Choosing The Best Electric Tankless Water Heater – Complete Guide

For decades, conventional water heaters have been found in the overwhelming majority of American houses. You have probably seen them: they have that classic tank for storing hot water. On the other hand, Tankless systems have grown in popularity over the last twenty years, owing largely to their lower installation costs.

Water heating makes for 18% of your home’s total energy use. Installing a tankless water heater in your house is a sensible, cost-effective, and energy-efficient method to keep your water warm—and your wallet full. According to, tankless water heaters can be up to 34% more effective than incandescent storage-tank water heaters in houses that consume 41 gallons or less of hot water each day.

According to the EPA’s Energy Star program, putting a tankless water heater in the home can save a family around $100 per year (or more!). If those numbers resonate with you, it may be time to consider a tankless water heater for your home.

Do not be alarmed! These are just a few questions our tankless water heater buyers guide will help you address. Our tankless water heater guide will help you get the information you need to select the appropriate equipment for your house, and it extends beyond the type and model to buy. You might even know more than the salesman at the end!

Tankless Water Heater: Description

We have all used ordinary tank water heaters, which do the job but are not particularly efficient. No matter how well insulated it is, the hot water within the tank will eventually lose its heat – it is just how the world works.

The only way to keep that water hot is to warm it up – a never-ending loop that wastes energy and money. In most cases, standby heat loss amounts to 10-20% of total yearly water heating expenditures. The energy used to heat water in some households with typical tank heaters is much larger than the energy used to heat the house!

Tankless water heaters were created to overcome the drawbacks of traditional water heaters by offering a more energy-efficient solution to maintain a constant supply of hot water. They can quickly heat water at the point of use rather than storing (and constantly reheating) it because they use robust gas burners or electrical elements. It makes sense to heat water only when required, and avoiding standby heat loss usually means lower energy expenses.

Tankless heaters are more efficient in consuming fuel and minimizing standby heat loss (gas or electrical energy). By regulating their fuel consumption, these machines only consume as much energy as is required to heat water at the actual flow rate.

When you open a sink tap that draws 1 GPM, you use less fuel to heat the water than if you open a tub spout that draws 5 GPM. As a result, relative to a tank heater, it’s not uncommon to observe fuel-use energy savings of up to 50%.

How Does a Tankless Water Heater Work?

  1. It all burns off the hot-water faucet.
  2. When water enters the heater, a flow sensor detects it and signals the control panel to begin producing hot water.
  3. The control panel in a gas-fired unit activates the fan, which sucks in outside air, releases the gas valve, allows gas to enter, and ignites the burner.
  4. The heat exchanger absorbs heat from the burners and transmits it to water flowing through the tubing of the exchanger.
  5. The mixing valve tempers the superheated water leaving the converter.
  6. The panel will modify the gas valve, mixing valve, and flow-regulating water valve if the temperature sensor detects that the water surpasses or falls short of the required setting.
  7. Exhaust gases are carried away, and combustion air is conveyed to the burner through a sealed vent (or pair of vents) through a ceiling or outside wall.

Tankless vs. Tank-Style Water Heaters

Tankless water heaters work in a completely different way than traditional water heaters.

Conventional tank-style water heaters retain hot water in a tank and require electricity to keep it hot until it is needed.

When a tankless water heater is used, it only heats water when it is needed.

Let us take a closer look at each:

Tankless Water Heaters Tank-Style Water Heaters
On-demand water heating. Water is heated and stored in a tank for future use.
Installation sometimes necessitates a significant upfront cost and/or modifications. Both the buying price and the installation cost are low.
Energy-efficient. Even when there is no need for hot water, energy is consumed.
The design is compact, and it is mounted on the wall. It will take up a considerable amount of room.
It is crucial to pick the proper size. The normal storage capacity spans from 20 to 80 gallons.
If properly maintained, the service life can be as long as 20 years. The average service life is 8 to 12 years.

Factors to Consider When Purchasing a Tankless Water Heater

Flow Rates (Gallons per Minute—GPM)

You will need to make a checklist of all the hot water gadgets you intend to use at any one time if you want to heat your entire house. For example, do you think you will want to use the shower and the dishwasher simultaneously? Two showers at the same time? Add the total flow rates of those devices once you have estimated your home’s average use (gallons per minute).

