CHP unit – Heat and power for commercial use

CHP unit for heat and power

The CHP units developed by Viessmann are designed for commercial and municipal use. Correspondingly, they have a high performance and are matched to the operational processes for a secure supply of electricity, heating/cooling as well as domestic hot water. This means that you are not only investing in greater efficiency, but also in the future.  

Compact appliances from the Vitobloc  200 product range are designed as decentralised CHP units with a bias towards heating. These comparatively small units generate electricity for self-consumption. The heat that is generated by this process is used simultaneously, almost without losses, for heating. Any power not required is exported to the public grid and the power supply utility provides remuneration accordingly.

Why a combined heat and power unit (CHP)?

The majority of power generated in Germany is produced in condensation power stations. This means that heating energy is converted into electrical power via a steam turbine. The average efficiency of all conventional power stations is approximately 38 percent, which means that over 60 percent of the energy input is lost to the environment as unused waste heat.

A combined heat and power unit goes one step further here and uses the waste heat, which can increase the overall efficiency of the system. In the case of large-scale CHP systems, this is done via district heating pipelines. However, the potential is largely exhausted in the existing stock. Ultimately, it only works if there are also large heat consumers, such as a housing estate, near the power station.

This is where the idea of decentralised combined heat and power units (CHP) with a heating bias comes into its own. Power is generated in comparatively small units where the heat by-product does not have to be transported over long distances simultaneously (which would incur heat loss), but can be used directly on site. There are also no losses arising from power distribution.

Decentralised power supply with combined heat and power unit

Central power stations usually only produce electricity. The accumulating heat is lost. In contrast, combined heat and power (CHP) uses up to 36  percent less primary energy –– which means a significant reduction in energy costs.

Structure and function of a CHP unit

A CHP unit essentially consists of an engine, a synchronous generator and a heat exchanger. The synchronous generator, driven by the internal combustion engine (drive unit), generates a 3-phase alternating current with a frequency of 50  Hz and a voltage of 400  volts, which is generally used on site.

The low voltage grid (0.4  kV level) is used for the electrical connection. As a rule, CHP units are operated in parallel to the mains. In principle, however, they can also be used in mains substitution mode by deploying synchronous generators. Surplus power can be exported to the power supply utility's grid.

The engine generates heat that can be absorbed in the "internal cooling circuit" successively from the lubricating oil, the engine coolant and the exhaust gas, and transferred to the heating system via a plate heat exchanger.

This system of energy generation and utilisation is referred to as combined heat and power (CHP) generation because the mechanical energy (power) generated by the engine and the thermal energy (heat) given off by the engine as it drives the generator are both used simultaneously.

In a combined heat and power unit, a gas-powered combustion engine drives a generator to produce electricity. The heat this creates is extracted from the coolant and exhaust gas via the heat exchanger and can then be utilised.

In order to make the use of a CHP unit economically viable, the appliance should run continuously for as long as possible. The longer a CHP unit can realistically transfer heat and power into a system, the sooner it will pay for itself. When it comes to sizing, apart from some exceptions (such as emergency power supply) the focus is on heat. The CHP unit is heat-led.

Permanent annual curve –– design of the output of a CHP unit  

If we look at how the annual heating output typically is spread over a 12  month period (permanent annual line), it becomes clear that a CHP unit should not be oversized. Its thermal output is calculated in such a way that heat can still be transferred even at times of low load.

In order to achieve a runtime of at least 4500  hours, we can assume approximately 20  percent of the boiler output as thermal output of the CHP unit to provide heating for the building.

On the heating side, the CHP unit operates in parallel with a boiler. Both heat generators are connected to the heating system, the DHW heating or other heat consumers, such as a swimming pool.

Depending on the consumption profile of the building, it may make sense to use a heating water buffer cylinder so that the runtime of the CHP module can be as long and uninterrupted as possible.

On the power side, the first priority is to cover the building's self-consumption. If no more consumers are available, the electricity is fed into the public grid and remunerated.


Power: for self-consumption or for exporting to the grid

Electricity for use on site is generated in units tailored to the respective requirement. Any power not required is exported to the public grid and the power supply utility provides remuneration accordingly.


Heat: use efficiently and almost loss-free

However, the heat generated in a combined heat and power unit is not lost, unlike with central power stations. The heat is fed into the heating network. Together with another heat generator, such as a boiler, the building is supplied with power, heat and DHW almost loss-free. Also, the cooling demand can be completely or partially covered by coupling with an absorption cooling machine.

The picture shows the schematic of a system integration for a CHP unit
Display of a Vitobloc 300 type NG

Since a CHP unit essentially pays for itself by reducing the amount of power drawn from the grid (and not through the feed-in remuneration), the consumption of electrical energy in the building must also be taken into account. By answering three simple questions, you can quickly check whether it makes sense to use a Vitobloc CHP unit:

  • Is the required boiler output above 60  kW or the gas consumption in excess of 90000  kWh/a (relative to the gross calorific value)?
  • Is the annual power consumption in excess of 32000  kWh?
  • Are heat and power consumed simultaneously?

If the answer to all of these questions is "yes" and a gas connection is available, it is worth looking more closely into using a CHP unit.

Vitobloc 200 and 300 – compact, quiet and supplied ready-to-connect

Vitobloc 300 NG 15 and Vitobloc 300 NG 20 are compact, ready-to-connect units with water-cooled synchronous generators for producing three-phase power and heating water. With their low operating noise and small space requirement, they are suitable for new build and modernisation projects alike.

The Vitobloc 300 CHP units are suitable for natural gas, bio natural gas, LPG and the admixture of 20 percent hydrogen. The integrated condensing technology enables you to achieve an overall efficiency of up to 107.3 percent (Vitobloc 300 type NG 20).

