It’s annoying to read countless electric tankless water heater reviews that quote the manufacturer’s literature and still be confused about what is the best electric tankless water heater for your place.
Many of my readers feel the same way when they decide to ask my opinion.
What if I told you I know exactly what you need?
In this article, I’ve covered probably all possible cases when an electric tankless water heater is the right choice and when it’s not. (Please, share your case in the comments section below the article if I haven’t mentioned it).
Want to know the best part?
I’ve shared my knowledge based on all my experience and practice of installing electric tankless water heaters in this article. I also thought it would be useful to hear what the owners say, so I included their reviews too.
Now, let’s not keep the secret till the end. In my opinion, the best electric tankless water heaters are these:
Service Requirements: 113 amps (3 double pole x 40 amp breakers)
99.8 Energy efficient
You were looking for the best electric tankless water heater brand, right?
So here it is, Ecosmart.
In my opinion, Ecosmart deserves to get first place in this rating. More than 1959 happy owners would agree with me.
It’s one of the most popular, reliable, efficient, and technologically advanced electric tankless water heaters brands on the market. These units also have very competitive prices, especially the medium-sized models, like ECO 27.
If you’re completely clueless and you don’t want to do detailed research and be wondering what brand to choose, pick Ecosmart. Read the sizing guide to determine the right size for your hot water demand.
Depending on the model and the groundwater temperature, the flow rate of Ecosmart tankless water heaters ranges from 0.8 GPM (ECO 8) to 8.8 GPM (ECO 36) for the lowest temperature rise.
Here’s a table for Ecosmart ECO 27. The number on the left is the temperature rise (hot water temp minus groundwater temp). The number on the right is the flow rate.
*Results based on outlet temperature of 105 degrees
If you live in warmer climates, Ecosmart ECO 27 will be a better choice for several reasons:
it requires less electric power (120 amps vs. 150 amps in ECO 36) and takes less space in electrical panel (3×40 breakers vs. 4×40 in ECO 36)
it’s able to supply a big house with 2-3 showers working simultaneously (with the temperature rise of 53 degrees)
the price is significantly lower than the ECO 36 and not really much higher than the less powerful model ECO 24 has.
Compared to similar electric tankless water heaters (like Stiebel Eltron), it has a lower activation flow rate (0.25 GPM vs. 0.5-0.7 GPM in Stiebel Eltron 24 or 36).
Why would you care about the activation flow rate?
Because with a higher minimum flow rate, you won’t be able to wash your hands in hot/warm water! If the flow rate is too low, it won’t activate the tankless unit, and water will not be heated, and you’ll have to use cold water.
If you are planning to buy an electric tankless water heater in addition to a bigger one, I suggest you look at Ecosmart ECO 11.
It’s a nice and small electric tankless water heater for single applications, like showers or sinks. In warmer climates, it can handle a shower and two sinks running at the same time!
Ecosmart tankless water heaters show great overall performance. The advanced self-modulating technology adds up to its efficiency and helps you save energy and money, reducing your power bills, as compared to other electric tankless water heaters.
Temp control is super easy. It has a digital screen where you can see and adjust the temperature by 1-degree increments.
Now, let’s review the advantages and disadvantages of Ecosmart ECO 27 electric tankless water heater:
Best performance. At max, it provides 8 GPM
The most powerful unit on the market
Advanced flow control
Very silent compared to others
Patented self-modulating tech
May require an upgrade for your wiring and electrical panel
The warranty terms are a bit too complex for an average consumer
Service Requirements: 54 amps (1 x 60 amp breaker)
99.8 Energy efficient
The second best item in our rating is Rheem RTEX 13 (or RTEX-18 if you need more powerful tankless).
Rheem is a popular water heater brand in the US. They make some of the best natural gas tankless water heaters on the market. But not many people know that their electric models are also very competitive.
Rheem RTEX-13 and RTEX-18 models made their way to the list of the best selling electric tankless water heaters on Amazon. And that’s for a reason.
Many people buy small electric tankless water heaters in addition to their central water heater, and very often, they don’t need big models like Ecosmart 27 or Stiebel Eltron 36. They need a small point of use electric tankless water heater for one or two showers or a shower and a sink, and that’s it.
That’s where Rheem RTEX-13 comes into play.
It’s a small unit that can fit anywhere in your house. It doesn’t require much space.
It also requires much less space in your electrical panel than bigger models. You only need one 60 amps @240V breaker, so even if you have 100A service, that’s enough. And if you’ve got 200A, you can use two of these small electric tankless water heaters.
As for the flow rate, Rheem RTEX-13 can provide up to 3.5 GPM if you live in Florida or Texas. It all depends on the temperature rise, though. Check out our sizing guide for reference.
