Opinions on the Dietrich Alezio S Compact air/water heat pump

Opinions on the Dietrich Alezio S Compact air/water heat pump

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Just hearing the brand name de Dietrich makes you think of Deutsche Qualität, but everyone knows it's French, right? The de Dietrich brand is a big name in heating in France.

It all started at the end of the 17th century when the ancestor Jean de Dietrich acquired a forge in a small village of the Natural Park of the Northern Vosges: Jaegerthal.

It is a very picturesque place typical of the small villages of Alsace in a green setting and in which you can still visit the ruins of the forge.

One thing leading to another, the family has undertaken many projects and has built up a industrial empire, in the field of railway (now sold to Alstom Reichshoffen), in the field of heating and later in the industry chemical and pharmaceutical.

If you want a quote for this machine, you can can ask our network of installers in France or Belgium by filling in the form below

Jean de Dietrich's son was even the first mayor of Strasbourg after the Revolution, and commissioned the French anthem "La Marseillaise" from Rouget de l'Isle. This shows the deep links of this family with the history of France!

The de Dietrich thermal brand has its headquarters in Mertzwiller in the Bas-Rhin (67), just next to Reichshoffen and Niederbronn-les-Bains. It specializes in heating systems, boilers, wood stoves, heat pumps, water heaters, and also offers solar and air conditioning solutions.

This brand is part of the BDR Thermea Group, which brings together several companies specialized in heating around the world, including the French company Chappéethe Belgian company Remehathe German company Brötje HeizungTurkish society Baymakand Baxi water heater specialists in the UK. You will find that many of these companies offer Dietrich products under different names.

We are interested in the air-water heat pump model of Dietrich Alezio S Compact which can be seen on the picture above. You can see the outdoor unit (for the garden) on the left, the indoor module on the right, grafted on top of the hot water tank.

This is a model that is found a lot in Alsace naturally, since the brand is of Alsatian origin and very active in the region. But the product can also be found all over France, and in the world through the partners of BDR Thermea Group.

Aesthetics of the de Dietrich Alezio S Compact

subjectively, the outdoor unit seen in the photo above is quite compact and the ventilation grid fits well. As for the indoor unit and the tank, which are connected together, they are meant to be placed in a closet, so it doesn't matter how they look.

The idea of this compact split air water heat pump is to fit into a modern environment, in a kitchen cupboard for example, as you will see in the video below.

Performance Alezio S Compact by Dietrich

This heat pump is available in 5 power variants, depending on your heating needs:

  • Alezio S Compact 4.5 MR/EM
  • Alezio S Compact 6 MR/EM
  • Alezio S Compact 8 MR/EM
  • Alezio S Compact 11 MR/EM or MR/ET
  • Alezio S Compact 16 MR/EM or MR/ET

EM = single-phase electricity and ET = three-phase electricity

The range of heating power allows to adapt as well to a small apartment, as to a BBC house, or to a traditional house less well insulated and of bigger surface.

These are the powers and COPs in heating mode.

Alezio Compact 4.5 MR EM

Air / Water35°C (Power / COP)45°C (Power / COP) 55°C (Power / COP)
-10°C4.03 kW (2.27)3.69 kW (1.77)
-7°C4.40 kW (2.46)4.02 kW (1.91)3.50 kW (1.34)
2°C3.50 kW (3.04)3.50 kW (2.55)3.50 kW (1.91)
7°C4.50 kW (5.06)4.50 kW (3.70)4.50 kW (2.70)

Alezio Compact 6 MR EM

Air / Water35°C (Power / COP)45°C (Power / COP) 55°C (Power / COP)
-10°C4.86 kW (2.42)4.13 kW (1.87)3.87 kW (1.51)
-7°C5.50 kW (2.65)4.78 kW (2.10)4.48 kW (1.70)
2°C5.00 kW (2.97)5.00 kW (2.47)4.48 kW (1.70)
7°C5.50 kW (4.42)5.50 kW (3.32)5.50 kW (2.22)

