Frequently asked questions about municipal heat planning

The fundamental task is to develop a strategy for a long-term climate-neutral heat supply for the city of Aachen. The municipal heating plan shows the current status quo of the heat supply as well as various perspectives for a future heat supply, for example from renewable energy sources, waste heat or combined heat and power (CHP). The result of the heat planning is a non-binding recommendation on how the heat supply can be converted to be climate-neutral. The result of the heat planning is a non-binding recommendation.

The greenhouse gas balance of the city of Aachen from 2022 shows the heating sector as by far the largest source of greenhouse gas emissions with a share of 44 percent. Municipal heat planning can therefore make a significant contribution to reducing greenhouse gas emissions.

To date, the majority of heat supply in Aachen has been provided by fossil fuels. According to the final energy balance, less than 8 percent of the heating requirements of private households for 2022 were covered by renewable energies and over 80 percent by fossil fuels such as natural gas and heating oil. The heat planning shows how the heat supply can be converted to renewable energies and where energy efficiency measures should be implemented. It thus makes an important contribution to achieving the climate neutrality target by 2030.

The heat planning is drawn up for the entire urban area and comprises the main steps:

• Inventory analysis (current heat demand, greenhouse gas emissions, building stock, condition and existing networks)
• Potential analysis (possible energy savings and potential renewable heat sources)
• Target scenario (combination of existing and potential for a needs-based heat supply)
• Heat transition strategy and implementation strategy (recommended measures and corresponding implementation schedules)

The heat planning was carried out in close cooperation with the specialist departments and municipal utilities of the City of Aachen, STAWAG and Regionetz. Other local energy suppliers, housing cooperatives, companies, industrial enterprises, commercial facilities and institutions, as well as external experts, were involved in the process according to their needs or potential.

• Type and quantity of existing buildings
• Planned new buildings, neighborhoods and demolition
• Ownership structures of the buildings
• Current heat consumption, heat generator and energy source
• Usable heat sources
• Existing heating networks
• Current energy efficiency of buildings, refurbishment potential and refurbishment rates
• Topography (What is the terrain like?)

Essentially, heat is generated by combustion, by using renewable energies such as solar thermal energy or on an electrical basis such as heat pumps. The energy sources used for combustion include gas, oil, coal and wood. Solar thermal energy uses the energy of solar radiation. With heat pumps, heat from various sources is raised from a low temperature to a higher level by means of electricity and thus made usable for heating buildings. In addition to outside air, geothermal energy, waste water or thermal water can also be used as heat sources for a heat pump.

A special form of heat source is waste heat, where heat used for power generation or industry, for example, is reused and fed into a heating network.

Composting biomass produces heat, but this cannot be used to supply households on an industrial scale.

The most economically viable form of wind energy to date has been electricity generation.

Nuclear power is used to generate electricity and can also supply waste heat, but no longer plays a strategic role in Germany due to the decay radiation from the waste.

The Aachen-based KWP experts currently assume that there will be no conversion of the gas grid to a hydrogen grid. If at all, hydrogen will be supplied specifically to industry or power plants. Background: Hydrogen will remain a very scarce commodity worldwide for at least the next 20 years. Accordingly, hydrogen will only be used rarely, namely in areas where no or hardly any alternatives are possible, e.g. in industrial processes. Other alternatives for space heating, e.g. heat pumps or heating networks, are cheaper and also far more efficient. In addition, for technical reasons, hydrogen can only be added to the existing gas network in small quantities.

Central or pipeline-based heat supply takes place via a district heating network (via STAWAG) or so-called local heating networks. In the latter case, waste heat from conventional power plants, waste incineration, combined heat and power and combined heat and power plants (CHP), heat pumps, solar thermal energy or a mix of technologies are used as heat sources. Additional heat storage in grids ensures stability in the heat supply and can compensate for fluctuations in the availability of heat sources on a daily or seasonal basis.

Heat can either be generated decentrally, i.e. directly in or on the building, or centrally. In the case of centralized supply, the heat is transported to the buildings via a heating network, i.e. hot water pipes.

The municipal heating plan explains which type of climate-neutral heat supply is expandable and sustainable in which urban areas and districts. It analyzes the level of heat demand in the districts, the existing potential for heat sources (especially renewable ones) and the potential heat supply solutions for the future. Possible supply solutions include decentralized heat generation, e.g. with heat pumps, the use of local heat sources (local heating) or the strategic expansion of district heating. The heat planning therefore provides an initial guide for the selection of the future heat supply.
The recommendation of supply solutions for individual parts of the urban area has no legal consequences for the owners. Furthermore, there is no obligation to replace a functioning heating system.

