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3 Best Electric Tankless Water Heater (2021): Regular and Inline Hot Water

(Last Updated On: December 1, 2020)

Tankless water heaters that run on electricity are the most affordable option for homeowners looking to retrofit their system. Just as with gas-powered models, electric systems will save lots of money on your energy bills, and give you constant hot water on demand without the limitations of a tank!

Whether you live alone in a studio apartment or in a bustling household with many bathrooms, there are tankless electric water heaters to suit any application! As your tankless plumbing experts, we’ve done the research to help you find your perfect unit! We’ve come up with a list of great models, sorting them into  top sellers, highest overall quality, and the best value models. Keep reading to find the right one for you!

ModelRatingPriceMax. FlowrateSuitable House Size?Suitable Climate?
Stiebel Eltron Tempra 4.5$$$UnlistedLargeCold - Warm
Rheem RTE 134.1$4 GPMSmall - MediumMild - Warm
Ecosmart ECO 27electric tankless water heater3.9$$3 GPMSmall - MediumMild - Warm

Why choose electricity over gas?

    • These units are less expensive to buy, even though gas is often a cheaper fuel
    • They’re a bit more reliable over the long term, because there’s no combustion
    • They don’t need to be ventilated or installed outside the house
    • You don’t have to pay the setup costs of ventilation and gas piping
    • You can get completely off the grid, and use them with solar panels


Best Electric Tankless Water Heaters 2020:

1.  Stiebel Eltron 36 Plus Tempra Tankless Water Heater

Imported from Germany, the Stiebel Eltron Tempra Plus 36 has an innovative design and outstanding build quality. It is an extremely efficient, precise machine, well worth a larger price tag in the long run. This one is a great choice for a larger household (two or three bathrooms) with high demand for hot water.


It’s a very smart design. The Tempra will automatically adjust its internal settings to use the exact amount of power required with minimal wasted energy. In times of high use, it will also adjust the water flow, which helps to ensure hot water even in frigid temperatures. Reviewers were thrilled with its performance. Most say it stays absolutely constant, regardless of how many fixtures or appliances you have running.

Some of the other hot water heaters will have a lag or a drop in output when another source requiring hot water (i.e., faucet, dishwasher) is turned on, which can affect your shower temperature. The Tempra 29 Plus will automatically adjust in real time by slightly lowering the water pressure, preventing uncomfortable temperature fluctuations when you’re trying to get clean.

The Tempra’s unique system is so effective that the manufacturer doesn’t even list a maximum flow rate! That makes this one ideal for high-usage applications where you don’t want to have to think about rationing hot water usage. Of course, depending on inlet water temp and total flow rate, the effective temperature rise decreases with higher flow rates (for information, see this chart). The Tempra does a very good job of compensating, but it’s not a miracle worker.

It has a three-year warranty on parts, which is better than most others on the market. Plus, it has the added bonus of being made in Germany, so you can be assured of superior build quality and reliability over other models. The Tempra has an outstanding reputation for long-term, problem-free performance.


At close to $850, the only big downside to this unit is the price, which is on the higher side for tankless electric heaters. This one is priced close to many gas units, though it is more powerful than gas units that cost roughly the same amount.

Some buyers weren’t as impressed by the automatic management system as others. A couple of reviewers thought it didn’t work as well in the cold as the company claimed, and one reviewer noticed a temperature drop with the dishwasher and the shower on at the same time. However, the vast majority of reviewers said the smart controls more than lived up to their expectations.

Overall: This is the best high end electric tankless water heater out there designed for high-demand residential use. This one is the ideal choice for a five-six person house, with the potential to seamlessly run two showers at once, even two high-flow showers. It’s probably overkill for smaller applications, but if you want the absolute best of the best for your smaller house and can afford the Tempra, we have a hard time finding any reasons why you shouldn’t buy this model.

2. Rheem RTEX 13 Electric Tankless Water Heater



Reviewers say that the stated flow rate might not live up to expectations in especially cold climates, especially in larger households. That’s true of most tankless water heaters, especially models that don’t have smart management systems in the controls. If you live in a very cold area and are planning to use this for more than one low-flow shower at once, this might not be the best choice for you.

In terms of overall functionality, this unit has a relatively low output rate. You will probably have to limit yourself to one shower at a time if you don’t have low-flow fixtures installed in your bathrooms.


This Rheem is a great choice for smaller households (1-2 people) without a tremendous demand for hot water, or for bigger households willing to do one hot water task at a time. This one is not the best choice for the colder northern climates, though, and it’s not for medium/larger households who don’t like to think about managing hot water usage. If you need a compact solution for small-scale use, though, we don’t think you can do any better!

3. Ecosmart ECO 27 Electric Tankless Water Heater

electric tankless water heater

The Ecosmart ECO 27 is Ecosmart’s most powerful heater, designed to handle on demand water heating in even the coldest climates. In warm climates, it can supply most fixtures in your home at the same time. In fact, many buyers used it as their sole water heater for lake houses, cabins, or other vacation properties.  And the price is, comparatively, quite reasonable. It’s a good option for medium-size households with more demand or a colder climate to deal with than the Rheem can handle.