This data is readily available; simply contact the device’s maker if you have any queries. If you want to minimize the flow rates of your devices, you may install low-flow water fittings, which can help you save money on electricity if you intend to use many devices simultaneously.


There are a few crucial aspects to consider when selecting a tankless water heater. The temperature to flow rate ratio is one of the most critical considerations. To put it another way, tankless water heaters are rated on a scale that considers the highest temperature rise (how hot your water can reach) at a certain flow rate (the number of gallons of water being heated per minute). It may appear to be difficult math, but do not be put off – it is far simpler than it appears.

Temperature Rise

Subtract the temperature of the incoming groundwater (pre-tank) from the desired temperature of your water to arrive at this value (set temperature). In most dwellings, the typical entering temperature is roughly 50ºF (10ºC). Of course, this will vary depending on where you reside and when you will be boiling your water.

You will want to think about these things (for example, if you live in a warm area all year or a region exposed to particularly cold winters). Your post-tank heated water should be around 120ºF (49ºC) for most of your household gadgets.

Keep in mind that the higher the incoming water temperature and the lower your set temperature, the more hot water flow your tankless water heater will generate, and vice versa. The more energy it takes for your groundwater to rise to the ideal water temperature, the more power it takes.

It is vital to remember that flow rates and temperature rise will change every device, and you will need to account for the various ratios. Here are typical flow rates (GPM) and average target temperatures for several common household devices:


Tub 4.0 GPM 102ºF
Shower 2.5-3.0 GPM 104ºF
Washing Machine 2.0 GPM 120ºF
Dishwasher 1.5 GPM 110ºF
Kitchen Sink 1.5 GPM 110ºF


Note: (If your dishwasher does not have its own internal heater, you will want to heat the water to 140ºF)


Condensing tankless water heaters are energy efficient because they harvest and absorb heat from the unit’s exhaust. The residual exhaust heat can assist in hot water production, and because the exhaust gases are cooler, less expensive venting materials can be used.


Any cold water remaining in the hot-water line is looped back to the tankless water heater with a recirculation system. A pump pushes water through a designated return pipe to the heater in these setups. Recirculation provides hot water nearly instantaneously, avoiding the waste of pouring cold water down the drain while waiting for it to heat up.


Prices range from under $170 for modest gas-fired devices to over $2,000 for high-output heaters that can feed two showers at once; $1,000 is approximately normal.

Electric tankless heaters cost between $90 and $900. The cost of a first-time installation is more than the cost of a simple tank renewal.

Types of Tankless Water Heaters


If you plan to utilize many devices simultaneously, whole-house tankless heaters are the best option. Smaller types, such as the Takagi TKJr2OSNG (6.6 GPM), can adequately heat a typical one- or two-bathroom condominium or small family home. Larger varieties, such as the Rinnai RL94eN (9.4 GPM), can simultaneously heat up to five plumbing and appliance units without running out of hot water.


Unlike whole-house water heaters, point-of-use water heaters focus on a single appliance or device, giving consistent hot water to only one faucet. These heaters are typically used to heat domestic faucets such as the shower, kitchen sink, or dishwasher and should be positioned as close to the target equipment as possible.

Since point-of-use heaters are linked to the incoming water supply, there is virtually no lag time for your water to heat up. Considering that the average residential water heater is 80 feet away from the appliance’s heat, this makes a considerable impact. That’s a significant increase in the distance that hot water must travel before reaching your faucet.

Other Factors to Consider

Deciding between a whole-house tankless heater and a point-of-use tankless heater might be difficult. While it depends on several elements crucial to your family—cost, economy, home size, and preferred temperatures—there are a few key considerations.

Type of Home

Is your home a brand-new construction or an older structure? This is significant since it impacts both the simplicity and expense of installation. If you want to furnish an existing home, a whole-house heater is probably your best option. Wiring and installing individual tankless heaters for specific appliances and gadgets in an existing structure can be more challenging and costly.