Rheem RTEX 13 flow rate
Installation is super easy, since electric tankless water doesn’t require piping. If you aren’t sure about your DIY skills, please contact your local electrician.
Although I almost never need help with installation, the Rheem support is very helpful and responsive.
Rheem RTEX-13 and RTEX-18 are VERY efficient. Some of the owners we interviewed report 30% decrease in electricity bill.
The only downside of this unit is that it isn’t certified by Energy Star. It means no “green” rebates from electric utility.
High efficiency: up to 99.8%
Very small sizes
Adjustable thermostatic temp control with a digital screen
Service Requirements: 150 amps (3 DP x 60 amp breaker)
99.8 Energy efficient
German quality at its finest. Stiebel Eltron is a quality brand. And they make great electric tankless water heaters. Their most popular models are the ones for medium and high hot water demand. Although there’s a whole range of sizes, I’m going to review Stiebel Eltron 24 Plus, because it’s the most popular among others.
I don’t know why, but many other electric tankless water heater reviews websites talk about the older discontinued model – a version of Stiebel Eltron 24 Plus.
Here I’m going to review the newer (white) version. It’s not much different in performance but very much more convenient and easier to use.
I’ll be honest. I don’t have experience with this exact model.
But here’s the thing:
I understand how electric tankless heaters work. I know that when a manufacturer talks about 5 GPM flow rate, it means 3 to 4 real GPM because the maximum flow rate is only possible in perfect conditions, which is not the case for 99.99% of owners. And I know that big models require an oversized electrical service.
So, let’s get straight to the technicals and then see what the owners have to say about it.
Stiebel Eltron 24 Plus is designed to replace traditional tank storage water heaters, so they’re pretty powerful even for the whole house usage (if the house is not very big).
It provides up to 5 GPM flow rate. But remember, it’s true only for perfect conditions and small temperature rise. The more common and real number would be anywhere between 3 and 4 gallons of hot water per minute, depending on the temperature rise. Which means you can run two showers and a sink simultaneously without any drops of water pressure.
According to the specifications, Stiebel Eltron requires A TON of energy. As I’ve said earlier, you may need to upgrade your electrical service upgrade, if you don’t have 200A. It may be pretty expensive. For Stiebel Eltron Tempra 24 Plus, you’ll need a place to install two pole 60 amp circuits with a minimum of 6 AWG wire.
Please, make sure to consult your electrician before making a buying decision.
Easy installation once breakers are in place
Stable temperature setting
Super helpful responsive support
Saves space due to its compact sizes
May require service upgrades
High activation flow rate (0.5 GPM for Tempra 24, 0.77 GPM for Tempra 29 and more)
A lot of people who asked me about electric tankless water heaters didn’t want to replace their tank water heaters. They just wanted an additional “booster” to their hot water system to have instant hot water at the sink.
There are two options:
You can install a small tankless electric water heater like Ecosmart ECO 11. It will provide enough hot water for two sinks running at the same time. If it’s installed close to the point of use, there shouldn’t be any problems with delivering hot water. But you might still need to wait for a little before the hot water gets to the fixture.
Another option is to install a mini tank water heater. You get really instant hot water anytime you want. It’s perfect for intermittent use. The downside of this kind of water heaters is that hot water is limited to the tank volume.
When I was preparing this overview, I wanted to include Bosch Tronic 3000 as the best under sink water heater. It’s a tested model. It has excellent reviews on most of the marketplaces, and my clients like it.
But then I decided to do some research. Imagine how surprised I was when I found out that my favorite electric tankless water heater manufacturer also makes mini-tank models!
So let me present to you Ecosmart ECO MINI – the best under sink water heater. It’s manufactured in the United States by a quality and tested brand. It has a sleek design. According to more than a hundred reviews from verified owners, it does its job perfectly.
Now let’s review the technicals.
The sizes are very important for this kind of water heaters, because, you know, people place them under sinks. This one is relatively small. The 2.5 gallons version has 16.2 x 11 x 11 inches. There’s also a 4 and 6 gallons options which are slightly bigger. There’s also a 1 gallon version, but I wouldn’t recommend it for anything. It’s way too small.
Installation is easy and straightforward. Just mount it vertically and plug into a standard 110v outlet. It doesn’t need a dedicated circuit.
Ecosmart Mini 2.5 recovers in 15 minutes. It means that if you use all 2.5 gallons at once, it’ll fill up the tank and reheat the incoming cold water in 15 minutes. If the temperature rise is less than 60 degrees, it’s going to reheat even faster.
