While traditional water heaters remain the best choice for some, tankless models save space and can help reduce your heating bill.
If you’re considering going tankless, your first decision will be to choose between a gas or electric model (you can read up on the merits and drawbacks of both in more detail here). While high-end gas models may be more powerful than electric ones, they are also considerably more expensive and challenging to install. There are also some additional safety concerns to consider. Then there are homeowners who would simply prefer not to use gas. Gas tankless water heaters are typically not as efficient as their electric counterparts, sometimes by a 10 percent margin, so there are plenty of reasons to choose an electric tankless water heater.
Read on for detailed guidance on how to select the best electric tankless water heater for your home.
- BEST OVERALL: Stiebel Eltron Tankless Water Heater – Tempra 36
- RUNNER-UP: EcoSmart ECO 27 Electric Tankless Water Heater, 27 KW
- BEST BANG FOR THE BUCK: Atmor 18kW 3.7 GPM Tankless Electric Water Heater
- BEST FOR SMALL HOMES: EcoSmart ECO 11 Electric Tankless Water Heater, 13KW
- BEST FOR GUEST HOUSE: Titan SCR2 N-120 Electric Tankless Water Heater 220
- MOST VERSATILE: Stiebel Eltron 230628 240V 12 kW DHC-E12 Single/Multi
- BEST POINT OF USE: ECOTOUCH Tankless Water Heater Electric 5.5kw 240V
- ALSO CONSIDER: Rheem RTEX-18 18kW 240V Electric Tankless Water
What to Consider When Choosing the Best Electric Tankless Water Heater
When looking for the best tankless water heater, the process involves more than just determining whether it will heat sufficient water for your needs. The following section looks at a number of key issues that will likely impact your decision as you shop.
There are two main types of electric tankless water heaters: whole house or point of use (often referred to as POU or single point).
When considering replacing a traditional hot water tank with an energy-saving electric tankless model, a whole house solution is the most straightforward and doesn’t require additional plumbing. In new homes, or where guest accommodation has been added, point of use heaters might be the more economical answer. Although initial costs are a little higher, heating water close to where it’s needed means unused water doesn’t go cold sitting in long lengths of pipe, so less energy is wasted. However, there is no one-size-fits-all solution; each installation needs to be assessed individually.
Portability is a challenge because these devices are designed to be permanently wired—even for RV use. If a plug-in electric water heater is required, the best option is probably an electric mini-tank model.
Flow Rate (GPM)
The most important factor in choosing an electric tankless water heater is the amount of hot water the unit can provide. Flow rate is given in gallons per minute (GPM). A shower or washing machine, for example, needs about 2 GPM.
In theory, adding together a home’s total number of showers, tubs, washing machines, and so on would indicate the size of the water heater necessary. However, as these almost never run all at the same time, the result is an overestimation. Instead, certain assumptions are made: In general, a 1- or 2-bath home needs around 5 GPM. A large 3- or 4-bath home would need a 10 GPM unit.
GPM is impacted by the temperature of the supply water, so the same model fitted in the Southern U.S. would provide a higher GPM than fitted in Northern states. Additionally, with electric tankless water heaters, in particular, GPM is often secondary to power (given in kilowatts—kW). This figure gives both the energy used and the heat provided.
All this can be very confusing to potential buyers. Fortunately, manufacturers generally provide excellent guidance about the suitability of their heaters for different levels of hot water consumption. They also frequently provide the range of temperatures achievable. If further advice is required, it’s a good idea to consult a qualified plumber or heating professional.
One of the main benefits of tankless water heaters is efficiency. They only heat water when you need it, so very little energy is wasted, resulting in lower utility bills. Electric tankless water heaters are typically more efficient than their gas counterparts, the challenge is finding accurate ratings.
Gas models usually quote a Uniform Energy Factor (UEF) rating, a standard established by the U.S. Department of Energy. Unfortunately, manufacturers of electric models seldom follow suit. Some use the Energy Factor rating that preceded UEF, but this is no longer considered sufficiently accurate. There is no suggestion that these are misleading, but given that each manufacturer might use different criteria for testing, this is not the most accurate way of making comparisons.
That said, a percentage efficiency is usually quoted instead. The efficiency of gas models ranges from 80 percent to a high of 93 percent, electric models are often 98 or 99 percent efficient. That’s good for the environment and for lowering household bills.