Ecosmart claims the ECO 27 can heat 3 GPM in the coldest of inlet water temperatures (37 degrees), and 6 GPM in warmer climates. That’s a great output rating for the price. This one is a great choice for medium-sized households (3-5 people) looking to save money on their electric bill. It’s also a more consistent performer than the Rheem during the colder months.

It has a similar modulating control system to that of the Stiebel. The Ecosmart also adjusts its power usage and pressure settings to keep a consistent output for you. And, as with the Stiebel, that means increased efficiency and increased energy savings on your bill!

Best of all, it has a lifetime warranty on the unit itself, which is by far the best warranty on the market.


One reviewer cautioned against taking Ecosmart’s performance claims at face value, noting that it did not heat sufficiently at 3 GPM in cold inlet temperatures. Most folks found that the unit performed well in colder areas, but some were less impressed that others. It’s always a good idea to check your inlet temperature before you buy, especially if you live at high altitudes or in far northern regions.

Some reviewers reported hassles in qualifying for the lifetime warranty. There’s some fine print, so you’ll have to be careful to register your unit properly and install it according to the manufacturer’s instructions. Buyers also warned of long customer service wait times when they had issues. This one’s not quite as good over the long term as the Tempra.

This unit probably won’t supply enough GPM for larger households (5+ people) with simultaneous shower needs, unless you’re in a warm climate all year round. For most of us, the Tempra is the better choice for high demand. If you’re in a consistently warm spot, you may be able to save some money by opting for the cheaper Ecosmart.


The ECO 27 is largely well-reviewed; even the people with warranty issues note that their units worked well when they were repaired. The ECO 27 is a great choice for most households, especially for those who need a bit more output or climate compensation than the Rheem can manage. As we’ve said, though, it’s not ideal for larger households which regularly run multiple hot water draws at once.

Buying Guide

Picking the right unit for your household is a matter of weighing your overall needs for hot water (Learn how to size your water heater), the climate you live in, and of course the unit price.

Folks living in warmer climates have a much easier time of it, since less energy is required to get the water to the proper temperature. That means you can take output rates at close to face value, even though we always advise leaving yourself a safety margin between your actual needs and the rated output.

People in warmer climates can therefore get away with buying units with a lower gallons per minute (GPM) output, or at least get to enjoy more reliably high-flow rates that people in colder climates. That’s because a hot water heater that’s installed in a colder spot will have to work harder, which then lowers its overall output capacity.

If you’re in a particularly cold spot, we recommend rounding your supply needs up by at least 30%, closer to 50% if you like to be absolutely assured of having supply. So, if you actually need 4 gallons per minute, you’ll actually want to look for a 5 or 6 GPM to compensate.

Thankfully, many manufacturers make this process easy by providing climate zone charts in their product listings. If you have a look at those, you can get a quick sense of what you can expect from each model in your area.

The other big factor to consider is your household size and the average demand you’ll be placing on your system. Will you need to  have multiple showers running at the same time? Do you want to be able to run, sinks, dishwashers, and washers while your shower is going? Each overlapping demand will require a unit with a higher output capacity.

Add up all your GPM (gallons per minute) usage requirements for a maximum usage scenario that you can use while you’re choosing your new equipment. If you live alone, this probably isn’t a big concern, unless you like to run an appliance while you shower. If you live with one or more other people, you should probably assume that someone else will need at least some hot water at the same time you’re taking a shower.

Think about how conscious of hot water use the people in your house are. It’s also good to ask yourself whether you want to have to think about rationing your usage at all.

If you’re thinking of trying to make a smaller unit work for you, remember that swapping your plumbing fixtures for low-flow models can make a huge difference. If you can reduce the draw from each fixture by even 25%, that will add up quickly as you start to consider multiple draw scenarios.

Be sure to factor in the cost of the installation into your purchase. Each unit has its own installation and conversion demands, and you should be aware of those costs as you work out your budget. Tankless electric water heaters are cheaper and easier to install than their gas equivalents. However, they still probably require professional help unless you are a true DIY talent.

It’s also best to check whether you’re required under the warranty to have an authorized technician perform the installation and other adjustments. Many negative buyer reviews for these units revolve around difficulties in qualifying for the warranty. That’s because those buyers didn’t read the fine print, and invalidated their warranties by performing self-maintenance.

Always read the fine print, and make sure you’re going to be covered for the long term. Remember: it’s better to pay the extra money up front to have a certified installer work on your equipment if it saves you the price of buying a new one when something goes wrong!


All three of these units are a well-made and well-designed. Your success with any of them will depend on picking the right one for your usage requirements.

If you live in an apartment or small house, or  if you are in a household willing to do only one hot water task at a time, the Rheem RTEX 13 is the cheapest and most popular choice. It’s one of the most reliable systems out there, and it’s super space-efficient.

If you are willing to invest in a more seamless experience, the Steibel can handle everything you might throw at it, from cold weather to high demand. Just be prepared to spend more money and set aside more space.

And the ECO 27, for the price, is the perfect middle ground. It’s ideal for medium-sized homes and for smaller installations in colder climates.

To learn more about tankless heaters, read our Best Tankless Water Heater Reviews!

Tankless Reviews was created with the goal of helping people to understand the benefits and practical knowledge related to tankless water heaters. After purchasing my very first tankless heater years back, I realised that other people needed to hear about the incredible money-saving ability of this household item, and wanted to share my lessons with you!