As a rule, buildings and households are supplied with natural gas or heating oil for heat. A modern and efficient alternative to this is local and long-distance heating . The term “central” heat supply is also often used . Contrary to the conventional heat supply with gas or oil, which happens decentrally – i.e. in your own four walls – you are supplied with local or district heating. The energy is produced in combined heat and power plants or heating plants. The hot water is then delivered directly to the consumer via pipe systems. The heating networks usually supply several buildings or streets, sometimes even entire districts, with heat.
The difference between local heating and district heating is actually just a linguistic one. The technology behind both systems is the same. One tends to speak of local heating when it comes to smaller, more decentralized networks. If the networks are larger and reach more households, it is district heating. It is not possible to draw an exact boundary between the two products, but it is not necessary in principle because they work in the same way. From a legal point of view, local heating surprisingly also falls under the term district heating.
Heat is often a simple by-product in this context . When generating other forms of energy – mostly electricity – heat is also generated. These heat losses are used efficiently in local and district heating.
The technology behind it in most plants is called combined heat and power (CHP). In this process, electricity and heat are produced together. The fuels that are used are mainly fossil fuels such as natural gas, hard coal or lignite. These are then used twice: on the one hand for the generation of electricity, but also for heat. This is extremely efficient and resource-saving. Through miles of transmission lines, the hot water heated by this process is then delivered to the buildings and used for space heating and hot water production. Finally, the cycle ends when the water is returned cold and used again.
Other technologies that are also used, albeit less, are combined heat and power plants, waste incineration plants or biomass power plants. In smaller plants, biomass is often used to generate heat. The advantage is the significantly lower CO2 emissions than with conventional district heating. Using waste heat from industry is another way of generating district heating.
District heating is most commonly found in large, densely populated cities. It is used less frequently in rural regions, as it is too expensive to set up a network in such areas and, in relative terms, can cover too few households.
3,000 (of around 12,000) towns and communities in Germany have a district heating supply. According to statistics from the Energy Efficiency Association for Heat, Cooling and KWK e. V. (AGFW) almost 21,000 km – divided into 1,400 independent heating networks.
The district heating sector already supplies around 5 million households with heat and is therefore between 5% and 13.5% of the total supply, depending on the city and federal state. In the largest federal states in terms of area, such as Bavaria, the proportion is rather low due to the relatively rural environment. In the city states and the new federal states, the shares are between 20% and 40%.
Connection to the grid is particularly popular for new buildings. From 7% in 2000, the proportion has risen to 20% within 15 years.
In principle, every heating method has disadvantages, including local and district heating. The bottom line is that there is no reason not to recommend local or district heating: if you want a reliable supply of heat, district heating is definitely a good choice. It is also far ahead of natural gas or oil when it comes to the climate balance. The only obstacle is that the networks have not (yet) been expanded throughout Germany and therefore not all households have the prerequisites for connection to a heating network.
In order to find out whether it is worth converting to district heating, it is not enough just to compare the prices of district heating with oil or natural gas. Because the district heating price already includes conversion losses that arise when the heat is generated. With gas or oil heating, on the other hand, these production losses only occur locally in the heating boiler. So you need more gas or oil to produce the same amount of heat.
Therefore, you should definitely make a so-called full cost comparison. All costs incurred over the period of use of the heating system are taken into account. These include acquisition costs and maintenance.