The 5 Best Electric Tankless Water Heaters for Endless Hot Water

Are electric tankless water heaters worth it?

I hear that question all the time by people looking to replace their inefficient tank water heater. Or, maybe they are trying to go with a green home that is more sustainable and less wasteful of energy.

Whatever the reason to be looking into a tankless electric water heater, the answer is yes to a lot of people. The only thing to keep in mind is that it is not a one size fits all type of scenario. What will work great for some may not be the case with others.

We’ll dive deep into all the pros and cons of electric tankless hot water heaters in this article in a bit. Let me give you a few brief reasons to love inline electric water heaters.

Imagine never running out of hot water.

That’s right. An electric tankless hot water heater can provide endless hot water on demand.

They will save you money. And they will last for over 10 years. In some cases more like twenty!

Ok. I have your attention.

Which is the best electric tankless water heater, you ask?

I’ve compiled a list of the top five best electric on demand water heater reviews to help guide you through the process of choosing the one that is right for your needs.

You can see how they stack up head to head in this comparison table below if you don’t have time to read the whole article. Otherwise, keep reading for more details.

Stiebel Eltron 36 Plus Tempra

Flow Rate:
8 GPM

Min. Flow Trigger:
0.77 GPM

Electrical Requirements:
Amperage draw: 3 x 50 A 3 x 44 A

Features:
Automodulation

Price:
$$$½

Check out on Amazon.com

Bosch Tronic 3000 T ES8

Flow Rate:
7 GPM

Min. Flow Trigger:
0.5 GPM

Electrical Requirements:
Amp 12A/Volts 120

Features:
Thermal efficiency is 98%

Price:
$$½

Check out on Amazon.com

Ecosmart ECO 27

Flow Rate:
6.6 GPM

Min. Flow Trigger:
0.3 GPM

Electrical Requirements:
113 A amperage draw

Features:
Self-modulating heat sensor

Price:
$$$½

Check out on Amazon.com

Rheem RTEX-13 240V

Flow Rate:
4 GPM

Min. Flow Trigger:
0.3 GPM

Electrical Requirements:
60A breaker

Features:
Simple installation

Price:
$$$

Check out on Amazon.com

Marey ECO150 220V/240V

Flow Rate:
3.5 GPM

Min. Flow Trigger:
0.5 GPM

Electrical Requirements:
70A breaker

Features:
Resists hard water

Price:
$$

Check out on Amazon.com

Best Electric Whole House Tankless Water Heater for Cold Climates

Stiebel Eltron 36 Plus Tempra Review

Pros

• 8 GPM for 30°F Temperature Rise
• No Venting Needed
• Takes Up Very Little Space
• Advanced Flow Control for High Water Demand
• Auto Modulation Saves up to 30% Energy Costs

Cons

• Expensive installation should only be done by a professional

There are not many large electric tankless water heaters for whole house use that can actually handle the job.

The Stiebel Eltron Tempra 36 Plus is one of the very few that is up to the task.

Let’s take a close look at the features to see why I rate this the best whole home tankless electric water heater.

Flow Rate

With an 8.0 GPM water flow rate from a 30° temperature rise, there are few electric tankless hot water heaters that can match that.

That means that you can set your temperature for 105° when your groundwater is 75° and run two showers, a sink, and a dishwasher at the same time and never run out of hot water.

Admittedly, there are only a few places that get that high a temperature for groundwater, so another scenario is a 60° groundwater temperature for a 50° temperature rise that gives you 5 GPM.

With low flow shower heads, you can still get two showers running with a dishwasher and still have enough gallons per minute to enjoy hot water.

Advanced Flow Control

When you are pushing the limits of the gallons per minute with high water demand but still expect endless hot water, this feature will slow down the flow rate.

It will drop the water pressure slightly, but doing this will make sure that the water has time to heat up and nobody has to deal with a lukewarm shower.

Self Modulation

Not to be confused with the Advanced Water Flow Control, this feature will automatically detect the temperature of the incoming water and use the appropriate amount of energy to heat it to the proper setting.

This will keep it running much more cheaply than other electric whole house tankless water heaters.

Constant Temperature Output

When a shower is running, for example, and then somebody opens a tap in the kitchen, this feature will keep the temperature from dipping while the other tap comes up to temperature.

Whatever the temperature is set to, this will always be the temperature of the water.

