Purchasing a heat pump – more efficiency, lower costs

Air heat pumps are among the most widely installed heat pumps in Germany. This is due both to their simple and rapid installation and to their relatively low investment costs. A conventional air source heat pump extracts heat from the outdoor air and raises it to the required temperature through the refrigerant circuit process. Depending on the model, appliances can be installed either outdoors or indoors. In the case of monoblock appliances installed outdoors, the refrigerant circuit is completely built into the heat pump. The generated heating energy is transported into the building with heating water. With split heat pumps, the refrigerant circuit is separated. The heat is transported by refrigerant line to the interior of the building, where the evaporator heat exchanger is located. This guarantees that the outdoor unit is frost-free, even in the event of a power failure.

A special form of air source heat pump is known as an extract air heat pump. Instead of outdoor air, this heat pump uses the extract air from rooms, which tends to be much warmer. This means that the compressor has less work to do to reach the required temperatures. The air volume is usually limited, however, which means that mono mode operation is not possible. As a rule, these types of heat pump are used for very small heat loads.

When compared to the outdoor air, geothermal heat is relatively high below a certain depth. In addition, it remains constant in winter, even when the upper layer of soil is already frozen. Brine/water heat pumps work very efficiently and achieve a COP of up to 5.0. There are two basic methods to choose from when it comes to extracting geothermal heat. If space is limited, geothermal probes are the best option. These are sunk into the earth vertically or at an angle through boreholes and extract heat from the ground at a depth of 40 to 100  metres.

As an alternative to geothermal probes, geothermal collectors only need a shallow depth of around one to two metres, i.e. below the frost line. On the other hand, they require significantly more space due to their horizontal and large-area installation. You can learn in detail about how the heat is recovered in the section entitled How a brine/water heat pump works.

Groundwater is also an excellent heat source, providing consistently high temperatures all year round. Two wells are required for heat recovery. For the water/water heat pump to work efficiently, the groundwater composition and the water volume must meet minimum requirements.

A few years ago, heating with electricity was still considered uneconomical and unecological because efficiency losses were very high and electricity was mainly produced from coal. Since then, however, most heat pumps have become highly efficient and keep heating costs at a permanently low level. One of the main reasons for this is environmental energy as a heat source. Unlike natural gas and oil, environmental energy is not subject to economic or political fluctuations. Most importantly, it is always available and free of charge.

Further economic benefits of a heat pump are its low maintenance operation and the attractive subsidies available from the state. The section on heat pump subsidies explains how to apply for these.

Another point in favour of purchasing a heat pump is the high level of operational reliability and the possibility of obtaining low cost heat pump electricity. What's more, most Viessmann heat pumps are able to lower the temperature in the warmer months of the year using the active and passive cooling function. Other economic benefits of a heat pump are:

• No costs for a chimney and flue gas inspector
  
• Increase in property value when selling
• Meets all EnEV requirements for new build and renovated older buildings

Efficiency plays a very important role in the purchase of a heating system. With increasing environmental awareness, however, climate protection is also coming more and more to the fore. If you invest in a heat pump today, you are also making a major contribution to reducing the harmful greenhouse gas CO₂.

Heat pumps uses renewable energy for heating and require only a small amount of electrical energy, which means less need for the mining and combustion of fossil fuels. The CO₂ balance of the electricity used for heating is significantly lower when compared to other fossil heating systems. If green drive power is also added in, a heat pump can operate entirely carbon free.

Statistics also illustrate how the environmental benefits of a heat pump stack up in practice: according to the German Federal Ministry for Economic Affairs and Energy, the use of renewable energy sources in the heating market alone prevented around 37  million tonnes of CO₂ across Germany in 2016. By way of comparison, energy-related emissions in the transport sector amounted to 166.2 million tonnes in the same year.

Aside from the lower investment costs when compared to other heat pumps, air source heat pumps have further benefits. Retrofitting is possible at any time, without having to obtain official approval. Furthermore, an air source heat pump has a very small footprint, making it suitable for both new build and modernisation projects.

If the option of operating a brine/water heat pump is available, homeowners should give serious consideration to purchasing one. Because of their constantly high output temperatures throughout the year, these heat pumps work very efficiently.  

In essence, heat can be extracted from the ground in two ways –– if space is limited, geothermal probes that are sunk deep into the ground are suitable. If, on the other hand, the house to be heated has a sufficiently large garden that is not built on, geothermal collectors offer a sensible alternative. Similar to underfloor heating, these are laid underneath the top layer of soil. From there, they extract heat from the layer of earth and transfer it to the evaporator. In addition to surface collectors, trench collectors are also an option. These require significantly less space.

The "energy transition" is a project launched by the German government with the aim of meeting Germany's energy needs almost exclusively with renewable energies by 2050. Many experts believe that one strategy that can achieve this goal is to combine the electricity and heating markets, as well as transport, also known as sector coupling. In the electricity and heating markets in particular, heat pumps are an important instrument because:

• Electricity is becoming cleaner due to the expansion of green power plants
• Surplus power from wind turbines and photovoltaic systems must be used sensibly (power to heat)
• Current heat pumps operate highly efficiently and can help to relieve public grids

With an increasing share of green electricity in the energy mix, as well as high efficiency, heat pumps work in a more climate-friendly way than heating technologies based on the combustion of fuels. They also ensure a sustainable, renewable heat supply all year round –– and in large quantities. In theory, they can help to harness surplus power from wind turbines and photovoltaic systems, thus ensuring grid stability. For many experts, this all makes the heat pump the perfect technology for sector coupling.

However, there are still some obstacles in the way of implementation. Firstly, the legal framework conditions needed to give operators sufficient legal certainty of favourable energy prices are not in place. Secondly, electricity is still burdened with high taxes and levies. Politicians are being called upon to change the law accordingly as soon as possible. Still, when surveyed, HVAC installers remain optimistic that demand for heat pumps will increase significantly in the coming years.