Physical size is seldom a challenge with electric tankless water heaters. Water pipes and electrical conduits are small in diameter, so units are generally very compact and surprisingly slender. That said, dimensions might be important when installing point-of-use models.
Most are extremely quiet and don’t have the firing noise associated with gas models. Some claim to be completely silent.
These devices typically have some form of digital display. However, the controls and information provided vary considerably. Basic models might just have up and down arrows to increase or reduce power and a readout of the actual temperature. Others can have preset temperatures held in memory, provide adjustable flow control to reduce power consumption, or monitor and report energy savings.
Installation and Maintenance
Electric tankless water heaters are considerably easier to install than gas models because no venting is required. The devices are more compact and with no need for large air gaps around them, they can be positioned just about anywhere that electricity and water can be provided. However, while small and point-of-use models often run from a 120 volt supply, larger and more powerful models require 240 volts and usually two or three breakers. DIYers with a thorough understanding of household electrical systems will be able to tackle the relevant work themselves; no specialty tools are required. Otherwise, the services of a professional should be sought.
While these devices are largely trouble-free, a small amount of annual maintenance will keep them operating at peak performance and extend their working life. Manufacturers usually provide comprehensive instructions, but in essence, there are two tasks to carry out.
- Most models have a screen filter to stop particles of dirt from entering the heater. This should be checked for obstruction and cleaned if necessary.
- The system needs to be flushed to prevent the buildup of chemical deposits that reduce efficiency and could eventually prevent the unit from working. This is particularly important in hard water areas. In essence, water and power need to be disconnected and a small pump is used to flush white vinegar through the heater to clean it. Commercial flushing kits are available for this purpose.
Our Top Picks
The following picks come from a variety of leading manufacturers and have been divided into different categories to make it simple to find the best electric tankless water heater for a particular situation.
The impressive Stiebel Eltron Tempra is one of the most powerful electric tankless water heaters on the market, capable of providing a maximum of 7.5 GPM, which should be sufficient to provide enough water for four showers running simultaneously. It can heat water to 140 degrees Fahrenheit, well above the U.S. Department of Energy’s (DOE) maximum recommendation for household water temperature of 110 degrees Fahrenheit.
It’s also highly efficient. Given that no system is ever 100 percent perfect, a rating of 99 percent efficiency makes the Stiebel Eltron among the best you can buy. Auto-modulation minimizes fluctuations in water temperature and it runs virtually silently. Preferred temperature can be preset into memory.
This 36 kW model requires a 240V supply and three 50 amp breakers. There are six Stiebel Eltron models in the Tempra range, offering high-quality solutions for installations of all kinds. Safety is recognized by independent UL and CSA certification.
The EcoSmart is a compact unit that still offers competitive performance with a maximum of 6.5 GPM. It also has a minimal activation requirement of 0.3 GPM, so you don’t have to turn faucets on full power in order to get hot water. Less responsive units would waste water and electricity used for heating, but this one provides optimal control.
Like many other leading devices, it uses flow modulation. This ensures optimum energy conservation while ensuring that changes in supply temperature or pressure have no impact on hot water output. The maximum achievable temperature is 140 degrees Fahrenheit and its energy efficiency is 99.8 percent.
Running at 27 kW, the EcoSmart ECO27 requires a 240V supply and three 40A breakers. The device is both UL and CSA certified for safety.
The budget-friendly 18 kW Atmor has a theoretical maximum of 4.2 GPM but a practical output of 3 GPM in the majority of cases. While a drop in supply temperature can reduce that figure significantly, the Atmor has been designed to work with particularly low input temperatures. It can supply almost 2 GPM for incoming water that’s just 37 degrees Fahrenheit, something many high-end competitors struggle to achieve.
Despite the low cost, there’s still a digital thermostat adjustable in single-degree increments, and self-modulated control. The use of stainless steel for internal components helps maximize durability.
The Atmor range offers electric tankless water heaters from 3.5 kW right up to 36 kW, providing money-saving solutions for just about every hot water demand. This 18 kW unit requires 240V and three 30A breakers.
Those who live in compact modern homes will want to take a close look at the EcoSmart ECO 11. Rated for a maximum of 3.1 GPM, this affordable unit can provide constant hot water for a shower and low-flow faucet simultaneously. It is one of few electric tankless water heaters that uses the accurate UEF standard, with outstanding efficiency of 99.8 percent.
