Kermi x-buffer heat storage

x-buffer® heat storage Versions

General information

Generating heat is one thing, storing heat with as little loss as possible is another. Because the total amount of energy generated by the heat pump is not always completely used immediately.

This is where the x-buffer buffer and domestic hot water storage come into play. Regardless of whether it is a matter of comfortable heating warmth or hygienically perfect domestic water: heat storage is an important element in a future-oriented heating system.

The The buffer storage ensures that the heat source and the heat consumption are decoupled. This means that heat can be generated independently of the time of consumption. This means that your heat pump does not have to start up again every time you turn up a radiator. The effect is similar to the one you are familiar with from the car: if you drive at an even pace without continuously accelerating and braking, your journey is considerably more environmentally friendly (and cheaper).

The buffer storage is used to bridge cut-off times or peak loads. It ensures that after a long day at work, you quickly feel comfortably warm and do not have to wait for heat to be generated.

Domestic hot water storage ensures that there is always enough hot water available, even if everyone wants a bath. Just like the buffer storage, generation and consumption are decoupled here as well.

Combined storage combines buffer and domestic hot water storage in one unit. The two different types are storage are, however, strictly separated from one another. Combined storage is often the optimal solution if there is little space in the cellar but you would still like to have an efficient and environmentally-friendly storage system.

Kermi x-buffer combi buffer and domestic hot water storage

x-buffer combi buffer and domestic hot water storage

The new x-buffer combi contains every important component for connecting an x-change heat pump to the heating system and for domestic water heating. The attractive and timeless design will fit into every furnace room, engineering or utility room. All the hydraulic and electrical components required to operate a heat pump system are integrated. A 204 litre (nominal volume) enamelled storage tank with an integrated heating rod and a circulation connection is available for domestic water heating. The respective heating system is supplied with heat via the heating buffer storage tank with a volume of 127 litres with an integrated heating rod and connected, unmixed heating circuit. At the same time, the volume flow of the heat pump is hydraulically isolated from the heating system. This allows the heat pump to work with much greater efficiency and only the volume flow actually required is circulating in the heating system. An additional mixed heating circuit can be installed as an option, thus increasing the possible uses of the x-buffer combi. The buffer charging pump and the switchover valve are integrated. Thanks to cleverly positioned carrying handles and its compact design, it is not a problem to transport it into the respective building. The innovative and flexible line routing for the heating circuit and charging the storage tank makes for short line routes in tight spaces. This system solution simplifies the overall installation of the heat pump, saves space and time during installation, and in this way reduces the overall investment costs.



  • Buffer storage tank 127 litres
  • Domestic water storage tank 204 litres (useable) with an internal 3.5 m² large heat exchanger optimised for heat pumps
  • Integrated three-way changeover valve for heating/domestic water with storage charging pump
  • Integrated electric heating rods in both storage tanks
  • Circulation connection provided
  • Circulation pump integrated for unmixed heating circuit
  • All electrical components are wired in advance
  • Extremely easy and time-saving installation of the whole system
  • All maintenance carried out from the front
  • Extremely good storage insulation
  • High quality, powder-coated sheet metal cladding all the way around
Kermi x-buffer combi buffer and domestic hot water storage

x-buffer flex layered buffer storage tank

Available from November 15th, 2020

The x-buffer® flex stores the heat energy generated by the x-change heat pump and delivers it to the heating system and hot water. Innovative and energy-efficient thanks to our tried and trusted layer optimisation system combined with the Neodul insulation, practical thanks to the small tilted dimension and the flexible individual configuration of the pump groups mounted at the front.The buffer and hot water storage tank are convincing with their modern design as well as by allowing quick and self-explanatory, flawless installation of the hydraulic tower.

  • Space-saving combination solutions for heating warmth and hot water
  • Clear design, quick and easy installation
  • All electrical components are completely wired in advance
  • Flexible cable layout on site
  • Ideal for operating with heat pumps
  • Flexible setup on wall possible on left or right
  • All pipes supplied between storage tank & hydraulic tower can be installed quickly sealing flat.
  • Connections are available for additional heat sources, solar integration and accessories.
  • Maintenance only from the front


  • Storage capacity of 620 to 1300 litres
  • Attractive design with high quality surface of insulation and beautifully shaped EPP cover over the hydraulic tower.
  • Space-saving storage tank with large storage capacity, perfectly suited for Power-to-Heat for example
  • Storage tank perfectly suited for operation with heat pumps, combined with tried and trusted layering principle using the integrated inflow damper, ensure maximum energy efficiency
  • Flexible space-saving setup possible (on wall, left or right)
  • Hygienic and powerful domestic water heating thanks to the integrated, electronic fresh water station
  • Lower heat losses thanks to high quality Neodul storage tank insulation
  • Hybrid storage solutions to incorporate additional heat sources, such as solar panels (including retrospective fitting)
Kermi x-buffer flex Schichtenspeicher

x-buffer compact buffer storage

The x-buffer compact buffer storage tank stores the heat energy generated and delivers it to the heating system. Thanks to modern fleece insulation, this innovative storage unit keeps heat losses extremely small.



