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Compact electric water heater or how to earn m2?

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The smallest electric water heater possible!

This article discusses compact electric water heaters of small capacity and not instant electric water heaters (or tankless) that are subject of another article.

We bring you the latest innovations in terms of mini water heater or small capacity water heater, i.e.  from 10 litres to 40 litres. Note, an adult consumes 50 L per day in average.

mini-cumulus-accumulation 15 litres

The capacity and the heating time…

The “micro storage water heaters” are adapted to basins, sinks and showers where the distance between the boiler and the draw-off point is too important. They avoid wasting cold water contained in the circuit until hot water arrives to the draw point.

If your heating system can be independent of your domestic hot water (DHW) production circuit, this solution might be interesting from an energetic point of view as only very small amount of water is heated.

The water heating temperature is between 50°C to 60°C for sanitary hygiene reasons. It is reduced by the addition of cold water at the tap. It is usually not adjustable. Run the water heater during off-peak hours to limit your consumption (off-peak hours or day/night switch and an adapted subscription).

If you are in a limestone area, think of a steatite resistant water heater (protected by a sheath), or a titanium/magnesium anode, in order to avoid limescale building-up and therefore the reduction in efficiency.

Simple installation to carry out according to the standards

The hot water production electrical circuit is protected according to its power, generally, by a 20A circuit breaker, a differential device of 30 mA and power cables of 2.5 mm2. The standards require grounding all metal (copper) hydraulic distribution sections.

Provide space related to the security unit to associate with the water heater. This serves to protect the tank from the water heater against pressure excess and prevents any hot water return into the cold water circuit. The security unit drain port is to be connected to a drainage via a siphon kit.

Price ranges for quality products are between £200 to £500 for one 30 litres tank.

Mini electric storage water heater
Washbasin Piecemeal use: less than 20 seconds. Flow rate: 2 litres per minute. Need: 10-15 litres tank on or under the sink. Average heating time: 10 litres in 20 minutes. 15 litres in 30 minutes. Dimensions: Ø x H x P (cm) : 34 x 40 x 35 cm
Sink Piecemeal use: 2 minutes. Flow rate: 5 litres per minute. Need: 30 litres tank on or under the sink. Average heating time: 30 litres in 50 minutes. Dimensions: Ø x H x P (cm) : 34 x 62 x 35 cm
Shower Piecemeal use: less than 5 minutes. Flow rate: 8 litres per minute. Need: 40-50 litres wall or floor mounting tank. Average heating time 40 litres in 80 minutes. Dimensions: Ø x H x P (cm) : 34 x 40 x 35 cm

Choose a model with vertical or horizontal installation depending on your configuration.

Chauffe-eau électrique connecté – 2250W – Plat Multiposition – 40L

15 litres ou 30 Litres 2000W

What kind of innovations does a compact water heater bring?

With the new models:

  • There is no need to hide your water heater, it becomes design (almost flat, compact, etc).
  • The volume is reduced (starting from 10 litres) as well as the size.
  • The heating time is reduced (starting from 20 minutes).
  • Choose an energy rating label – B (at least).
  • Maintenance is reduced to minimum or even zero maintenance (no more resistor change throughout the life of the device).



The French society VIESSMANN is one of the world’s leading manufacturer of heating and cooling system. The company of 12000 people in over 70 countries, develops particularly domestic hot water DHW production systems through innovative and efficient water heaters. With only 24 cm of thickness the CEI model, is very compact and fits into any room in the house (-50% of floor surface comparing to a traditional water heater). This new innovative model consists of 3 stainless steel tanks. Only the quantity of water required is heated. Significant savings on consumption and maintenance are possible.



The Italian manufacturer ARISTON, develops a range of instant water heater and small capacity water heater (starting from 15 litres). The mini water heaters are able to heat your water (with a difference of ∆T=40°C between the temperature of incoming water and the comfort temperature) in less than 30 minutes. Their compact dimensions are adapted to an under-sink installation.


mini storage water heater Ariston 15 L



The French manufacturer THERMOR, develops a range of micro storage water heater of 10 litres, 15 litres, 30 litres.

thermor micro ballon extra plat

THERMOR micro slimline water heater 40 L



NIBE is a Swedish industrial group developing a range of boilers, heat pumps and micro storage water heaters of 15 litres.


NIBE micro water heater 15 L


Compact electric water heater, or how to earn m2?
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