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

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 ancestor Jean de Dietrich acquired a forge in a small village in the Vosges du Nord Nature Park: Jaegerthal.

It's a very picturesque place, typical of the small villages of Alsace, in a green setting where you can still visit the ruins of the forge.

One thing led to another, and the family went on to build up an impressive industrial empire, in the field of railway (now sold to Alstom Reichshoffen), in the field of heating and later in industry chemical and pharmaceutical.

If you want a quote for this machine, you can can request it from our network of installers France Switzerland or Belgium through the form below

Jean de Dietrich's son was even the first mayor of Strasbourg after the Revolution, and commissioned Rouget de l'Isle to write the French anthem "La Marseillaise". That's a lot of this family's deep ties to French history!

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 as shown in the photo above. It shows the outdoor unit (for the garden) on the left, and the indoor module on the right, grafted on top of the domestic hot water tank.

It's a model that's very much in evidence in Alsace, of course. 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 speaking, the outdoor unit shown in the photo above is quite compact and the ventilation grille fits well. As for the indoor unit and storage tank, which are connected together, they are designed to be placed in a cupboard, so it doesn't matter how they look.

The idea behind this compact split air/water heat pump is to integrate it into a modern environment, in a kitchen cupboard for example, as you'll 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 wide range of heating capacities means they are equally suited to a small apartment, a low-energy house or a traditional, less well-insulated house with a larger floor area.

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 North-Western European climates, the average annual temperature often fluctuates between 2°C and 7°C. Depending on the power of your machine, your COP will therefore average between 3.20 and 4.40, if you heat via a hydraulic underfloor heating system. In the case of radiators requiring higher temperatures (45 or 55°C), the COP can be considered to vary between 2.50 and 3.50.

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

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

We notice low COP values when it's -10°C and 55°C is required. Around 1.5, which means we're not far from purely electric heating:

A heat pump absorbs less electricity to operate when water outlet temperatures are low.

The number of days a year when heating water temperature demand is at its highest (55°C) remains limited, which won't have a major impact on your final electricity consumption, and will be quickly compensated for in the warmer season with COPs of over 3 or 4.

Not all heat pump manufacturers have the courage to display performance data up to 55°C, or even 60°C, so clearly on their official documentation, with COPs falling below two. De Dietrich is factual and doesn't try to hide or sell dreams. You get the feeling that you're dealing with rigorous technicians at this manufacturer: Ach c'est la rigueur Alsacienne!

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.

View technical documentation for Dietrich Alezio S Compact

Domestic hot water tank

Enamelled in food-grade quality and protected by a magnesium anode, it holds 177 liters of water, which is good for around 4 people.


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

For the outdoor module in your garden: the sound levels quoted correspond to a free-field measurement 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. In fact, it's 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 noise level.

Ask your installer for an acoustic study, without necessarily requiring a doctoral thesis in acoustics. Alternatively, you can ask an acoustics expert for advice on whether your purchase will comply with public health regulations, depending on where you plan to install it.


In terms of price, the Alezio compact, indoor module + storage tank + outdoor module, ranges from 7'000€ and 12'000€ incl. VAT depending on the size you choose, and the conditions of your heat pump installation company.

You'll also need to pay for installation by your heating engineer, and a maintenance contract every year or two.
Prices for the de Dietrich Alezio Compact are not necessarily highlighted on the de Dietrich Thermal website, however one of their partners ChappéeBDR Thermea Group's Eria-N fit-in is the same machine.

Installation generally costs between €5,000 and €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 a heat pump on your own, and then looking for an installer to carry out the installation, is a step that's generally frowned upon. In fact, the installer also earns a living by making a small commercial margin on the unit. It's also complicated to buy a heat pump from a supplier without the latter offering to install the equipment, but it does exist.


The control system adapts the heating power delivered by the heat pump to your home's current needs, in relation to the outside temperature. It manages the compressor and, if fitted, the backup electric resistance, as well as the domestic hot water.

You can also choose between conventional 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's like, even if you don't have CAP yet. There's also 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 cylinder, which is 551 wide. The total of the two, tank + module, is approximately 2.20m.

dimensions of the Alezio de Dietrich compact S interior module

The Dietrich Alezio Compact S can be installed either in a cupboard or along the wall of a technical room. But you still need to leave some space around it for access if necessary.

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're installing the unit along a wall or in a recess, remember that you'll need to leave some space around the machine to allow it to breathe. As a rule, always leave 10cm behind the machine, and at least 50cm in front of it. 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's interesting to note that a detailed video of the assembly of this heat pump can be seen on Youtube, in 3D. Really well done, you can see that de Dietrich Thermique has mastered CAD 🙂


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

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

Furthermore, de Dietrich doesn't sell you a dream with out-of-the-ordinary COPs, but stays true to form by presenting all machine temperature data, even at the highest water temperatures and lowest outdoor temperatures, when COPs are poor. Where other brands tend to hide it.

Performance-wise, it has what it takes to equip all types of homes, with excellent COPs at low temperatures.

In terms of acoustics, the measurements given are very theoretical, and we'd have to see the real thing in a slightly more real case than in a free field at 5m. But we've yet to hear of a case where a Dietrich heat pump was sued for excessive noise.

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.

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

Read also:

Review of Atlantic Alfea Extensa Duo, another French heat pump

Other French heat pumps

All air water heat pump reviews

TOP 20 Best air-to-water heat pumps

About the author

Juliena mechanical engineering graduate and specialist in climate engineering since 2009, has become a writer specializing in renewable energies, with expertise in heat pumps and photovoltaic solar panels for individual housing.