If you’re looking to replace your existing, enormous water heater tank, tankless water heaters are your best bet. They are energy efficient, space saving, and overall a great choice to upgrade your home in the energy efficiency style of the future.
We’ve chosen the Stiebel Eltron Tempra 29 Plus Electric Tankless Whole House Water Heater, 240 V, 28.8 kW as our best electric water heater and the the Takagi T-H3-DV-N Condensing High-Efficiency Natural Gas Indoor Tankless Water Heater for our best choice in gas.
Both of these will deliver endless hot water and energy savings, which translates to happier family members and a happier wallet.
Keep reading for advice on choosing your own tankless water heater and a list of the best 24 water heaters, both gas and electric, that we could find.
How to Choose a Tankless Water Heater
Hot running water has different flow rates depending on what task you’re doing. The kitchen sink requires less flow than the shower, for example. Simultaneous household tasks place a further strain on water flow.
For example, if you have a larger family or roommates, and you plan to have the dishwasher running while someone is washing clothes, you may want to increase your flow rate expectation.
Water flow is measured in gallons per minute or GPM. If you want to take a shower during a dishwashing cycle, you’ll need to know what the flow rate is of both simultaneously. The shower GPM is 1.5, while the dishwasher is 1. So your tank should have a 2.5 GPM capacity.
The other part of this is temperature. Water coming from the grid is typically a certain temperature. Your water heater needs to make up that difference inside the flow rate.
The other choice you have to make is whether gas or electric.
If you choose an electric tankless, the location or locations you choose must have the correct voltage outlet.
You also have to decide if your house’s electrical system can support the demands of going tankless. Although tankless water heaters use less standby energy overall, and are more efficient than a tank, they do have differing energy requirements. You need to check this system.
The third consideration is that it must be on its own circuit. It’s too dangerous to loop it with another appliance or outlet.
If you decide to invest in a gas heater, check to see if the gas supply line will support it. If the old gas line isn’t sufficient, you’ll need to upgrade that as well (and add that cost in to your system estimate.)
Also, a gas tankless water heater must be ventilated, and if you are putting it into a space that previously held a tank water heater, you might have to retrofit the space for adequate ventilation.
Gas or Electric: Which is Right for Me?
Choosing the fuel type will depend on your situation and your personal preference. There are a few different considerations to make.
Electric models cost around $500 to $700 while a gas model will start around $1000. Both types of tanks are rated to last around 20 years with proper maintenance.
Electric is about 98% efficient while gas is around 85%. Both present real improvements in efficiency over a tank water heater, however.
Gas is certainly cheaper to operate on paper, but the higher efficiency of the electric models may offset this cost. Adding in installation costs and maintenance costs, a homeowner can expect to spend about 15% more in lifetime operation costs.
Both types of tanks will need research for proper installation. Electric models require a certain electrical capacity, their own circuit, and proper voltage outlets.
Gas models will need the right capacity gas line and ventilation systems. Older model houses rarely have all the pieces for either types of heater, so some work will be required for most installations.
Electric water heaters require very little maintenance. Occasional cleaning of the inlet filter should do it.
Gas will require yearly inspection from a professional.
Top 24 Tankless Water Heaters
1. Rinnai RUC98iN Ultra Series Natural Gas Tankless Water Heater, Concentric/Twin Pipe Installation
The first heater is a gas heater with a twin pipe installation. Rianni offers a condensing technology that is more efficient than the standard gas tankless heater. It offers a 98-140 degree heating range. The ignition meets both California and Texas NOx emissions standards.
The required width for installation is 18.5” x 26” x 10”, and the weight is just under 62 pounds. Both gas and water connections are 3/4”
The company offers a 5 year warranty for parts and a 1 year warranty for labor. It must be mounted on an exterior wall with outside ventilation.
Some customers may notice a tiny drop in water pressure, but it isn’t as noticeable with low flow shower heads. Otherwise, the capacity for multiple water tasks is handled quite well.
Its operation is quiet, and supplies plenty of hot water at just the right temperature.
2. Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
The Ecosmart ECO is an electric heater with self modulating technology. It allows you to control temperature in single degree increments, which is good for your savings.
It’s a 240 volt machine, and needs 150 dedicated AMPS.
It can handle up to 6 gallons per minute for homes in warmer climates. Although it’s a smaller space footprint, it can provide water for larger capacity tasks such as jacuzzi tubs.
Homes in colder climates can still enjoy 3.5 gallons per minute. This should be plenty for multiple water tasks without sacrificing heat or pressure.