  • Four different buffer sizes
  • Low operational losses thanks to high quality all-round insulation
  • Fleece insulation with polystyrene cladding
  • Building material class B2 according to DIN 4102
  • Versatile and flexible use, with appropriate arrangement of the connections


Kermi x-buffer compact buffer storage

x-buffer compact cool buffer storage

The x-buffer compact cool buffer storage can be used for heating and cooling modes with heat pumps. The buffer storage is used to hydraulically isolate the volume flows, extend the service life of the heat pump, and store heat energy. The high quality polyurethane rigid foam insulation with an external PVC coating reduces the heat losses to a minimum.


Consisting of:

  • Buffer storage tank directly foam-coated with PU rigid foam insulation
  • Building material class B2 according to DIN 4102
Kermi x-buffer compact cool buffer storage

x-buffer fresh domestic hot water storage

The x-buffer fresh hot water storage tank is a high-performance storage tank for domestic water heating in conjunction with a heat pump. The PU thermal insulation assures minimal heat losses.



  • Available in two sizes
  • 50 mm PU rigid-foam insulation with PVC cladding
  • Storage with glass enamelling according to DIN 4753
  • Integrated magnesium sacrificial anode
  • Flange opening
  • Heat exchanger for heat pump applications


Kermi x-buffer fresh hot water storage

Video instructions

The special layering process guarantees optimal layering of layers of water at different temperatures in the Kermi x-buffer layered buffer storage tank.

Mixing volumes of cold and warm water is virtually impossible with this process which has a patent pending. The water which slowly flows into the storage tank can rise or sink, depending on the temperature. Together with high quality all-round insulation, this significantly minimises energy losses.

The innovative housing design of the x-buffer layered buffer storage tank makes the storage unit a space-saving alternative.

The system does not take up any more room than a conventional heating tank. Thanks to a special floor construction, the tilt dimension (diagonal) is scarcely any greater that the setup dimensions. This means that from the outside as well, the x-buffer layered buffer storage is also different from conventional storage models and is highly suitable for rooms with low ceilings in existing buildings. With the intelligent arrangement of the connections, the x-buffer also fits through narrow doors.

5 year system warranty

Finally the new Kermi heating system has been installed. Or the Kermi ventilation system. Nothing left to stop you feeling cosy at home. With our 5-year system warranty, we are happy to prove the quality of our products and our service promise to you.

Just three steps to a 5 year system warranty:

1. Have the Kermi system installed by a specialist company
2. Have Kermi Customer Service commission the system (or in the case of ventilation systems, a specialist company)
3. Annual servicing by Kermi Customer Service or by a specialist company

Kermi: Clear advantages. Complete service.

Comprehensive Kermi system x-optimised

  • Energy savings up to 34 %
  • Optimally matched components
  • Everything from a single source, from planning to commissioning

This means "Kermi system x-optimised"

12 good reasons for Kermi system x-optimised

Kermi - Zertifizierte Qualität

Certified quality

  • Kermi is certified according to DIN EN ISO 9001;2008, 14001:2004 and 50001:2011
  • Components comply with current standards and directives
  • Regular monitoring of core components by independent testing institutes
Kermi download technical data sets

Support with order process and planning

  • Support with order preparation
  • Support with a wide range of services during system planning
  • Dimensioning data set for liNear software
  • Comprehensive software for dimensioning rooms
  • Comprehensive information material
  • Extensive technical Internet portal
Kermi x-net C11: with outstanding customer service

Complete customer service

  • Nationwide service team as well as field service teams for fast on-site assistance
  • Competent in-house service team for fast telephone assistance
  • Professional, unbureaucratic processing of complaints
  • Detailed initial training on-site
  • Detailed planning and design consultation
Kermi system knowledge down to the last detail

System knowledge in great detail

  • Carefully engineered system technology developed in-house for easier, fast, safe work
  • Many Kermi innovations
  • Kermi special solutions for practical application by tradespeople

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