However, if your home is brand new, you have more flexibility in directing installation points. If this is the case, installing point-of-use tankless water heaters where you will need them the most might be a better option.

You might consider installing numerous point-of-use water heaters for various taps if you are building a new house. While the initial cost of acquiring and installing many point-of-use heaters is more than purchasing and installing a single whole-house heater, individual units will use less power over time, decreasing your bills in the long term. However, that is not to suggest that a whole-house unit is not the best energy- and cost-effective option for your home.

Remember that the flow-to-temperature-rise ratio is what ultimately determines this. The type of construction of your home and the number of appliances you need to heat influence this ratio.

Frequency of Use

When deciding between a whole-house or point-of-use water heater, another factor to consider is how frequently you will be using an appliance or device. If you need to heat water for an occasionally used guest bathroom or a Jacuzzi tub, a point-of-use device is generally the best option. On the other hand, a whole-house heater might be better for daily usage outlets like the kitchen sink and master bathroom.

The number of individuals at home and how often they visit determines the frequency. If you have a large family or a busy household with family members who are often home during the day and use a range of appliances, a whole-house tankless water heater is likely your best option. If you are a single individual who spends much time outside the house or travels a lot, point-of-use heaters are generally preferable.

Fuel Types

Whether you go for a whole-house or point-of-use tankless water heater, there are a few primary fuel sources to consider. Natural gas, liquid propane, or electricity power most tankless heaters.


Natural Gas or Liquid Propane

Both gas and liquid propane heaters work similarly, and both are more efficient and heat water faster than an electric tankless water heater. Electricity is more expensive than gas and propane. When it comes to powering a whole-house heater, a gas-powered tankless heater frequently makes the most sense because it only necessitates the installation of a solitary gas line.

If you choose a few point-of-use heaters, things get a little more complicated because you will have to provide gas to various areas, which is more labor-intensive and expensive. Most electric heaters can deliver a higher temperature rise per GPM than gas heaters (five gallons per minute instead of two).

Since gas and propane heaters often necessitate certain types of ventilation, they are the most acceptable options to consider when installing a new home or a remodel. Keep in mind that municipal gas service is not available in many places, and propane fuel must be stored in a holding tank on your property.


While gas water heaters are more economical, electric water heaters are easier to install and less expensive.

The greatest difficulties with electric tankless water heaters are the load they create on your home’s electrical system and the wire size required to safely and adequately power the device. Electric units are fine for point-of-use applications, but they should not be considered for whole-house applications due to the cost of electrical improvements.

  • Depending on the electric model, the manufacturer will specify the quantity and amperage of breakers required for the unit’s operation. Most residences have a 100 or 200 amp electrical service; according to the rest of the household’s electrical needs, you might get by with a small whole-house unit or a point-of-use heater without updating the electrical service. If you are inexperienced with your home’s electronic circuit or its demands, call an electrician before you buy.
  • All POU units, except the tiniest, will almost probably require a new breaker or two and new (thicker gauge) wire. DIYers with electrical abilities may be able to save money on some relatively simple upgrades, but everyone else should engage an electrician.
  • If the existing breaker panel is too small to accommodate the new water heater, you may have to add a subpanel. This will set you back at least a few hundred bucks, and it’s not a project for most do-it-yourselfers.
  • If your home’s electrical supply is inadequate, consider whether upgrading or adding a second service is worth it. Getting a second service or increasing the amps from 100 to 200 costs about $1000, but increasing the amps to 400 costs about twice as much. Depending on your home’s gas supply, investing in a gas-powered unit or revisiting traditional tank water heaters may be a better alternative.
  • On the other side, electric units do not need to be vented! This saves time, expense, and space while also allowing for a much greater number of installation locations.

Top Electric Tankless Water Heaters

Let us look at some of the best-rated electric tankless water heaters.