Makes sure you have the correct amount of breakers in your home to handle running the system. Otherwise, filling a large tub, for example, might flip the breaker switch.
One drawback to this size system is that it doesn’t begin to heat the water until you have a certain amount of water flow triggered. For much smaller homes, this might affect your hot water supply. Make sure to calculate how much water you want to use before installing the system.
3. Takagi T-H3-DV-N Condensing High Efficiency Natural Gas Indoor Tankless Water Heater, 10-Gallon Per Minute
The Takagi is a gas heater with computerized features so you never have to worry about the pilot light.
It has an EnergyStar certification and fulfills the NOx emissions requirements.
It offers a temperature range of 100 to 180 degrees Celsius, which should be plenty for normal household water usage.
It has an excellent GPM at 10, which is enough for homes where multiple water usage tasks will happen simultaneously. In northern climates it can handle heating for 3 baths. For southern climates, four.
It’s extremely quiet despite its large capacity and you shouldn’t have any problem with either the flow or the amount of heat you need for your water.
If you install it yourself, make sure to bring the manual with you when purchasing your materials. Otherwise, professional installation shouldn’t take too long.
The one drawback of installation is that the anchors are 15 inches apart instead of 16, so it might cause trouble if you are expecting to mount it to regular studs.
4. Rheem RTE 13 Electric Tankless Water Heater, 4 GPM
Rheem offers a smaller electric machine that produces 4 gallons per minute. It has a standard half inch water connection requirement and a brass/copper heat exchange.
It’s great for point of use water heating, meaning you can have almost instant hot water in your kitchen sink, for example. It’s compact, making it a great fit for smaller spaces, or for use with other water heating units.
It requires 240 volts, and 13 kilowatts. Its space footprint is roughly 9 x 10 x 5 inches (yes, really) and is enough for smaller water usage.
Setting it to a lower heat setting and using low flow shower and faucet heads further increases its efficiency. It’s a lower priced option with a slightly easier installation.
If you don’t need a huge capacity machine, this would be a good direction to take.
5. Bosch T 2.7-Gallon Electric Mini-Tank Under Sink Water Heater
If you need a small point of use machine to complement your water heating system, Bosch offers an electric mini tank.
You can plug it into a 120 volt outlet for independent usage or you can connect it inline with a larger hot water source.
You can mount it on a shelf, on a floor, or on the wall. This allows you more control over the placement and more freedom to decide how to supplement your hot water.
The glass lined tank offers extra protection and durability, and the whole unit blends seamlessly with existing appliances and decor. The dimensions are 13.75″ H x 13.75″ L x 10.75″ D and it weighs just 15.5 pounds.
6. Stiebel Eltron Tempra 20 Plus Electric Tankless Whole House Water Heater, 240 V, 19.2 kW
Steibel’s electric heater is a digital control system that requires no ventilation. It has a single flow sensor design, and upgraded electronics.
It requires 240 volts and 19.2 amps. It is recommended to double check your breaker capacity before purchasing to make sure that your system can be installed properly.
One advantage is that the automatic sensor adjusts the flow of the water to avoid temperature fluctuations. The water flow is consistent enough to run multiple water usage tasks without sacrificing any pressure.
It is energy efficient, and has a smaller space footprint considering the capacity. It would be great for condos or smaller houses that have a lot of activity, but are smaller square footage.
One drawback is that you might want to go ahead and get a professional to install this, just to make sure that your circuitry is sound and you have the right connections installed without headache.
7. Eccotemp FVI-12-LP High Capacity Propane Tankless Water Heater
Eccotemp’s propane tankless water heater is a high capacity machine with fully independent gas and water controls. You can make adjustments digitally.
This model is great for smaller homes, and uses only 2 watts and 1.07 amps during operation. It comes with a horizontal ventilation system so it can be installed straight out of the box.
It has a 3.6 GPM capacity, and can offer a 45 degree rise in temperature at that rate. It offers a 77 degree rise at 2.3 gallons per minute.
The 110 volt power cord supplies the external exhaust fan and the digital thermostat and temperature display. It only uses gas when the hot water is on and running.
The dimensions are on the smaller side as well at 15″ x 4″ x 24”h, and 33 pounds. The electronic ignition is water pressure triggered, making it great when energy conservation is critical.
8. EcoSmart 8 KW Electric Tankless Water Heater, 8 KW at 240 Volts with Patented Self Modulating Technology
For smaller residences in mild climates, this unit is perfect. It still offers EcoSmart’s one degree increment temperature adjustments. It provides 1.5 GPM, great for low flow shower heads and faucets.