The Vitobloc 200 series

CHP units such as the Vitobloc 200 type EM-260/390 or the Vitobloc 200 type EM-100/167 from Viessmann achieve impressive efficiency. The Vitobloc 200 CHP units are therefore particularly easy to maintain with their maintenance intervals. Some have integrated condensing technology and thus achieve an overall efficiency of up to 95 percent. And they are up to 50 percent electrically modulated and can be run with both heat-led and power-led operation. Other plus points for the Vitobloc 200 CHP unit are the extensive technical equipment with electricity meter and flexible connections for gas, flue gas, extract air and heating water, as well as the standard silencer hood for significantly reduced operating noise.

Benefits and advantages




Very high electrical efficiencies due to energy efficiency engines and synchronous generators

Maximum economic efficiency through the highest possible proportion of electricity generated


Equipped as standard with starter batteries and synchronous generator

Suitable for mains substitution mode, idle current demand is not increased, correction system and switch-on resistors for asynchronous operation are not required


4-pole feed-in switch (3-pole up to 20  kWel), initial filling of lubricating oil tank, flexible connections, calibrated electricity meter, heating water return temperature raising facility, preservation for 24  weeks, heat modulation mode for DN and LE

Reduces the follow-up costs for system integration


Integration of gas line, starter batteries, lubricating oil supply, control panel in the unit

Silencer hood and extract fan up to 150  kWel

Time and cost savings during engineering, installation, commissioning and operation


Autonomous operation following heat modulation for single unit systems

Eliminates costs for control integration


Certified safety technology in line with Appliances Directive 90/396/EEC with product identification number in series production

Insurance cover and operational reliability are proven


Factory test run of the complete module with engine, generator, heat exchangers and control panel under full load

Minimal commissioning effort, verified performance data


Safety through design, assembly and acceptance in a manufacturing plant certified in line with ISO 9001/EN 29001

Advanced technology already used in approx. 600 successfully installed CHP units


Exclusive use of qualified components from renowned brand manufacturers

Highest operational reliability and long term guaranteed spare parts procurement, high value retention


Update on relief from the Renewable Energy Sources Act levy for CHP systems

The Energy Collection Act came into force on 01/01/2019. It contains amendments to the Renewable Energy Sources Act and the German CHP Act. The former is primarily about reducing the Renewable Energy Sources Act levy for highly efficient newer CHP systems. The following points should be considered here:

  1. New CHP systems and CHP systems that have gone into operation since 1  August  2014 and have an electrical output of less than one or more than ten megawatts will continue to pay only 40  percent of the Renewable Energy Sources Act levy.
  2. All new CHP systems in companies with high electricity costs will continue to pay only 40  percent of the Renewable Energy Sources Act levy.
  3. For the remaining new CHP systems, the privilege of a 40  percent Renewable Energy Sources Act levy only exists if the CHP system runs less than 3500 full utilisation hours per year. For CHP systems with higher utilisation, the average levy increases continuously and reaches the value of a full Renewable Energy Sources Act levy at 7000 full utilisation hours.
  4. For new CHP installations built between 1  August  2014 and 31  December  2018 and falling under item three of this list, a graduated transitional arrangement applies until 2019 or  2020.
  5. The compromise applies retroactively to 1  January  2018. Accordingly, parts of the 100  percent Renewable Energy Sources Act levy paid flow back to the CHP system operators.

The amendments to the CHP  Act relate, among other things, aspects of promotion. For example, this was extended to 2025 for new installations, whereas the subsidy for existing installations was reduced. In addition, there is now a culmination exclusion. Further subsidies in addition to the support via the CHP Act are not permissible.  

The right partner for your CHP unit: Viessmann

Viessmann Kraft-Wäärme-Kopplung GmbH (formerly ESS –– Energie Systeme & Service GmbH) is the Viessmann Group's CHP specialist and has been a member of the Group since 2008. With more than 25 years' experience in this product area, Viessmann offers efficient gas operated systems for combined heat and power generation. Alongside standard products, the company also manufactures CHP units tailored specifically to customers' individual needs.

CHP units – efficient gas-operated systems for combined heat and power generation

Gas-operated combined heat and power units (CHP) generate electrical energy and heat simultaneously according to the principle of combined heat and power. A special gas combustion engine designed for heavy duty cycles drives the generator to produce electricity. These units are sized to suit residential complexes and commercial operations. On the heating side, the CHP unit operates in parallel with a boiler. Both heat generators are connected to the heating system in order to provide heating water or DHW.

Viessmann CHP units are team players. They achieve their highest efficiency in a system that is individually matched to the respective requirements. This starts with system technology, for example, with control cabinets for higher level control functions, and extends to customised maintenance contracts.

Product range: CHP units up to 530 kWel and 660 kWth

A CHP unit is extremely environmentally responsible: in addition to primary energy savings of up to 36 percent, CO₂ emissions are significantly lower compared to the conventional generation of power and heat. With more than 25 years' experience in this product area, Viessmann offers efficient gas operated systems for combined heat and power generation. Alongside standard products, the company also manufactures CHP units tailored specifically to customers' individual needs.

Current documents, forms and brochures to download

You can obtain technical datasheets on the CHP units here. Further forms are available on request. Talk to your Viessmann field staff representative.

Datasheets/specification (PDF)

Datasheets for all Vitobloc CHP units are available for download in our ViBooks database.

Launch ViBooks

Unit certificate

Type-specific certificates for each power-generating unit to demonstrate the conformity of a planned power-generating system with the requirements of these VDE Application Rules.

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