Energy Savings

When compared to other electric tankless water heaters, it is much more efficient and saves money on your electric bill.

With very smart internal circuitry, it won’t break the bank when it comes to electricity usage.

To stay in control of your bill the Stiebel Eltron Tempra 36 Plus inline electric water heater also offers an energy monitor which allows you to control your energy savings.

99% Energy Efficient rating is top of its class.

Verdict

Made in Germany with the kind of engineering you would expect from Germans, this Stiebel Eltron Tempra 36 Plus is the top rated tankless electric water heaters for the whole house.

If you live in a warm area, your energy costs will be lower, you will enjoy a steady stream of endless hot water and will take up very little space.

For the price, it just makes sense to go with Stiebel when your water demands are high.

Best Point of Use Electric Tankless Water Heater

Bosch Tronic 3000 US12 1.8 GPM Review

Pros

• 1.8 Gallons Per Minute Flow Rate
• Can be installed under a sink or in a closet for Point of Use applications
• 98% thermal efficiency rated
• Advanced Flow Control for High Water Demand
• 145°F maximum temperature

Cons

• Hard wired so must be professionally installed

There is basically an electric on demand water heater for every need. Small point of use water heaters like this Bosch Tronic 3000 US12 really ticks a lot of boxes for people looking for a small hot water heater.

Here are some of the features that you will love about this compact electric tankless water heater.

Flow Rate

With a 1.8 GPM flow rate, it will give you enough hot water for a point of use unit for a shower and bathroom that it can fit right under a sink.

With that flow rate, you can run a shower and a faucet at the same time if they are low flow water saver fixtures.

Highly Efficient

With a thermal efficiency rating of 98%, the Bosch Tronic 3000 US12 can get the water to the point of use without losing any heat and using very little energy to get it there. CFC-free foam insulation keeps the water in the pipes from cooling down.

Typical users of this unit see reductions in their electricity bills in the range of 10 to 30% when switching from a tank water heater.

Space Savings

At just 5 pounds and 6.5″ x 12.25″ x 3″, it can fit right under the sink in a kitchen or bathroom. It can be mounted on a floor, shelf, or bracketed to a wall. With no need for venting, there is hardly any place that this electric tankless water heater won’t work

Long Lasting

A glass lined inner tank is resistant to corrosion and calcification in hard water settings. This extends the life of the Bosch Tronic 3000 US12 by a long shot.

With a 5 year warranty on the heat exchanger, it should last you longer than your large, inefficient tank water heater by at least a few years.

Best Uses

There are a few good ways to get the most out of the Bosch Tronic 3000 US12.

If you have an RV or tiny home, then this is a great way to get as much hot water as you could ever hope for without impacting your living space.

Living off the grid and going with only solar or wind generated power can still give you endless hot water with a small electric tankless water heater. It is highly efficient as I noted and requires no gas line.

If you need water in a bathroom that is far from a source like another electric on demand water heater or even tank system, then you can set this up to work in conjunction and enjoy hot water as soon as you turn on the faucet.

If you have a larger house with higher water demands, then buy several and install them where needed. This is a great way to save a lot of money on your energy bills by not having a running tank heater all day when nobody is using it.

Verdict

The only downside to this point of use hot water heater is that it needs to be hard wired and should be done by a qualified technician. The installation is very straightforward in most cases and shouldn’t cost too much. 

In my opinion, this is the best point of use water heater on the market and comes with the trusted Bosch name.

Most Efficient Tankless Electric Water Heater

Ecosmart ECO 27 Review

Pros

• 6.6 GPM water flow rate with 30°F temperature rise
• Digital temperature control in 1° increments
• 90% smaller than similar units
• Copper and stainless steel components for efficiency and longevity
• Saves up to 50% on energy costs

Cons

• Installation can be expensive due to the cost of the wires and breakers needed

For most medium sized homes, you don’t need to think too hard about the best electric on demand water heater. The Ecosmart Eco 27 is simply the top rated endless hot water heater on the market.

Not only does it come at a great price, but the Ecosmart Eco 27 also saves money as the operating costs are so low.

Here are a few reasons I think the Ecosmart Eco 27 is the best tankless electric water heater for medium size homes.

Flow Rate

With a water flow rate of 6.6 gallons per minute with a 30°F temperature rise, which in a warm climate means you can have 4 low flow showers running at once.