REAL Instant hot water
You don’t need to upgrade your electrical service. The unit can run off any standard 15 amp circuit
It’s not “endless” hot water and can’t handle extensive water usage
Service Requirements: 57 amps (1 DP x 60 amp breaker)
99.8 Energy efficient
By the number of mentions of Ecosmart, you may think they’ve sponsored this article. No, they didn’t. The reason why I put their water heaters everywhere is that they DOMINATE the market of electric tankless water heaters.
No, seriously. They win almost every category and only lose to maybe Stiebel Eltron, which is the king for commercial electric tankless water heaters. And there are multiple reasons why people love them so much.
First of all the price. They offer more functionality for the same money.
Let’s review some of the features that make this tankless better.
Ecosmart have their own patented self-modulating technology. It makes the unit uses only the energy it needs to handle the demand.
What does it mean to you? You save money! Some of the owners report a significant decrease in their electric bills.
Compact sizes and sleek design
According to numerous reviews, people use this electric tankless water heater for different purposes. Some want to “boost” their main water heater and have instant hot water at the point of use. Other people install several small units for showers, sinks, washing machines, dishwashers, etc. Almost always the lack of space is the issue.
That’s why it’s important for an electric tankless water heater to have smaller sizes. So it may fit anywhere.
Ecosmart does just that. It can fit under the sink. It can be mounted on the wall in the closet. And it still looks good due to the great design.
Convenient temp control
Ecosmart ECO 11 has a cool digital display that shows you the temperature. You can easily set the temperature in increments of 1 degree.
shows you the temperature. You can easily set the temperature in increments of 1 degree.
Great performance for the price
You can check the current price on Amazon, but I can assure you it’s totally worth it. For the money, you get a decent flow rate somewhere between 1.3 GPM and 3.1 GPM depending on the temperature rise and the climate in your area.
*for residential use when registered properly and installed within 30 days of purchase by a licensed professional
Things to consider when choosing the best electric tankless water heater
As I have mentioned numerous times, electric tankless water heaters draw A LOT of energy. They require a hefty power supply. And your average household typically isn’t always capable of keeping up with a powerful whole house electric tankless water heater.
More often than not they require multiple 240-volt circuits to operate. So if you go electric, make sure your electrical infrastructure can dedicate enough amperage to the unit. Or your tripped breakers will be your constant problem.
Typical tankless draws about 100-120 amps (3 x 40 amp 240v breakers). So to be sure, you should have at least a 200 amp service.
That’s why I always recommend considering gas tankless water heaters first if you think about whole house unit. Yes, they also may require some upgrades with gas lines. But usually, you’re ready to go as is.
Anyway, it’s totally up to you to decide. Natural gas is not always an option. Choose what’s best in your situation.
Flow rate and temperature rise
We’ve already covered the sizing question in our article. But I think it won’t hurt to make a quick reminder.
The flow rate of an electric tankless water heater is how much hot water it can supply at a given temperature rise per minute.
Let’s say, you want to heat water for your shower and a sink. And you live in Colorado. And it’s winter outside.
It means your hot water demand is somewhere between 2.5 to 3.5 GPM.
Now let’s count the temperature rise. We need to subtract the temperature of the incoming cold water from the desired output temperature.
According to our groundwater temperature map, the cold water is around 47-52 degrees Fahrenheit. When we subtract that from the desired 110 degrees hot water, we get 63 degrees temperature rise.
So now we should go and check what model can supply 3.5 GPM of hot water with 60+ degree temperature rise.
Ding ding! We have a winner! It’s Ecosmart ECO 27 (who would have thought, right?).
See, with enough information it’s very easy to properly size an electric tankless water heater.
Activation flow rate
Nobody will tell you this. I’ve never seen anyone talking about this. Yet, it may be a turning point for your decision.
Let me explain.
Although the technology in electric tankless water heaters is pretty advanced, there are limits on how finely they can modulate. And if it tries to heat a very slow trickle of water it would make it dangerously hot. So if the flow rate is too low, the tankless unit won’t heat it at all.
You’ll end up washing your hands in cold water all the time. Or wasting too much water and energy (=money) just to wash your hands.
Bottom line: The lower the minimum activation flow rate, the better.
There’s nothing special and most of the manufacturers provide similar warranty terms. Just make sure you know how it works.
There’s one exception though. It’s the Ecosmart.
They provide a limited lifetime warranty, meaning that if the unit is installed by a professional and you register it in 30 days after the purchase, you’ll get a lifetime warranty. Ecosmart will replace the parts if needed, or even replace the unit itself.
You can save even more money if you apply for a rebate in your local utility. In case you didn’t know, you can get a rebate if you buy a certified energy-efficient unit.