water, just less of it as the maxiumum heating capacity is reached. Which is better for you depends largely on your preference and whether you’re looking at a tankless water heater for showers and baths, kitchen sinks or bathroom sinks.
- Gas vs Electric
While electric tankless water heaters like the Stiebel Eltron (our #2 pick) or the EcoSmart (our top pick) are more energy efficient and eliminate some carbon emissions as well as the potential for carbon monoxide and NOx emissions, the feasibility of installing an electric whole house water heater depends on the climate as well as the type of electrical connections you have available. Many homes only have the required 240 volts and 60 Amp breakers in laundry rooms. Gas tankless water heaters are still safer than traditional storage tank water heaters, while having very limited electricity demands.
Tankless Water Heaters FAQs
What are some of the advantages of tankless water heaters?
Compared to tank water heaters, tankless water heaters are safer, take up less interior space and can save money on utilities, as well as upgrading the ecofriendliness of your home. For example, the Stiebel Eltron electric tankless water heater (our #2 pick) delivers hot water at up to 4 gallons per minute with 18 KW of heating energy, yet because it only heats the water on demand, uses far less energy overall than a storage tank water heater of similar output capacity. In addition, even gas tankless water heaters are more efficient and safer than tank water heaters, since they use forced venting for exhaust, don’t store hot water and don’t rely on an exposed pilot light.
How difficult is tankless water heater installation?
Depending on the model and your level of DIY skill and interest, installing a tankless water heater can be a project of a few hours on a weekend or a task better left to professionals. In general, provided you're comfortable with water lines and basic electrical work, an electric tankless water heater can be a DIY job saving you possibly expensive installation costs, while gas water heaters are somewhat more involved to put in.
What do manufacturers mean by a lifetime warranty?
A lifetime warranty is usually a warranty against defects in materials and workmanship that has no time limit to make a claim. "Lifetime guarantees" can be a tricky concept either referring to the lifetime of the customer, the product, or the manufacturer. More often than not, household appliances, in general, do not come with lifetime warranties. Washing machines, for instance, come with manufacturer warranties that last one or two years.
What does GPM stand for?
GPM stands for gallons per minute and refers to the amount of water tankless heaters can process per minute. When it comes to heating water, a tankless unit capable of processing 4 gallons of water (4 GPM) will comfortably run a couple of quick showers, suitable for a household with two or three occupants but won't be able to heat water constantly. For a continuous supply of hot water, a tankless unit with 6GPM, such as the EcoSmart ECO 27, is recommended. The ECO 27 is ideal for families with up to 5 members living in a two-bathroom house. Another solution for endless hot water is that Rheem RTGH-95DVLN – a High Efficiency 9.5 GPM Indoor Natural Gas Tankless Water Heater. This tankless heater has a stainless steel condensing heat exchanger, a built-in condensate neutralizer, and 1/2" Gas line compatibility up to 24ft.
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