Now, most medium size single family homes don’t have four showers running at the same time. So if you have two showers and, say, a dishwasher you will have endless hot water with no issues.

Energy Efficient

A self-modulating heat sensor will help keep the inline electric water heater running at just the right energy level. For instance, if there is high water demand, generally other tankless water heaters will just have the water not be as hot since it can’t keep up. Ecosmart Eco 27 will adjust the water flow so you get the right temperature every time.

In addition to that, it will adjust how much energy it uses based on the water demand.

Space Saver

At 17″ x 17″ x3.75″, it is so small that it is hard to imagine that you can get up to 6.6 GPM out of something that can fit inside a backpack.

It is 90% smaller than other inline electric water heaters that offer up the same GPM and use the same amount of electricity.

Easy to Maintain

By using copper and stainless steel in the heater exchange and the hardware, it is easy to find replacement parts in the event any of them give out.

If you buy a service valve kit, sold separately, then you can easily flush the system if you live in a hard water area.  

Installation

3/4″ NPT male water connectors make it easy to hook up to the water supply, especially when using flex hoses.

Where installation falls flat is from the circuits and wires needed. It can get expensive with #8 wires, and 240V requiring 3 x 40 breakers. In some cases the breakers will need to be upgraded which adds to the expense.  

It needs to be hard wired by somebody that knows what they are doing, that is for sure. If you, or somebody else, does know how these things work, then the installation is pretty straightforward.

Verdict

For those with a medium sized, single family house, then this is the best electric tankless water heater. It gets the job done and saves money.

There is a lot to love with this endless hot water heater. So much so that if you have a bigger house with high demand for water, then I would recommend putting two of these in so you can run multiple points at the same time. It also helps to have each one close to the point of use, too.

In my mind, it is the best tankless electric water heater for most whole home uses.

Easiest Installation Tankless Electric Water Heater

Rheem RTEX-13 240V Review

Pros

• Super easy to install without a professional
• Gets 4 GPM flow rate
• Takes up a small amount of space
• Great for studio apartments or guest bathrooms
• Max temperature of 140°F

Cons

• Flow rate slows down when water demand is high

When you really just want to plug it in and let it do its thing, there is the Rheem RTEX-13. Great for use as a Point of Use tankless water heater, it can be mounted anywhere you like and provide endless hot water on demand.

Let’s take a closer look at the features that makes this the best electric tankless water heater for easy installation.

Flow Rate

4 GPM might not seem like a lot in the grand scheme of things, but depending on your needs, it is very generous considering the size and price.

If you mount this under a bathroom sink, for example, you can run a faucet and a shower at the same time.

As long as you use low flow fixtures. Which everybody should be doing to conserve water.

The one thing to consider is that this is meant for warm groundwater areas. The 4 GPM comes when there is a less than 30° temperature rise, so it does drop down to about an average of 2.5 GPM. Again, this is sufficient to run two fixtures at the same time as long as they are low flow.

Installation

If your house is equipped with a 240 V system and 60 Amp breakers then this can easily be installed with just a little know how. If you do feel more comfortable having a professional or if you need to change your breaker box, then an electrician can do the job in less than a couple of hours.

It can be floor mounted or bracketed to a wall and the 3 foot electric cable and 1/2 NPT adapters come included to save you a trip to the hardware store.

Space Saver

At only 12.63″ x 8.25″ x 3.63″, it’s roughly the size of a hardcover book. Put it under a sink, in a bathroom closet or a cupboard. You can now store way more stuff where your old tank system was. And it’s easier to get to when you want to adjust the temperature or if you need to fix it.

Energy Efficient

99.8% energy efficient means that there is almost nothing wasted. The water is heated evenly and gets to the tap without dropping temperature.

The amount of your electric bills will be the only thing dropping!

The ability to set the temperature in 1°F increments also helps stay efficient as you don’t aren’t forced to set the temperature higher than you want.

You can expect to save up to 30% off of your current electricity bill by making the switch to the Rheem RTEX-13 240V inline water heater.

Verdict

This is an excellent on demand hot water heater that is efficient, small and economical. It will last quite a few years with a 5 year warranty to back it up. It should pay for itself within the first year of use.

That said, it is not for every household.

High water demand houses or ones that are in colder Northern climate, then you should consider a bigger whole house on demand water heater.