Steibel Eltron DHC Trend Point-of-Use Electric Tankless Water Heater

EcoSmart ECO 27 Electric Tankless Water Heater

The DHC Trend Point-of-Use electric tankless water from Steibel Eltron is exactly what it says on the tin. It is excellent at providing practically immediate hot water in a single spot. Steibel is frequently rated at the top of most rankings due to its low cost and high performance! Depending on your needs, you can choose from a variety of models. The DHC 10-2 is one of the most positively reviewed. It has a heating capacity of 32,757 BTUs and can offer up to six liters of hot water per minute.

Steibel Eltron has been creating water heating solutions since 1924, and their products come with a 10-year leak warranty and a three-year fault warranty. To generate 9,600 watts of heating output, this model uses 240 volts and a 40 amp circuit breaker. It has a flow rate monitor that shuts the electricity to the heating element in the case of a water supply breakdown to prevent burnout.

Rheem 18kW Tankless Electric Water Heater

Rheem 13kW Tankless Electric Water Heater RTEX-13

Rheem 18kW tankless electric water heater is popular due to its versatility. It produces 61,419 BTUs at 18 watts, making it suitable for use as a point-of-use warmer or a whole-house heater for a family of two. Hot water at a rate of up to 4.4 litres per minute is available. A nearly 100-year industry leader, Rheem backs it up with a five-year guarantee on heating components and a one-year warranty on other parts.

Electrical capacity for two forty amp breakers at 240 volts is required in your home. It is simple to own because of its 99.8% efficiency rating, self-modulating energy consumption, simple thermostat setting controls, and quick maintenance access.

Rheem 13kW Tankless Electric Water Heater RTEX-13

Rheem 13kW Tankless Electric Water Heater RTEX-13

Rheem’s 13kW tankless electric water heater is the smaller relative of our second place holder. It has all the same features that the bigger one has but in a smaller package. It is best for single-fixture or point-of-use applications.

Temperatures can be adjusted manually between 80 and 140 degrees Fahrenheit. Its 44,358 BTUs provide 3. With just one 60 amp breaker and 240 volts, you can produce 17 gallons of hot water per minute. The plumbing is easier because only ½ inch connections are required.

Eemax EEM24027 Electric Tankless Water Heater

Eemax EEM24027 Electric Tankless Water Heater

The Eemax 27kW electric tankless water heater is powerful enough for whole-house use at 27,000 watts. Up to five persons can use up to seven liters of hot water each minute for a low charge. If the inflow water is extremely cold, production can drop to barely three gallons per minute.

This water heater allows you to control the temperature in one-degree increments between 80°F and 140°F. Eemax provides a five-year leak warranty and a one-year parts warranty. The water flow rate is continuously monitored, and the power requirements are automatically adjusted. The installation will necessitate a space large enough to accommodate three additional circuit breakers.

EcoSmart ECO 27

EcoSmart ECO 27 Electric Tankless Water Heater

The EcoSmart name is known among pool owners for its tankless pool heaters. Their ECO 27 tankless water heater model has brought the technology indoors for whole-home use, and a limited lifetime warranty backs it.

The ECO 27 generates 92,128 BTUs using 27kW of power. This means three forty-amp breakers will be needed to power it. For most households of four or five people, a flow rate of 2.7 to 6.5 gallons per minute is sufficient. Temperatures can be adjusted in one-degree increments, and energy usage is self-modulating to save electricity.

Ecotouch Tankless Water Heater Electric

ECOTOUCH Point-of-Use Tankless Water Heater

Water heaters are one of the last products you would expect to include high-tech capabilities, but the Ecotouch water heater does just that. It has the appearance to match its high-spec functionality, with touch-based controls and a sleek design.

And it does not stop there with the high-tech features. The heater is equipped with a sophisticated mechanism that senses incoming water flow. If you are pumping less water than usual, the heater will reduce the heating temperature to keep the water at a safe temperature, so you do not scorch yourself.

It is convenient and hands-free, which is ideal if you despise having to control the temperature each time you shower manually.

Bosch Thermotechnology 7736505868, 4.5kW, Bosch US4-2R Tronic 3000 Electric Tankless Water Heater

Bosch Thermotechnology 7736505868, 4.5kW, Bosch US4-2R Tronic 3000 Electric Tankless Water Heater

Tronic 3000 is a point-of-use tankless water heater that is small enough to fit beneath sinks and is widely used to increase the amount of hot water in bathrooms and kitchens. It can be used to supplement the supply from a larger whole-house tankless water heater or a traditional water heater located distant from the sink. This Bosch model is only 13.75 × 13.75 inches in size and may be conveniently placed on a wall, shelf, or cabinet floor.

