All about instantaneous water heaters! >

All about instantaneous water heaters

Why instantaneous water heaters?

Why instantaneous water heaters?

Interesting facts about instantaneous water heaters
For hot water supply, decentralized instantaneous water heaters have many advantages, which make them particularly suitable for new construction and replacement in existing buildings compared to expensive central systems, such as gas boilers. We show you how instantaneous water heaters perfectly combine comfort and efficiency.

Some instantaneous water heaters stand out for their particular efficiency, ease of use and high level of comfort and have therefore received awards. On the page award-winning instantaneous water heaters you will find an up-to-date overview of instantaneous water heaters that are suitable for typical applications. There are recommendable models in every price range with different equipment and numerous functions.

Use the interactive online product advice!

In the following, all relevant aspects of decentralized hot water supply are considered and comprehensive information is provided on the various types of instantaneous water heater.

In recent years, experienced manufacturers (e.g. CLAGE from Lüneburg) have developed and launched modern and innovative devices on the market. With house new building or reorganization energy-efficient flow heaters are ideally suitable for the supply with warm water for hand wash basin, kitchen sink or the complete bath supply, also with several withdrawal places. The main focus is on energy efficiency, ease of use, simple installation and high product quality.

What is an instantaneous water heater?

Instantaneous water heaters are permanently installed devices for heating water. They heat the water only when a draw-off fitting is opened. The cold water is heated to the set temperature in the device as it flows through. Instantaneous water heaters can provide hot water indefinitely. In contrast, storage water heaters and boilers only hold a limited amount of hot water in stock, which is a major disadvantage.

There are electrically powered and gas powered instantaneous water heaters, as well as fresh water stations. On this page, electric instantaneous water heaters are the main topic. Other names are instantaneous water heater, geyser or instant water heater.

Where are instantaneous water heaters used?
For which applications are there instantaneous water heaters?

Instantaneous water heater for the hand basin / guest toilet

Instantaneous water heater for the hand basin / guest toilet

Only small amounts of hot water are needed at the sink and a temperature between 35 and 38 degrees is sufficient for washing hands. Therefore, small instantaneous water heaters with 230-volt connection from the M series are the best solution, whether in a private home or office building. Mini instantaneous water heaters in modern design are cost-saving as well as space-saving and are very easy to install.

> to the MCX product page
IWH for the kitchen sink

IWH for the kitchen sink

In the kitchen, hot water is needed for washing up and cleaning, and sometimes it has to be 60 degrees hot. The powerful yet very compact instantaneous water heaters of the C series also impress with their ease of operation (e.g. with a remote control) and their energy efficiency. They can be installed in a space-saving way under or above a kitchen sink and also supply hot water in seconds at a sink in the utility room.

> to the CFX-U product page
Instantaneous water heater for the shower

Instantaneous water heater for the shower

On average, we take a shower for three to five minutes, even if the process seems longer to us. Particularly when showering, we want the personal feel-good temperature, ideally without lengthy setting and mixing, but quickly to the exact degree. The comfort instantaneous water heaters of the D series offer exactly the comfort we want from a modern wellness shower bath.

> to the DEX Next product page
Instantaneous water heater for the bathroom

Instantaneous water heater for the bathroom

Powerful instantaneous water heaters with up to 24 or 27 kW can supply an entire bathroom with several taps at the same time and are still energy efficient. D-series electronic instantaneous water heaters are also a very good choice for bathroom renovation. The very powerful design devices can be installed quite classically on the wall or hidden in a bathroom cabinet or behind an inspection opening. In this way, they fit perfectly into any bathroom.

> to the DSX Touch product page
IWH for special applications

IWH for special applications

For special applications we also have specialized instantaneous water heaters in our program:

> For tapping points with particularly high hot water requirements (up to over 25 liters per minute), e.g. a rain shower/wellness shower: > to the DSX Touch Twin product page

> For reheating and hygienic drinking water supply in an apartment by means of an apartment transfer station with integrated electric instantaneous water heater: > to the WS-Hybrid product page

How to find the right instantaneous water heater:
The online product advice helps!

Typical questions are e.g.:
- Are you looking for a unit for single or group supply?
- Do you have 230 volts or 400 volts available?
- Do you have specific wishes regarding the equipment, e.g. a remote control?

... or other factors? No problem!

With our interactive product advice, you will receive suitable product suggestions for your specific application with just a few clicks.