Or, consider adding a unit to each point of use in the house. If you have three of these, then even bigger households will see endless hot water.

Best Cheap Electric Tankless Water Heater

Marey ECO150 220V/240V-14.6kW Review

Pros

• Very cheap price
• Up to 3.5 GPM with 30°F temperature rise
• Resists hard water and corrosion
• 0.5 GPM low flow trigger
• Easy to read LCD screen
• Very easy installation

Cons

• Very low GPM in colder climates

Sometimes you get more than you pay for.

This is certainly the case with the Marey ECO150 endless hot water heater. For less than other brands with the same specifications, you get a no nonsense, easy to install and operate inline water heater.

Let’s take a look at the features.

Flow Rate

A 3.5 gallon per minute water flow rate is pretty good not only for the size of the heater, but especially for the price.

With low flow fixtures, you can get use of a shower and a dishwasher or faucet. Or even two showers as long as there aren’t other fixtures running at the same time.

Minimum flow rate to trigger the heater is 0.5 GPM so your low flow fixtures should be at least that GPM to get hot water.

Space Saver

A little bit bigger than the size of a book, it can fit under a sink, or anywhere else you want it to be that is close to the point of use.

It is so small, and so economical that you can easily buy multiple units to have in other areas of the house.

Energy Efficient

Expect savings of up to 30% on your electricity bill. Consider the low price, this endless hot water heater pays for itself within the first year.

Smart technology allows you to accurately set the temperature. Getting exactly the right temperature you’re looking for adds up to savings since you don’t have to set this higher than you actually want.

Verdict

This is a pretty straightforward affair. If you want to save money and still get decent gallon per minute water flow rate, then don’t look any further.

A 5 year warranty will give you peace of mind that you made a good purchase.

What Size Electric Tankless Water Heater Do I Need?

Sizing an endless hot water heater is not difficult at all to do. You just need to do a quick evaluation of your water usage and demand.

How to size a tankless water heater is important for two reasons.

One, you don’t want to overspend and end up with an inline water heater that is way more than what your hot water usage demands.

Two, you definitely don’t want one that doesn’t give you the Gallons Per Minute of hot water flow rate that you need based on your water usage. If this is the case, you’ll end up taking endless lukewarm showers.

Let’s get started.

Step One

Tally up the GPM of all the fixtures in your house.

If you have recently upgraded to low flow fixtures then you probably already know what the GPM rate is. Or, if you have the manuals handy, they will give you the average.

If you don’t have that then a cheat sheet of what most fixtures use is right below.

Step Two

On a typical day, observe what fixtures are being used and when. Take note of the ones that get used simultaneously.

Once you get a sense of which fixtures are used at the same time you can make your calculation.

If you typically find a shower and dishwasher get used at the same time then you know your GPM will be around 3 GPM if they are low flow. If not then the higher end will be around 4 GPM or so.

Whichever your appliances, do this calculation and you have your required gallons per minute for a tankless electric water heater.

Step Three

Find out your groundwater temperature.

You can do this by using a thermometer and running it under the cold faucet.

Or, you can consult this groundwater temperature map below. Note that these are average temperatures. You can also contact the USGS office for your state and ask them what the groundwater temperatures generally are for more up to date information.

Once you know the incoming water temperature, you can calculate the temperature rise.

Step Four

Decide what temperature you would like your hot water to come to. Most electric tankless water heaters have a default maximum of 120°F, but can be adjusted to 140°.

Since the higher the temperature, the lower the GPM you can get from it, a lower temperature is best.

Most people will do fine with a 110°F temperature setting.

Now, subtract your incoming water temperature from the hot water setting and you have your temperature rise.

65°F is a typical temperature for some Southern states, so let’s use that for this example. Subtracting that from 110°F puts us at a 35° temperature rise.

Step Five

Check this temperature rise against the chart for your particular model and you will have the GPM.

That number will determine how many fixtures you can run at the same time and still expect hot water to arrive at your desired temperature.

Check out this article on how to size a tankless water heater with a temperature rise calculator for more details.

Wrapping it up

The best electric tankless water heater is the one that fits your needs best. That’s why I didn’t single any one of these over another since they all serve different purposes.

They are great for ease of use, cost effectiveness and easy installation. If you live in the South or have a small household with low water demands then I definitely think this is the way to go.