For homes in colder climates, or with higher GPM requirements, it’s also great as a point of use unit, to supplement your existing water heating system.
It’s on the small side at 12 x 9.5 x 4 inches, and will save a ton of space in homes where space is premium. It also weighs just 4.8 pounds.
It requires a minimum of 100 amp electrical panel to install with 1 40 amp double pole breaker. Plumbing connections are half inch.
Although simple to install, self installation might void your warranty. Check with the manufacturer to be clear on this issue.
9. Rinnai RL94iN Natural Gas Tankless Water Heater, 9.4 Gallons Per Minute
The Rinnai is a gas heater that offers temperatures of 98 to 140 degrees Fahrenheit residentially.
With this model you can have hot water in up to 5 appliance and plumbing outlets simultaneously without affecting temperature.
It has a 9.4 gallon per minute capacity, though it still offers 40% energy savings over the standard tank water heater and significant space saving.
It mounts directly to the outside and uses a concentric ventilation system. It measures 9.3 x 14 x 23 inches and weighs 50 pounds.
It provides enough hot water that there’s no need to adjust the temperature while in use. It’s relatively quiet, about the same amount of noise as a running refrigerator. It only requires about 0.26 gpm to trigger the heating function.
Although it’s possible to install this yourself, due to the gas line requirements and vent system, you might consider a professional for peace of mind.
10. Marey ECO 110 Electric Tankless Water Heater
This is another smaller option for tankless heaters. The hot water output is 3 gallons per minute and attaches easily to the existing water supply.
This heater requires 240 volts and 50 amperage. It is extremely tiny at only 3 x 8.6 x 14.8 inches and weighing 7.5 pounds. If space is precious, then this unit will fit right in.
It is simple to install by yourself in a weekend. It is definitely on the smaller side so make sure to do the calculations so you know how much water you need for your small space.
11. Westinghouse WGRTNG199 199K BTU Natural Gas High-Efficiency Tankless Water Heater with 0.98 Energy Factor
This Westinghouse heater has a massive capacity 11 gallon per minute offering at a 35 degree temperature rise. It is energy star certified.
It offers multiple safety functions if gas makes you nervous. There’s a state of the art gas leak detector and a dual stage antifreezing mechanism.
You an adjust water temperature by 1 degree increments to give you total control, and the flow sensor and flow control maintain constant temperature during use.
It’s larger and will require more work during installation. It measures 27.6 x 17.3 x 27.6 inches and weighs 80 pounds. You’ll need to securely install it on an exterior wall. Gas lines will need to be 3/4 of an inch.
This unit will require regular inspection by a professional, but that’s worth it for the high capacity heating capability, especially if your hot water needs are larger.
12. Takagi T-K4-OS-NG Tankless Water Heater, Natural Gas, Outdoor
This Takagi model is built specifically for outdoor installations, which means it won’t require extra venting to the outside. It has built in freeze protection and doesn’t require any special ventilation caps.
If you must have it indoors, it can be arranged with a few parts sold separately (plus proper exterior ventilation.)
Water pressure is an impressive 8 gallons per minute. The dimensions are 8.5 x 13.8 x 20.3 inches
It includes controls to maintain temperature and to prevent freezing. It monitors the incoming water temperature to maintain efficiency.
13. Atmor AT-D18TP-AZ ThermoPro 18 kW/240V 3.7 GPM Digital Thermostatic Tankless Electric Instant Water Heater
If you are struggling to find a tankless water heater suitable for a particularly cold water grid, this system is set up for you. It can heat incoming water with temperatures as low as 37 degrees Fahrenheit at 1.9 gallons per minute.
It requires 240 volts and 18 Kw. It’s recommended that a professional install this system so that all required criteria are met.
That being said, the machine is easy to use thanks to a digital temperature control system. You set your desired temperature, and the heater uses only the amount of energy required to actually heat the water once triggered.
If you live in a warmer climate, the unit is especially efficient and delivers a higher gpm rate than the above 1.9 gpm. It’s important to do all calculations necessary so you can make sure this is suitable for your needs.
14. Rinnai V65EP 6.6 GPM Outdoor Low NOx Tankless Propane Water Heater
Our second Rinnai on the list is a propane tankless water heater that complies with NOx emissions levels. It delivers up to 6.6 gallons per minute for a home with one to two and a half bathrooms.
It’s a compact system that still delivers good water pressure for larger requirements. It measures 9 x 14 x 23 inches and weighs under 50 pounds. It’s also the only unit on this list certified for installation in mobile homes.
