Efficient heating with district heating

District heating grids transport thermal energy from central heat generation plants to consumers in the surrounding area. In densely populated areas in particular, they supply heat to individual buildings, but also to neighbourhoods and entire districts. The use of industrial waste heat and the option of increasingly using renewable energies for heat generation makes district heating an important lever in the energy transition. But what exactly is district heating, what cost points should be anticipated and what advantages and disadvantages should district heating customers be aware of? Find out more in the following guide.

District heating replaces own heating

District heating is produced in different ways. In most cases, however, it is a waste product of other processes. This way, waste heat can be used efficiently, such as in waste incineration plants or in the generation of electricity with large combined heat and power units (CHP). This thermal energy is transported to consumers via district heating pipes running above or below ground. Households that are connected to the heating network do not need their own boiler. In most cases, domestic hot water is also heated by the district heating system. Hot water is predominantly used as the heat transfer medium. It circulates in a closed system and transfers the thermal energy at the district heating transfer station to the local heating system of connected buildings.

The supply of local heat also works according to the same principle, but local heating grids transmit heat over comparatively short distances. In addition, smaller heating centres are usually used. Heat is generated, for example, with larger biomass boilers, medium combined heat and power units, large heat pumps or a combination. Depending on regional conditions, however, industrial waste heat may also be used.

Requirements for a district heating connection

District heating cannot always replace domestic heating. An important prerequisite is that the building is located within the connection area of a district heating provider. These are mainly concentrated in urban areas. After all, for the expense of laying the heating grids to be economically worthwhile, there must be as many consumers as possible. A district heating connection may also be possible in densely populated new development areas or as an additional heat supply for industrial or commercial consumers. As already mentioned, the installation of a heat interface unit is needed for district heating to work. However, the construction work on the building is quite manageable.  

District heating networks enable a more sustainable heat supply

Governments are relying on district heating, among other things, in order to achieve ambitious climate targets. How efficient and sustainable district heating actually is depends on a number of factors. Important factors include:    

• Heat source

• Efficiency of the power plants

• Grid losses

District heating as a valuable by-product

The thermal energy for heat grids is almost always produced as a by-product, for example during waste incineration. Without appropriate use, this energy would remain unused and resources would be wasted. Combined heat and power (CHP) – the combined generation of electricity and heat – also plays an important role in connection with district heating. This is because power plants primarily serve to produce electricity. Through the additional use of the heat generated in the process, it is possible to achieve an energy yield of up to 80  percent. How efficiently the resources are used also depends on the grid losses. In some cases, the thermal energy needs to be transported over long distances to reach consumers. Heat loss can then occur via the pipes.

Share of renewable energies

CHP plants still burn mostly fossil fuels such as gas, lignite and anthracite. However, the thermal energy can also come from renewable sources, such as biomass or geothermal power plants, large solar thermal systems or heat pumps.

Anergy networks combine district heating and heat pumps

In anergy or cold heat networks, heat loss via the pipes is lower. This is because, unlike in traditional district heating grids, the heat transfer medium is not at 80  to 130  degrees Celsius. The water only has a temperature of between ten and 25  degrees Celsius. This makes it suitable for both heating and cooling. Another difference lies in the type of heat transfer. This does not take place at a traditional heat interface unit, but with the help of a heat pump that raises the temperature level as part of a technical process. Probe or well drilling and the requisite permits for the heat pump are not required for cold district heating.

The costs for district heating vary

It is not possible to put a precise figure on how high the costs for district heating will be. In any event, district heating prices or running costs are made up of the following components:

• Base price

• Commodity price

• (service price)

The base price and commodity price determine running costs

Under the base or performance price, district heating providers combine costs for maintenance and care of the heating network, as well as personnel and administration. The price is fixed and depends on the level of the connected load. The following always applies: the more consumers connected to the district heating grid, the lower the base price. This is because the provider can pass on ongoing costs to more customers. The commodity price is used to calculate how much heat is taken from the grid. This therefore depends on individual consumption. In addition, some district heating providers charge for services such as metering and billing as well. Due to the different influencing factors, the price of district heating varies greatly.

Investing in renewable energies pays off

Whether it's a new build or an existing building –– district heating has advantages as well as disadvantages. The advantages include the fact that no boiler, flue system or fuel are required. All costs for purchase and maintenance are thus eliminated. The required heat interface unit also takes up comparatively little space. The use of heat that would otherwise be lost as a waste product is also fundamentally beneficial. If this comes from renewable energies, CO₂ emissions are also reduced. However, it's important to remember that connection to a district heating grid is not always possible. If all prerequisites are met, the choice is often limited due to connection constraints. This also applies to the choice of provider. This is because operation of the grids and the heat generation plants is in the hands of a single company. There is no competition. Accordingly, there is little leeway in terms of running costs. These can vary greatly depending on the price calculation performed by the providers.