Although it is only built to accommodate one sink, it provides hot water on demand and saves energy by not heating and retaining water for later use. It also has an excellent energy efficiency rating of 98 per cent.

Sio Green SIO18 Electric Tankless Water Heater

Bosch Thermotechnology 7736505868

With 0.5 to 5.0 gallons per minute, the Infrared tankless water heater – Model Sio 18 is the high-end model for residential and commercial applications, excellent for large family homes or medium to large companies. This strong, efficient water heater uses Quartz Infrared heat exchangers and a tankless design for optimal performance and efficiency. Sio Green also offers a 2-year warranty.

The one significant disadvantage of the Sio Green SIO18 electric tankless water heater is that it does not create hot water as quickly as coil heaters. It will struggle to provide hot showers in the winter. Another minor issue is that the connectors are designed for the United Kingdom, and while they will fit US fittings, you may experience some leaking and need to replace the rubber washers.

Its features include:

  • Solid State Relay (SSR)
  • Intelligent Fuzzy Logic PID Thermostatic Temperature Controller
  • LED Temperature Outlet/Set Display (°F/°C setting),
  • LED Flow Indicator with 3 Digits (GPM)
  • Power Control with Full Modulation
  • Quartz Heating Elements with Multiple Redundant High Power Elements

Titan SCR2 N-120 Electric Tankless Water Heater

Titan Electric Tankless Water Heater

For the best value for money, the Titan SCR2 N-120 Electric Tankless Water Heater should be your go-to choice.

Being inexpensive, the Titan heater is also easy and simple to install if it is nearby to the electrical panel. The controls are simple, with only two buttons for adjusting the water temperature. It only switches on when it senses water flowing through it, resulting in significant energy savings.

The Titan SCR2 N-120 Electric Tankless Water Heater’s drawback is its poor flow rate, which makes filling the bathtub take a long time. The temperature swings a little in the initial few minutes as well.

Maintenance – Gas vs. Electric Tankless Water Heaters

Regular maintenance is required for all water heaters; whether or not we decide to do it is different.

There is no getting around it: gas tankless water heaters require more maintenance than electric systems. Let us look at each one:

Gas Tankless Maintenance Requirements

In tankless gas systems, mineral scale build-up is extremely frequent. Water contains minerals such as calcium and magnesium, and the higher the concentration of these minerals, the “harder” the water.

Mineral scale (also known as limescale or scale) piles up in your tankless water system faster when more minerals are in the water.

As the scale within the tankless device builds up, the heat exchanger is compelled to work harder than necessary. The system may eventually overheat and shut down as a result of this.

Even if the tankless system does not shut down, scale creates additional stress on the appliance, lowers energy efficiency, and shortens its service life!

Hard water/mineral scale accumulation is the number one enemy of gas-fueled tankless water heaters.

If you live in a hard water area, you should frequently clean your tankless heater. The owner’s manual is the best source of information for your specific tankless model’s maintenance requirements.


In addition to normal flushing of scale build-up, a skilled technician should inspect a gas-fueled tankless water heater once a year to ensure safe fuel combustion and that the system is working properly.


Electric Tankless Maintenance Requirements

Electric tankless water heaters require little upkeep. Apart from cleaning the water inlet filter on a routine basis and draining the limescale once in a while, these systems don’t require any more maintenance.

Indoor vs. Outdoor Units

Finally, consider whether an indoor-outdoor tankless water heater is the right choice. An indoor heater is installed within the house, and an outdoor heater is placed outdoors. However, what are the benefits and drawbacks of each?



An indoor heater cannot be impacted by climate events or the elements. Condensation will build on and around your heater. Thus an inside installation will necessitate venting linked to a drain to remove the condensation from the heater and out of your home. Indoor heaters, installed vertically or horizontally, require ventilation piping (to direct airflow).