> to the hot water product advice

What are the different types of instantaneous water heaters?

Small instantaneous water heater

Small instantaneous water heater

How long do you wash your hands? It is rarely longer than 10 seconds. With such a short duration, it makes sense to get the water at the desired temperature as quickly as possible. This is no problem with the mini instantaneous water heaters with 230V or 400V: they are shapely, space-saving and hardly noticeable under the hand wash basin and in the tea kitchen.

> Overview small instantaneous water heaters

Compact instantaneous water heater

Compact instantaneous water heater

Nomen est omen: these water heaters shine where there is little space, but still need hot water up to 60 degrees. The most popular are these instantaneous water heaters for installation under the kitchen sink. But this very flexible product class can also be used under double sinks, at cleaning sinks in the boiler room or for smaller showers.

> Overview compact instantaneous water heaters

Comfort instantaneous water heater

Comfort instantaneous water heater

This type of instantaneous water heater is rightly named because it is all about comfort: plenty of hot water and many convenient functions. Comfort instantaneous water heaters are powerful and can supply a complete bathroom, an entire apartment or, if required, an entire house with pleasantly warm water at the exact temperature.

> Overview comfort instantaneous water heaters

IWH with Smart Control

IWH with Smart Control

Anyone who wants to install their instantaneous water heater invisibly in a cabinet or behind a pre-wall will want convenient remote control of the devices. There are various smart options for this via WLAN, Bluetooth, radio remote control or voice control. Several instantaneous water heaters in the house or apartment can also be networked with each other

> Overview of instantaneous water heaters with Smart Control

Advantages of instantaneous water heaters

  1. Immediately up to temperature

    According to demand and without waiting times

  2. Desired temperature

    No mixing of cold water

  3. Saves operating costs

    Energy-saving technology

  4. Environmentally friendly

    Less energy and water consumption

  5. Efficient

    Energy and circulation losses are eliminated

  6. Short pipe runs

    Installed directly at the tapping point

  7. More hygiene

    due to short line distances

  8. CO2 down

    The share of renewable energies in the electricity mix increases

For all water and energy savers!

You want a hot water supply that is hygienic, accurate to the degree and comfortable? And of course efficient and economical? That is possible! With electric instantaneous water heaters from CLAGE.

> Start video

Differences from other hot water systems

Differences to decentralized storage

Differences to decentralized storage

Hot water tanks: Everyone knows them. In many German households there are still "storage water heaters" with a capacity of 5 liters, 10 liters or more. But are such hot water heaters still up to date? These storage water heaters partly consume a lot of standby energy and are therefore currently rightly questioned.

It is advisable, for example, when purchasing a new storage water heater or replacing an existing one, to find out about sensible alternatives: What can be taken instead of a storage tank for decentralized hot water supply? Read our comparison:

> Comparison: storage tank or instantaneous water heater?
Differences from the central hot water supply

Differences from the central hot water supply

When deciding whether to use a centralized or a decentralized solution for the hot water supply of a building, various factors have to be taken into account.

So the investment costs, the installation effort, the pipe lengths, the comfort as well as the energy and water consumption play decisive roles. The system should also provide hot water for the individual applications at the right temperatures and in sufficient quantities, ideally even for an unlimited period of time while still being economical.

First compare, then decide!

> Hot water: centralized or decentralized?

Downloads on the topic

Instantaneous water heater catalog: > download (PDF)
Hot water guide for house construction: > download (PDF)
Product and price list: > download (PDF)
You will find further documents in our media center.

In which buildings are instantaneous water heaters used?

Instantaneous water heaters are used in private, commercial and public buildings worldwide. Building owners, tradesmen, architects, planners and investors rely on our expertise and special service in the field of energy-efficient water heating.

With our wide range of products, we almost always have a suitable and intelligent solution for hot water supply. Our products can be found in renowned hotels, in office buildings, in modern architect's houses and everywhere where you do not want to do without efficient hot water comfort.

CLAGE instantaneous water heaters are innovative, technically high-quality and versatile.

In which buildings are instantaneous water heaters used?

Private households

Electric instantaneous water heaters are used in almost all residential properties: in single-family and multi-family houses and, of course, in apartments. Both in existing buildings and in new construction or renovation projects, it makes sense to rely on decentralized hot water technology with modern instantaneous water heaters. Whether at the hand basin, in the kitchen or in the bathroom: instantaneous water heaters provide more energy efficiency and comfort at home.