Alezio Compact 8 MR EM

Air / Water35°C (Power / COP)45°C (Power / COP) 55°C (Power / COP)
-10°C7.69 kW (2.35)7.33 kW (1.88)6.29kW (1.56)
-7°C8.42 kW (2.77)7.99 kW (2.13)7.00 kW (1.74)
2°C7.50 kW (3.40)7.50 kW (2.83)7.14 kW (1.91)
7°C8.00 kW (4.40)8.00 kW (3.40) 8.00 kW (2.77)

Alezio Compact 11 MR EM

Air / Water35°C (Power / COP)45°C (Power / COP) 55°C (Power / COP)
-10°C9.53 kW (2.50)9.36 kW (1.98)8.90kW (1.52)
-7°C10.59 kW (2.73)10.30 kW (2.14)9.69kW (1.62)
2°C10.00 kW (3.32)10.00 kW (2.66) 10.00 kW (1.89)
7°C11.20kW (4.45)11.20kW (3.42) 11.20kW (2.60)

Alezio Compact 16 MR EM

Air / Water35°C (Power / COP)45°C (Power / COP) 55°C (Power / COP)
-10°C11.13 kW (2.43)11.07 kW (1.94)10.57kW (1.51)
-7°C12.37 kW (2.65)12.18 kW (2.10)11.52kW (1.66)
2°C12.00 kW (3.24)12.00 kW (2.52) 12.00 kW (1.86)
7°C16.00kW (4.10)16.00kW (3.23) 15.21kW (2.52)

In our climate, in the North West of Europe, the average annual temperature often oscillates between 2°C and 7°C. You will therefore have an average COP of between 3.20 and 4.40, depending on the power of your machine, if you heat via a hydraulic floor. In the case of radiators that require higher temperatures (45 or 55°C), we can consider that the COP varies between 2.50 and 3.50.

To find the official average COP value over the year, you can refer to the data indicated SCOP in the data sheet linked below.

This means that the energy savings in the case of underfloor heating should be around 70% of your old electricity bill if you were on electric heat. In the case of radiators, the energy savings would be around 50% of your old bill.

We notice low COP when it is -10°C and we ask for 55°C. Approximately 1.5, which means that we are not far from the purely electric heating:

A heat pump absorbs less electricity to operate at low water outlet temperatures

The number of days per year when the heating water temperature demand is maximum (55°C) remains limited, which will not greatly impact your final electricity consumption, and will be very quickly compensated in the milder season with COP of more than 3 or 4.

Not all heat pump manufacturers have the courage to display the performance data up to 55°C or even 60°C so clearly on their official documentation, with COPs that fall below two. De Dietrich is factual and does not try to hide or sell dreams. We feel that we are dealing with rigorous technicians at this manufacturer: Ach is the Alsatian rigor!

The Alezio S Compact machine can also cool, and provides, depending on the size of the machine, a power between 6.80 and 17.00 kW in cooling to deliver water at 18°C with a COP between 3.50 and 4.00

You can find all the data with more details on page 5 and 6 of the technical documentation.

See the technical documentation of Alezio S Compact from Dietrich

Hot water tank

Enameled in food grade and protected by a magnesium anode, it holds 177 liters of water, which is good for about 4 people.


The noise level of the indoor module is very low: between 28dBA and 32dBA. You won't hear it and fortunately it's in a closet!

For the outdoor module which will be in your garden: the announced sound levels correspond to a measurement in free field at 5m. This is equivalent to considering the outdoor module "levitating" and taking the measurement at a distance of 5m from it.

Under these conditions, the noise levels do not exceed 47dBA even for the largest powers.

Alezio Compact4.5681116
Noise level indoor module (free field, at 1m) in dBA2828283232
Noise level outdoor module (free field, at 5m) in dBA3643454747

This free field acoustic measurement rarely corresponds to reality. It is more common for your outdoor module to be installed either on a flat surface in the garden with no walls around it, or along a wall. In both cases there is more reverberation than in the ideal case of free field. This will increase the sound level.