This unit is easy to install at least part of the way and requires 120 volts. It produces hot water in about 15 seconds at the nearest outlet, and just under a minute in some further away.
One good thing about the digital controls is that they hold the last setting even after a power outage. Other models tend to default back to factory settings so this is some convenience over the others. It does well holding temperature steady during usage.
15. Takagi T-T-KJr2-OS-LP Outdoor Tankless Water Heater, Propane
Another entry by Takagi, and this one’s just as qualified. This is an outdoor installation only unit, but it delivers 6.6 gallons per minute of water. It has internal freeze protection for homes in colder climates.
This unit is designed for smaller spaces such as apartments and condos. It measures 6.7 x 13.8 x 20.3 inches, and weighs 38 pounds.
One downside to this model is that equipment needed to install the unit safely outside will cost a little bit extra. Installing it yourself will void any warranty you have with the company.
The pipe requirements are 3/4 inch, and if you live in a colder climate, pay close attention to the size of your propane tank. The unit can only heat as well as your propane supply.
The manual is particularly helpful, and should allow you to trouble shoot any minor error codes yourself.
16. Rheem RTG-84XLP 8.4 GPM Low NOx Outdoor Tankless Propane Water Heater
Another Rheem entry, this time an impressive 8.4 gallon per minute heater at a 35 degree rise. Increasing the rise by ten degrees only lessons the gpm to 6.6.
This unit is a little larger, measuring at 14 x 10 x 26 inches and 54 pounds. It has an electric ignition, so there is no pilot light to worry about.
It produces a little more noise as well, and so mounting on some kind of insulation might be required, though check with an installation professional before doing this.
It needs a 3/4 inch supply line, and it needs a fair amount of pressure to actually heat the water. This shouldn’t be a problem for a household that needs this size unit however. Most likely things will be running with enough pressure to heat.
It will need to be installed outdoors only, preferably by a professional.
17. Bosch WH27 Tronic Whole House Electric Tankless Water Heater, 240 Volts
This whole house electric tankless water heater can heat up to 3.3 gallons per minute with a 55 degree temperature rise. This is impressive for homes situated in colder climates.
It provides endless hot water for one major application at a time with a 97% efficiency rating. It has a built in flow sensor to deliver consistent temperatures during each task.
You’ll probably need an electrician to install it since it’s unlikely that your house already has the proper electrical configuration.
The best part of this tankless heater is endless hot water while using a markedly reduced amount of energy. You’ll never get to a cold shower, even if you are the last person in the house to use it.
It has a small footprint, and will save a ton of space over traditional tank heaters, at 15.5 x 4.5 x 12.5 inches and weighing 19.6 pounds.
18. Noritz NRC661-DV-NG Indoor Condensing Direct Tankless Hot Water Heater 6.6 Gpm-Natural Gas
Noritz is a natural gas indoor tankless water heater that delivers 6.6 gallons per minute of water flow. You’ll be able to perform several simultaneous tasks at once, especially if shower heads and faucets are low flow.
It will need proper exterior ventilation, but this is a high efficiency condensing model. These produce a cool exhaust instead of hot, which will give you more options when choosing a ventilation system.
You should probably have a professional install this, though it’s possible to do it yourself. It vents with PVC and works well overall. It’s efficient, and condensation is low. Overall a good choice for larger hot water needs.
19. Rheem RTG-64XLN 6.4 GPM Low NOx Outdoor Tankless Natural Gas Water heater
Rheem’s midsize machine is an electric heater that offers 6.6 gallons per minute with a 35 degree rise. It’s an outdoor installation natural gas heater.
You’ll need to have a 3/4 inch gas line, but ventilation isn’t necessary since this is an outdoor installation. It comes with a remote so that you can adjust the temperature settings without having to go outside or handle the unit.
It easily keeps water heated to the desired temperature and is 85% efficient. It’s perfect for small to midsize water heating needs, and spaces.
Overall, its performance is similar to a tank heater in that it keeps the temperature consistent, and there’s no threat of cold water when turning off and on the water flow. Midsize family homes will do nicely with this unit.
Make sure that you do not enclose the unit completely in your outdoor installation as the exhaust from the unit will cause the pilot light to go out.
20. Ecosmart ECO 24 24 KW at 240-Volt Electric Tankless Water Heater with Patented Self Modulating Technology
This Ecosmart unit is 98% efficient and configured for climates where water temperatures are as low as 37 degrees. It can heat nearly 3 gallons per minute at this temperature.
For homes in southern climates where water temperatures stay much higher, this model can supply higher demand water jobs such as jacuzzi tubs.