When buildings with outdated technology are renovated, the question of modern and more energy-efficient heating and hot water technology arises. In new buildings, the heating requirement continues to fall as a result of technical progress. To generate the highest potential savings, the heating and hot water supply should be completely separated. Electric instantaneous water heaters are an energy-efficient and hygienic solution.

Commercial and office buildings

E-mini instantaneous water heaters at hand-washing sinks for employees, customers and visitors make the WC more comfortable. Our energy-efficient devices directly at the tapping point are the optimal solution in large buildings with long pipe runs.


E-flow water heaters are used in hotels, resorts and restaurants. You can even find our Zip water systems on cruise ships.


Here, for example, workplaces and staff showers can be equipped with electric instantaneous water heaters. We also have special devices in our program for special requirements.

Public buildings

Highly frequented WC rooms in public areas should be equipped with efficient instantaneous electric water heaters. Combined with appropriate fittings, optimum hygiene and corresponding savings are achieved.

"Everyone wants to save energy. To do this, we recommend separating heating and hot water. The heating system can thus be designed smaller and become more efficient. Compared to the usual central supply, the use of decentralized instantaneous water heaters can save up to 40 percent energy."

JörgA. Gerdes, Managing Partner CLAGE GmbH

Commercials of top products

The hygienic premium duo.

The hygienic premium duo.

MBX Lumino: Energy-efficient instantaneous water heater and sensor tap in a set for maximum convenience. With multicolor LED color light ring, hygienic flush and one-pipe system.

> Start video
Convenient to use, even at the kitchen sink.

Convenient to use, even at the kitchen sink.

CFX-U: The included wireless remote control makes it easy to set the temperature, even if the instantaneous water heater is installed under the sink.

> Start video
Our best IWH!

Our best IWH!

DSX Touch: Fully electronically controlled high-tech instantaneous water heater with real glass touch display and Bluetooth remote control for convenient and economical hot water supply.

> Start video

Which instantaneous water heater do I need for what?

Instantaneous water heaters are becoming more and more popular! This is partly because they are very flexible to use. On the other hand, instantaneous water heaters save space and energy and can provide hot water indefinitely.

We have compiled the most common applications for instantaneous water heaters in this table.

Applications Small IWH Compact IWH Comfort IWH
Warm water for washing hands
Warm water for washing hands and dishes
Plenty of hot water for showering, bathing, washing hands and washing up
Warm water from 35°C to 42°C
Warm water from 20°C to 60°C
Hot water for a single hand basin
Hot water for several hand basins
Warm water for a full bath (basin, showre, bath tub)

Note: With the help of our dynamic online product advice, you can find suitable products for your very individual application.

What do "fully electronic", "controlled" and "hydraulic" mean?

Fully electronically controlled

Fully electronic instantaneous water heaters possess apart from the sensors also still another motor valve, with which the flow rate cannot only be measured, but be regulated additionally still. Thus the equipment can always hold the adjusted temperature under all conditions on the degree exactly constant.

These Top devices can possess in addition also still further attractive equipment features:
> Digital announcement e.g. for temperature, time, flow quantity, energy consumption, energy costs etc..
> Remote control (radio or Bluetooth)
> ECO function for energy-saving operation
> automatic tub filling, wellness or shower programs
> memory keys with individually adjustable desired temperatures
> safety functions, e.g. scald protection and child safety device

Electronically controlled DLE with three sensors

In devices with three sensors, the temperature can be set individually in small steps (1 degree or even 0.5 degrees). They measure the temperature of the incoming cold water, the flow rate and also the temperature of the heated outgoing water.

This means, for example, that there is no need for a thermostatic fitting in the shower: even if water is suddenly tapped at another tapping point, the temperature remains almost the same during showering.

The main advantage here is that the temperature no longer has to be controlled via the mixer or by adding cold water. Thus these devices are more energy-saving and more water-saving.

Electronically controlled DLE with two sensors

With two sensors, the temperature can be selected in factory preset levels. The two sensors measure the temperature of the incoming cold water and the flow rate. The power required to heat the water to the set outlet temperature level is then calculated.

This means that the set outlet temperature can be kept more constant than with hydraulic instantaneous water heaters in the event of pressure fluctuations, inlet temperature changes and voltage fluctuations.