Because it is self-ventilating by a natural breeze, an outdoor heater does not require extensive ventilation. Outdoor heaters are built to withstand harsh weather conditions such as snow, rain, and wind.

On the other hand, an outdoor tankless water heater demands care and maintenance. When the weather dips below freezing, remember to drain the unit to prevent water freezing in the tank.

Whether you should use an indoor or outdoor heater relies on whether you live in a new or old residential building. Existing homes benefit from outdoor tankless water heaters because they require fewer plumbing and ventilation changes. An indoor heater may be more appropriate for a new building or renovation because you can design your home around it rather than squeeze your heater into your current home, which can be time-consuming and costly.

Finally, while determining which tankless water heater is best suitable for your home and family, many factors must be considered. Keep the following factors in mind when you make your decision:

  • Construction kind (new/remodelled or existing).
  • Weather and climate in your area of residence Household customs and lifestyle.
  • You will need to heat a certain number of gadgets.
  • How frequently will you use each of these devices?
  • For your family, prioritizing cost, efficiency, and maintenance.


Tankless Water Heater Advantages

Rheem 13kW Tankless Electric Water Heater RTEX-13

The benefits of having a tankless water heater are numerous. Take a look at a few examples:

  • Energy Savings / Operating Costs: Since hot water is given on demand, standby heat loss is virtually eliminated. Tank-style water heaters store water in a tank that is heated and reheated as needed.
  • Replaceable Parts: Tankless water heaters are meant to be repaired, so their service life is extended in part. If a tank-style water heater starts to leak, the entire heater will almost certainly need to be replaced. Tankless water heaters, on the contrary, are built with virtually every component replaceable.
  • Unlimited Hot Water: The capacity of your water heater’s storage tank no longer determines the length of your shower. A tankless water heater, when properly sized, can deliver an endless supply of hot water to your household.
  • Fresh Water: Hot water should never be stored in a tank with rust or mineral scale tank. When hot water is required, it is promptly heated and delivered.


Tankless Water Heater Disadvantages

There is no arguing that there are many upsides to tankless water heaters. However, like everything, they are not flawless. Here are a few of the disadvantages of owning a tankless system:


  • When choosing a tankless water heater, expect to pay more money upfront. These units can cost up to three times as much as a tank-style water heater when installation fees are factored in.
  • Upgrade the power – Electric tankless water heaters use electricity to deliver hot water. Many properties, particularly older homes, may not sustain a tankless water heater without changing their electrical system.
  • Costly venting: Non-condensing gas-fueled tankless water heaters necessitate the use of costly category III venting material.
  • Limitations in Output: If the household’s hot water demands exceed the system’s capacity, the appliance will not be able to provide adequate hot water. A tankless water heater can only produce as much hot water as it can heat at any given time since it lacks a storage tank. This is why sizing a new tankless system correctly is so important.


DIY vs. Hire a Professional

A tankless water heater is not a do-it-yourself job. Your home may need to be upgraded to suit your new water heater, which most often necessitates the installation of new wiring or gas lines. Because dealing with gas and electricity is extremely dangerous, we strongly advise you to leave this project to the professionals.

Some localities even demand that water heaters be installed by a professional. An expert will be familiar with all current codes regarding carbon monoxide emissions, thermal resistance, venting, and other issues.

Hire a qualified plumber or water heater specialist to install your water heater while adhering to applicable codes and permits. Most specialists can also ensure that you obtain the correct water heater for your property, saving you time from trying to install an unsuitable heater.


Our top pick and the most positively rated tankless water heater is the Steibel Eltron DHC Trend point-of-use, which will consistently deliver the hottest water to the most points in your home. It also has continuous flow technology, which slows down the water if you empty it too quickly, ensuring that you never run out of hot water.

The Titan SCR2 N-120 electric tankless water heater should be your go-to choice if you have a tight budget and do not mind waiting for the tub to fill. It is also our pick for the finest tankless water heater for the money.

We hope this guide has left you well equipped with the knowledge and know-how of electric tankless water heaters. So the next time you go out to buy one for your home, you will know exactly what to look for!

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