Digital controls allow you to adjust the temperature in one degree increments so you can set a temperature that is exactly right for your home’s needs.
It requires 240 volts and is self modulating. It’s on the smaller side at 17 x 17 x 3.8 inches and weighs just 11 pounds.
You’ll need to make sure that your home has the required amperage to supply the tank, and that the set up is done with the correct materials. Not surprisingly, installing it yourself voids the warranty, though the cost of the unit is probably less than the cost of installation. That would be your choice.
21. Rheem RTGH-95DVLN 9.5 GPM Indoor Direct Vent Tankless Natural Gas Water Heater
This Rheem model is a 94% efficiency natural gas water heater that can be installed indoors. It’s a condensing heat exchange that produces cold exhaust.
It has intelligent design controls, so that it can self regulate and produce maximum efficiency. Digital display shows both temperature and any error codes to make fixing problems easier.
It includes a digital remote control to adjust temperature without having to touch the unit directly. If you choose to install outdoors, it has freeze protection up to minus 30 degrees Fahrenheit.
Because this is a standard condensing type unit, it exhausts to the exterior through a standard pvc pipe.
It provides 9.5 gallons per minute, plenty for a large household using multiple water appliance tasks at once. You’ll need to purchase the exhaust supplies separately, and since this is natural gas, it should probably be installed by a professional.
22. EcoSmart ECO 27 Electric Tankless Water Heater, 27 KW at 240 Volts, 112.5 Amps with Patented Self Modulating Technology
This is EcoSmart’s most powerful tankless heater. It’s great in colder climates, producing 3 gallons per minute at 37 degree water intakes. In warmer weather, it’s capable of up to 6 gallons per minute.
It’s relatively affordable for a unit at this capacity and is highly efficient. It self modulates to provide maximum energy efficiency. The warranty is associated with the unit itself, so it will transfer should you sell your residence.
Overall, this is a great affordable mid-size option, though you may have to handle slightly lower output in colder weather. If you’re in a southern or warmer climate, it won’t make any difference at all.
Be sure to read the lifetime warranty carefully, and consult with a professional when deciding on how to install.
23. BOSCH Tronic 3000 9.5 kW (US9) Electric Tankless Water Heater
This Bosch model is a wonderful point of use electric unit, putting out nearly 10 gallons per minute. It can be installed on any wall in any direction.
It’s 98% efficient with minimal standby loss. It operates on 220 at 85% capacity, giving you a few options with your electrical grid.
This unit is perfect for low water needs, or to supplement an existing hot water system. It is compact and can be installed anywhere you need to boost hot water usage.
It needs to have a dedicated breaker, but otherwise it is easy to install and use quickly. One drawback is that it requires 0.75 gpm to trigger the heating unit which is not a problem in the kitchen, but might cause issues in a smaller bathroom sink.
There are two temperature settings to give you some control over your usage and energy savings.
24. Stiebel Eltron Tempra 29 Plus Electric Tankless Whole House Water Heater, 240 V, 28.8 kW
The Stiebel is a higher end electric tankless water heater that can handle demand for a larger household. It uses a self modulating design that automatically adjusts internal settings to use the exact right amount of power.
It also automatically adjusts water flow to help keep temperatures hot even when the temperature drops. The manufacturer doesn’t even list ideal gallons per minute because it’s so efficient for higher usage households.
Although it might be overkill for smaller households, the price is well worth the investment for larger homes where water usage is higher.
The Winner – Gas
Overall, our choice for a gas household tankless water heater is the Takagi T-H3-DV-N Condensing High-Efficiency Natural Gas Indoor Tankless Water Heater. Although it’s priced a little higher than others on the list, and is natural gas, it delivers consistent water flow to multiple destinations simultaneously.
It has safety features, so if you are nervous about using natural gas, this should give you some peace of mind. This new design doesn’t use a pilot light so you won’t have to worry about keeping an eye on that.
The digital display shows you all the current settings, which can be accessed through the front panel. It can be installed indoors with little trouble.
The Winner – Electric
Stiebel Eltron Tempra 29 Plus Electric Tankless Whole House Water Heater, 240 V, 28.8 kW is our pick for best electric unit. Although smaller households may not need all the power it has, if you can afford this unit, it will be well worth it regardless.
With this, you’ll never notice a difference between it and the traditional tank water heater, except to see a drop in your electric bills, and the ability to get into your utility closet again.
It’s a great overall unit, and well worth the investment. Even if your household is small now, this unit gives your family room to grow and expand without having to sacrifice hot water.
Questions? Drop us a comment below, and be sure to share this with anyone else looking to go tankless!