Tankless Electric Water Heaters
Buying Guide and Best Models

A review of the popular tankless electric water heaters from the US and Canada - designed for on-demand heating of potable water. Find out about the benefits, advantages and compare the features. A review of top sellers: Stiebel Eltron Tempra, Rheem, and EcoSmart.

One is common for all-electric tankless hot water heaters; they use electric heating elements to heat water, on-demand and in continuous supply.

Electric tankless heaters are small, lightweight, and compact heating appliances that can be installed on the wall, under the sink, in the bathroom or kitchen, and typically close to the point of use. The greatest advantage is that the standby heat loss, as found in tank-type heaters, is eliminated, which allows them to achieve high energy factors.

According to the manufacturers, tankless electric units save more energy when compare to tank-type and have lower installation costs. Of course, with on-demand heating and fast water delivery, you will appreciate the comfort and convenience more.

Best selling models


Electric tankless water heaters are designed to deliver hot water to low-demanding applications (single fixtures) and whole-house (multiple fixtures), either in a warm or cold climate. Most models can work in the range from 80 to 140 F or more when used in commercial applications.

Whole-house electric water heaters can easily replace storage tank-type models, providing more floor space for other use. These are usually wall-mounted and centrally located, providing hot water to more than one fixture.

Point-of-use water heaters (POU) are designed to deliver hot water to one fixture and are installed either above or below it and, most of the time, under the sink. These are used for distant sinks to avoid long runs of plumbing pipes in cottages, apartments, garages, small offices, and businesses.


  • Small and compact size
  • Heated water is clean and fresh
  • Longer life
  • No standby heat loss
  • No standby heat loss
  • Less prone to rusting, corrosion and water leaking
  • Cheaper than gas models
  • Easier to install as there are no venting and gas pipes required
  • Great flexibility allows installation in places where the gas model cannot go
  • Fewer components to service or maintain
  • Less impact on the environment – all the components can be replaced
  • Safe – no exhaust gases and gas leaks


  • Existing electric service might need an upgrade or full revision - which can be very costly
  • A unit has to be wired directly into the home's main electrical panel
  • Electricity is more expensive than gas
  • It might not be suitable for colder regions
  • Limited volume of available hot water
  • Cold water sandwich effects are frequent, so your daily habits have to be modified

Popular models

Stiebel Eltron Tempra 24 Plus

Stiebel Eltron 24 Plus TempraStiebel Eltron 24 Plus Tempra

Stiebel Eltron is the German manufacturer of tankless electric water heaters that offer quality models for point-of-use service and whole-house water heating.

Stiebel Eltron Tempra 24 Plus is the top-selling model that can be used almost anywhere, from one to two fixtures in colder areas or up to 3 showers in warmer regions, operating simultaneously.

Stiebel Eltron Tempra 24 Plus is the most advanced electrical tankless water heater from this company, providing hot water on demand and in endless supply. So no matter how long it takes you to shower, hot water is always there – for you and those after you.

The heater utilizes heavy-duty electronics, a microprocessor, and advanced flow control. It ensures the constant temperature of hot water no matter the water flow (the minimum is still required to operate).

Tempra 24 Plus utilizes only quality elements such as solid copper heating elements. The combined work of the microprocessor, flow sensor, and built-in inlet and outlet temperature sensors will result in modulating operation where the heating elements are engaged in stages. This means that more power is provided for higher water flow and less for lower flow – trying to meet the set temperature with the least amount of energy. The power is at any point of time monitored and adjusted automatically.

Tempra 24 Plus uses the digital display to show the temperature of hot water and error codes when the problem occurs.

According to the manufacturer, it is built to replace the tank-type unit, saving up to 20% energy and lots of space.

It comes with a 7-year warranty against leaks.

Rheem RTEX-24

Rheem RTEX-24Rheem RTEX-24

One of the top sellers from Rheem tankless electric water heaters is the RTEX-24 model.

As other advanced models, Rheem RTEX-24 is also equipped with modulating power control, so more energy can be saved when adjusting the power and water flow. It is equipped with the 3 heating chambers made of copper for better corrosion resistance, controlled by the microprocessor for precise and comfortable heating.

The unit's digital temperature control is conveniently located at the front of the unit. It allows users to adjust the temperature between 80 F and 140 F, with the increment of 1 F, making the water temperature accurate to the desired and very comfortable to use. As the standby heat loss is eliminated, the water heater can generate a stable temperature and efficient operation, where the efficiency is 99.8%.

The RTEX-24 model can provide up to 5.9 GPM of water flow, sufficient even for homes with multiple showers.

EcoSmart ECO 24

Ecosmart ECO 24Ecosmart ECO 24

EcoSmart ECO 24 is the medium-sized electric tankless water heater recommended for mid-to-large-sized homes as it can heat up to three showers and two sinks simultaneously in a warm climate.

Also, as long as the minimum water flow of 0.3 GPM is met, the water heater can easily operate when the small (point-of-use) or a large amount of hot water (whole-house) is needed. At the temperature rise of 77 F, the water heater can provide the maximum water flow of 5.9 GPM, as the Rheem's RTEX-24, where the temperature of hot water could range from 80 to 140 F.

According to the manufacturer and due to the self-modulating technology, ECO 24 can provide up to 60% in energy savings.

The unit comes with a limited lifetime warranty on electronics and heat exchangers, but only when used in residential applications.

At the time of writing this article, EcoSmart ECO 24 (with other 5 models) had over 2000 reviews, where over 80% are positive.

Buying tips

Features to look for

  • Modulation
  • Advanced water flow sensor
  • Microprocessor
  • Digital temperature display
  • Dial control
  • Copper, brass and stainless steel components
  • Simple installation with standard connections (3/4")
  • Tight temperature increment

Hot water usage in gallons per minute (GPM)

  • Whole-house – up to 6 GPM
  • Kitchen sink – up to 2 GPM
  • Bathroom shower – up to 2 GPM
  • Dishwasher – up to 2 GPM
  • Washing machine – up to 1.5 GPM

Electric tankless water heaters installation tips

Tankless electric water heaters are designed not only for one single fixture – some can be used for the whole-house water heating, but it depends on some factors such as the temperature of incoming water and power of the unit. That is why bigger models can easily replace tank-type models.

Electric tankless are small, but they can still use one, two, three, or more heating elements, and since they draw more Amps, the electrical panels might need an upgrade. Moreover, the unit must be hardwired to the panel.


As seen from the above, small tankless electric water heaters are heating water on demand and supply hot water to either one single sink/shower or multiple fixtures and are the perfect supplement to an existing system that cannot satisfy user requirements. The heaters also work great in conjunction with the solar and geothermal water heating systems.

Due to the small and compact design, they are easy to install – usually under the sink, in the bathroom or kitchen, or wherever hot water is needed fast. Electric and tankless water heaters just need water and electrical supply, making them very safe. There are no gas connections or venting pipes, providing more flexibility during the installation.

Tankless electric water heaters are perfect not only in residential homes, cottages, cabins, apartments but in commercial applications such as office buildings, stores, restaurants, schools, hotels, motels, factories...