As with all the models in the EcoSmart range, the ECO 11 has self-modulating technology. The DOE estimates it saves around 50 percent on hot water costs per year. Digital temperature control allows adjustment in 1-degree steps, anywhere from 80 degrees to 140 degrees Fahrenheit. The EcoSmart ECO 11 is a 13 kW device requiring 220V and a single 60A breaker.
Electric tankless water heaters are ideal for extra bathrooms or guest houses when extending an existing tank system would be costly or impractical. The compact Titan is an excellent choice for these situations. It’s competitively priced and can produce up to 4 GPM of output. It has an efficiency rating of 99.5 percent.
Installation is easy, and control is via simple up-and-down arrows so there’s nothing complicated for guests to understand. However, it does require a minimum input temperature of 65 degrees Fahrenheit, making it less than ideal for cold regions. The 11.8 kW Titan needs a 220V supply and a single 60A breaker.
With a maximum flow rate of around 2 GPM, the Stiebel Eltron DHC-E12 can be used for single or multipoint installations. While often fitted for sink use, it’s equally capable of providing hot water for a low-flow shower. It’s a great choice for remodels and equally good for permanent fitting in boats and RVs. With its renowned reliability and durability (capable of surviving seismic activity), it’s also popular in commercial environments such as offices, warehouses, and gas station restrooms.
The Stiebel Eltron DHC-E12 has an efficiency rating of 99 percent. It uses microprocessors for advanced flow control, ensuring constant temperature anywhere from 86 degrees to 140 degrees Fahrenheit. It requires a 240V supply and uses a single 50A breaker.
Most electric tankless water heaters are relatively compact, space-saving units, but at just 11 by 7.5 by 2.35 inches, the Ecotouch ECO55 really can go just about anywhere. Despite the diminutive dimensions, you get up to 1.5 GPM and an efficiency rating of 98 percent. It can provide constant hot water at up to 116 degrees Fahrenheit.
It’s also tough enough for commercial uses with a fire-retardant case and tempered glass front panel. It is self-modulating for temperature stability and has protection circuits for overvoltage, overheating, and leakage. The unit can be fitted at any angle, so it will function perfectly well on a boat in motion, for example.
The Ecotouch ECO55 requires a 240V supply and uses a single 30A breaker.
Rheem has tremendous experience with both gas and electric tankless water heaters. The high-quality RTEX-18 is rated for up to 4.4 GPM and offers advanced self-modulation, helping it achieve an efficiency rating of 99.8 percent. It can raise water temperature for one or two showers well beyond the recommended 110 degrees Fahrenheit level, making it an impressive yet economical choice for modest homes.
It is widely recognized as being easy to install. Operation is simple, with a clear display and large dial offering control in single-degree increments.
Brass-topped heating elements offer high durability and are easy to replace should the need arise. This Rheem model is an 18kW unit requiring a 240V supply and two 40A breakers.
FAQs About Electric Tankless Water Heaters
Having read through the information on important considerations and reviewing the top picks, you are no doubt in a better position to decide which is the best electric tankless water heater for your needs. However, some questions may remain. The following provides answers to many that crop up regularly.
Q. How does a tankless water heater work?
As soon as you turn on a faucet or shower, a flow sensor activates an electric heating element. As soon as the water is turned off, so is the heat. It’s generally called “on-demand” water heating. No energy is wasted in filling a tank with water you don’t need, which is more economical and eco-friendly.
Q. Do electric tankless water heaters need to be vented?
No. Unlike similar gas models, there is no carbon monoxide byproduct. Generally speaking, that makes electric tankless water heaters considerably easier to install.
Q. Can you still shower if your water heater is leaking?
Yes, you can still shower. But to prevent water damage, the leak needs professional attention as soon as possible. A water heater with a standard tank has the potential for a catastrophic leak. Whereas an electric tankless water heater does not hold water in a tank, but malfunctioning parts can still cause small leaks which may result in water damage.
Q. What are the signs your hot water heater is going out?
Dirty water, particularly if there are rust particles, is a sure sign of internal damage. Inconsistent performance and lack of response to temperature input are other indicators.
Q. How do you flush an electric tankless water heater?
The process usually involves turning off water and electrical supply, removing the heater element, filling the internal chambers with white vinegar, and then flushing. Manufacturers usually provide instructions specific to each model.
Q. How long do electric tankless water heaters last?
According to the U.S. Department of Energy, a useful life of 20 years or more can be expected.