Municipal heat planning provides initial information on the options that are available now and in the future. If you are looking for a decentralized solution for your building, altbau plus and the consumer advice center in Aachen offer good advice for building owners. If you would like to connect to a heating network, contact the operator of the heating network for more detailed information on connection options, deadlines and costs. Information and contacts for connecting to the district heating network in Aachen can be found on the STAWAG website.

According to the Building Energy Act (GEG), new heating systems (after transitional periods) must use 65% renewable energy. When connected to a district heating network, this requirement no longer has to be met by the building owner, but by the network operator. The district heating transfer station requires little space in the building/basement and no large heat storage tanks or storage areas for fuels such as wood pellets need to be provided. District heating also has the advantage that no local emissions are produced as the heat is generated centrally. This is a great advantage for air quality in cities. Please contact STAWAG directly with specific inquiries.

The legally prescribed municipal heating planning does not initially oblige connection to local or district heating networks. The decision to connect is therefore made by the building owner. Whether this will change, for example through bylaws for individual areas, will be determined by local political developments.

It should not and cannot. The task of municipal heat planning is to show where heat supply is possible in principle. No expansion guarantees or deadlines for connection to heating networks can be derived from heat planning. Only the heating network operators can provide binding information on this.

The "public" heating networks in Aachen belong to STAWAG. Connections to existing networks are already possible. STAWAG is generally responsible for deciding on the scope and timing of the further expansion of the heating networks. However, it has defined an ambitious district heating expansion area (FWA), which has been incorporated into the municipal heating planning and largely coincides with the potential area identified there. The FWA is to be fully developed with district heating by 2045 - as far as technically and economically possible. Information and contacts for connecting to the district heating network in Aachen can be found on the STAWAG website.

The requirements for heat generators are regulated in another federal law, the Building Energy Act (GEG). Since the GEG came into force on 01.01.2024, new heating systems must be able to be powered by at least 65% renewable energy. In existing areas, there is a transitional period that is linked to the legal obligation to draw up a municipal heating plan. In Aachen, this must be in place by 31.06.2026. But even in existing buildings, specifications must already be met today when installing a new heating system. Take advantage of the offer and get free advice from altbau plus or the consumer advice center in Aachen.

The energy balance of a residential building depends on the type of heat generation, electricity consumption and transmission heat loss: How much energy is lost through the outer shell?

If insulation measures are carried out, the energy balance improves. This means that the heating system requires a lower flow temperature. This also improves the energy balance.

Installing a regenerative heating system improves the environmental balance and the energy balance. Modern heating systems are more efficient than old appliances. If you have previously insulated your home, the new heating system can also be smaller.

You can reduce your electricity consumption by installing your own photovoltaic system and thus improve your energy balance.

Finally, the balance can be improved to a limited extent by changing behavior. However, reducing the target room temperature is only possible to a limited extent because comfort in uninsulated buildings suffers as a result. In a passive house, the room temperature can certainly be lowered, as the external walls do not get as cold due to the good insulation standard. Comfort does not suffer here.

This technology can also be used in existing buildings. This is one of the findings of a research project by the Fraunhofer Institute for Solar Energy Systems ISE. We recommend that you arrange an energy consultation if you have any questions about your individual building. Altbau plus will advise you individually on your property.

According to the Building Energy Act (GEG), the following options fulfill the 65 percent rule (Section 71 (3) GEG):

• Connection to a heating network
• Heat pump
• Direct electricity heating in particularly energy-efficient buildings (Section 71d (3) GEG)
• Use of solar thermal energy
• Gas heating, if it demonstrably uses at least 65 percent biomethane or biogenic liquid gas
• Biomass heating
• Hybrid heating (e.g. combination of solar thermal energy with gas boiler, Section 71h (3) GEG)

There is no general answer to this because it depends on the type of heating system, heat requirement, age and renovation status of the building. It is important to know that there are many funding offers that must be applied for before implementation begins. Altbau plus will advise you individually on your property.

This is difficult to predict. In the draft of the Building Energy Act, the Federal Ministry of Economics assumes that citizens across Germany will have to spend more than nine billion euros a year by 2028 to heat their homes in a more climate-friendly way. However, the ministry calculates that this would be offset by savings of around 11 billion euros, as oil and natural gas are likely to become more expensive in the coming years.

Central planning for the approximately 11,000 municipalities in Germany by the federal government is not expedient: Aachen knows better than Berlin what is good and right for Aachen.

On the other hand, a direct transfer of tasks from the federal government to the municipalities is not possible under constitutional law.

Aachen is tackling the future. Unfortunately, construction sites are inevitable. If you would like to find out more about current construction work and background information, you will find it here.