The combination of heat pumps and gas condensing boilers in hybrid systems offers pioneering solutions for energy-efficient and flexible heating systems in residential buildings, large housing estates, and public and commercial buildings. Hybrid heating systems offer an optimum combination of renewable energy and proven gas heating technology, particularly for modernisation projects but also for new builds. The systems adapt flexibly to different load profiles and guarantee a reliable heat supply – from apartment blocks, hotels and sports facilities to administrative and educational establishments. 

The principle of hybrid solutions is based on intelligent control of the heat generators: the heat pump takes over the base load and utilises environmental energy from the air, ground or water, while the gas boiler steps in at peak loads or very cold outdoor temperatures. This reduces gas consumption and cuts CO₂ emissions – an important contribution to climate change mitigation. 

In this article, we explain the technical principles, mode of function, and advantages of hybrid systems. 

A hybrid system consists of at least two heat generators that work together intelligently depending on the outdoor temperature and heating load. The heat pump, for example an air/water heat pump, utilises environmental heat to generate thermal energy with low power consumption. As a rule, it covers the base load of the heating system – i.e. the majority of the heat requirement – and works particularly efficiently at moderate outdoor temperatures. 

The gas condensing boiler supplements the heat pump during peak demand or very cold outdoor temperatures when the efficiency of the air/water heat pump drops. This combination ensures a reliable heat supply and at the same time significantly reduces fossil fuel consumption. 

A central control unit (also known as a hybrid manager or system controller), such as TopTronic E from Hoval, continuously monitors the outdoor temperature, heating load and system statuses. It decides in real time which heat generator currently provides the most efficient operation and switches accordingly. 

• The heat pump is the centrepiece of the hybrid system. It extracts heat from the environment and raises it to a temperature level suitable for heating and domestic hot water by means of a refrigeration circuit. Air/water heat pumps are particularly flexible and easy to install, whereas brine/water or water/water heat pumps offer higher efficiency at more constant temperatures, because they operate independently of the outdoor temperature. 

The Hoval Belaria heat pump, specially developed for hybrid operation, is characterised by its high coefficient of performance (COP), quiet operation and compact design. The heat pump is designed to work optimally with a gas condensing boiler and reliably cover the base load. 

• The gas condensing boiler takes over at peak load times when the heat pump is no longer operating economically – for example, when outdoor temperatures are very low or when there is a high demand for heat. Modern condensing boilers such as the UltraGas 2 from Hoval have a modulated output that adapts continuously to the actual demand. This reduces frequent switching on and off, increases service life and improves energy efficiency. 

• The intelligent control system ensures automated and efficient operation of the hybrid heating system. It defines a bivalence point, by which is meant the outdoor temperature at which the heat pump still works efficiently. At outdoor temperatures above this temperature, the heat pump operates as the sole heat generator. If it falls below this level, the control system automatically switches to the gas condensing boiler. The TopTronic E modular system control monitors all relevant parameters such as outdoor temperature, heat load, hot water demand and system statuses. It also ensures a seamless transition between heat generators, optimises energy consumption and enables simple operation, including via remote maintenance. 

• Hydronic integration and buffer storage tank: The hydronic integration of heat pump, condensing boiler and heating circuit(s) guarantees a demand-orientated heat flow. A connected buffer storage tank temporarily stores excess thermal energy from the heat pump, stabilises its operation and balances out load peaks. This measurably increases system efficiency and heating comfort. 

Hydronic balancing ensures that each heating surface receives exactly the amount of heating water required to achieve the desired room temperature. Without this balancing, uneven heat distribution, increased energy consumption and loss of comfort can occur. Hydronic balancing is essential, particularly in hybrid systems with heat pumps and gas boilers, in order to fully utilise the efficiency potential of both heat generators and ensure trouble-free, economical operation.

Hydronic balancing ideally equalises different pressure resistances and flow rates in the pipe network, enabling energy savings of up to 15%.

• High energy efficiency: Optimum utilisation of environmental energy and demand-driven activation of the gas boiler reduces energy consumption. 

• Reliable heat supply: A constant and comfortable heat supply is guaranteed even at very cold outdoor temperatures. 

• Flexibility and retrofittability: Existing gas heating systems can be supplemented with a heat pump, making modernisation easier and reducing investment costs. 

• Reduced operating costs and CO₂ emissions: The combination noticeably reduces gas consumption and improves the environmental impact. CO₂ emissions are reduced through the use of renewable energy sources. 

• Convenient operation: The intelligent control system enables automatic operation and simple operation, including remote access. 

• Long service life: Modulating operation and intelligent control minimise wear and maintenance costs. 

Hybrid systems that integrate heat pumps and gas boilers represent an economical and environmentally friendly solution for modern heating systems with scope for future expansion. With its sophisticated systems and intelligent control, Hoval offers optimally harmonised hybrid solutions that offer planners and building owners maximum flexibility, efficiency and convenience.  

Contact our experts for individual advice and customised hybrid heating solutions from Hoval.