Hydraulically controlled IWH, no sensors

As soon as water is tapped at a faucet, it flows through a water quantity regulator in the instantaneous water heater. This attempts to compensate for the pressure fluctuations in the water line: Pressure fluctuations can occur in the mains network if, for example, a second tap is opened. However, the heating capacity of the hydraulic instantaneous water heater remains constant in the event of a pressure drop, which then causes the water temperature to rise. A flow switch then detects the amount of water flowing through, activating one or more heating coils, which then heat the cold water.

Hydraulic models often heat the water hotter than it is actually needed. Cold water must then be added. With the same usage pattern, these instantaneous water heaters have an approx. 20 percent higher energy consumption.

Storage tank or instantaneous water heater?

Storage tank or instantaneous water heater?

When comparing electronic instantaneous water heaters and storage water heaters (or conventional hydraulic instantaneous water heaters), the most important questions are:

> Which system has more advantages?
> Are instantaneous water heaters more efficient than storage tanks?
> Do instantaneous water heaters also consume stand-by energy?
> Why are storage tanks significantly larger than instantaneous water heaters?
> Why can instantaneous water heaters provide hot water indefinitely?
> Do storage tanks offer the same comfort as instantaneous water heaters?

Read our detailed comparison between storage tanks and instantaneous water heaters.

FAQ / Frequently Asked Questions

In our FAQs, the frequently asked questions, you will find interesting information on many topics, e.g. the following questions:

> How does an electric instantaneous water heater work?
> Do instantaneous water heaters have to be vented?
> Can instantaneous water heaters also be used for reheating?
> Do you have to descale an instantaneous water heater?

> to the FAQ

The new online calculator:
Calculate hot water values easily

The hot water calculator illustrates the relationship between the three important hot water variables: Temperature, flow rate and device capacity. Among other things, it can be used to calculate the achievable temperatures and water volumes. The tool thus helps with advice, e.g. in the search for a suitable product for a specific hot water application.

The cold water temperature can also be taken into account. This allows different conditions to be represented, such as cooler inlet temperatures due to colder seasons or higher inlet temperatures in warmer countries. This also enables the consideration of a hot water supply with a pre-heating system, e.g. solar thermal.

In addition, energy consumption, total costs and CO₂ emissions of an application can also be calculated. Additional input fields are available for this purpose: Electricity costs, tapping duration and frequency of use.

> to the hot water calculator
The new online calculator:<br>
Calculate hot water values easily

Installation videos: We support you during the installation!

Installation video MBH

Installation video MBH

As an energy-saving standard solution for installation with all normal faucets, the flameproof electric instantaneous water heater MBH (with 230V or 400V) is offered. The connection set included in the scope of delivery facilitates installation directly to the faucet. And hot water flows as soon as it is needed.

> Installation video MBH
Installation video CEX-U

Installation video CEX-U

With its electronic control, the CEX-U ensures an energy-efficient hot water supply in the kitchen. The temperature is set using the sensor keys on the control panel. The LED display shows the selected temperature. Two fixed value buttons are factory programmed with 35 °C and 48 °C. The unit can be installed with both pressure-resistant and non-pressure fittings.

> Installlation video CEX-U
Installation video DCX Next

Installation video DCX Next

The DCX Next electronic comfort instantaneous water heater impresses with its simple operating concept. One of the five typical hot water temperatures can be selected at the touch of a button. This is indicated by an intuitively understandable signal color.

> Installation video DCX Next
CLAGE channel on Youtube

CLAGE channel on Youtube

Visit our channel on Youtube. We have easy to understand installation videos for almost all of our products, showing the main steps in the installation of an instantaneous water heater, such as connecting a device.

> CLAGE channel on Youtube

Tip: Looking for extensive and detailed installation instructions? Download the instructions for use and installation in our media center!

Contact options



+49 4131 - 8901-0

We will be happy to answer your questions on the phone and advise you on hot water topics.




You are also welcome to e-mail written inquiries to us.

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Visit us.

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Opening hours:
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Pirolweg 4
21337 Lüneburg

Appointment for consultation:
+49 4131 - 8901-0

As a specialist for decentralized hot water supply, we offer a wide range of products with many individual solutions. For us, everything from A to Z has to do with hot water. We are the market leader for small instantaneous water heaters and as an experienced manufacturer we are constantly looking for new hot water solutions for hand basins, kitchens or bathroom supply.

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