Ask your installer for an acoustical study, without necessarily asking for a great doctoral thesis in acoustics. Alternatively, you can ask an acoustics expert for advice on whether your purchase will comply with public health codes depending on where you want to install it.


In terms of price, the Alezio compact, indoor module + storage tank + outdoor module, is between 7'000€ and 12'000€ TTC depending on the size you choose, and the terms of your heat pump installation company.

To which you will have to add the installation by your heating installer, and a possible maintenance contract every year or two.
The prices of the de Dietrich Alezio Compact are not necessarily highlighted on the website of de Dietrich thermal, however one of their partner ChappéeThe BDR Thermea Group's Eria-N fit-in, which is the same machine, has a recommended retail price before tax.

In general the installation costs about 5'000€ to 7'000€.


Where to get this model of Dietrich heat pump? The best way to get the best price is to ask for a quote from several installers and tell them that you want this one. Indeed, they will not necessarily automatically offer you this heat pump because they have their preferred model. Many work with the Daikin Altherma for example.

Buying the heat pump on your own, and then looking for an installer to carry out the installation, is a step that is generally rather badly perceived. In fact, the installer also earns a living by making a small commercial margin on the device. Furthermore, it is complicated to buy a heat pump from a supplier without him offering to install the equipment, but it does exist.


The regulation will allow to adapt the heating power delivered by the heat pump, according to the actual need of your house in relation to the outside temperature. It manages the compressor and, if there is one, the emergency electric resistance, as well as the domestic hot water.

You also have the possibility of having classic thermostats, or a Smart TC° connected thermostat. The latter allows you to :

  • Controlling temperatures remotely
  • Manage a remote time schedule
  • Access the machine parameters remotely (consumption monitoring)

It works on wifi, and you can connect via an app available on Google Play or Apple Store. Here is what it looks like on iPhone for example:

You can download the apps here to see what it looks like, even if you don't have CAP yet. There is a demo mode.


In terms of space, the Alezio Compact S is designed to be COMPACT 🙂

The hydraulic module is 400mm wide, 712mm high, and 410 deep.

It is grafted onto the 177 liter hot water tank, which is 551 wide. The total of the two, tank + module, is about 2.20m.

dimensions of the Alezio de Dietrich compact S interior module

So you can place the Alezio Compact S of Dietrich in a cupboard or along a wall of technical room, as you wish. But you must leave some space around it to access it if needed.

Alezio S compact de Dietrich in cupboard

Concerning the external group, it depends on the power of the machine, from size 4.5 to size 16.

We notice the group of size 6 is the lowest with 630mm height, 871mm width, and 360mm depth. See here the dimensions for all sizes.

If you are installing the unit along a wall or in a recess, remember that you will need to leave some space around the machine to allow it to breathe. As a standard, always leave 10cm behind the machine, and at least 50cm in front of the machine. The Dietrich doc is very says on this point and considers all possible cases. Here is a small extract

Extract from Dietrich Alezio S Compact


Finally, it is interesting to note that a detailed video of the assembly of this heat pump is visible on Youtube, in 3D. Really well done, we see that at de Dietrich Thermique it masters CAD 🙂


The first impression I mentioned at the top of the article, the Deutsche Qualität: it is confirmed, although the brand is not German but French.

The documentation of these devices is precise and synthetic, very well thought out.

Moreover, de Dietrich does not sell you a dream with out of the ordinary COPs, but stays true by presenting all the temperature data of the machines, even at the highest water temperatures and the lowest outdoor temperatures, when the COPs are bad. Where other brands tend to hide it more.

In terms of performance, it has everything needed to equip all types of homes, with excellent COPs at low temperatures.

Acoustic level, the measurements indicated are very theoretical, and it would be necessary to see the real measurement in a case a little more real than in free field at 5m. But we have not yet heard any case of lawsuit for too much noise from a Dietrich heat pump.

You are dealing here with a two hundred year old industrial empire that inspires confidence, and that offers machines at very competitive prices in the same range as the Daikin Altherma and other Aquarea TCAP or Hitachi Yutaki.

All you have to do is find a heat pump installer who wants to work with this brand.

Read also:

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