The Brussels Air, Climate and Energy Code (CoBrACE) provides the overarching framework for climate action in the Brussels-Capital Region. Regarding water bodies, the Plan Communal Eau (Water Management Plan) addresses all water-related issues, including rivers, ponds, groundwater, drinking water supply, and flood management. The Ordinance on the Organisation of Thermal Energy Networks and Measuring Thermal Energy Consumption establishes the legal framework for the organisation of thermal energy networks (i.e. heating and cooling networks) and the measurement of thermal energy consumption, thereby providing the general framework within which AQE-based heating and cooling networks can operate; it does not, however, contain AQE-specific provisions. In addition, Brussels Environment supports the development of AQE through initiatives linked to the Port of Brussels and operates the continuous FlowBru hydrological monitoring network and publishes FlowBru and BruWater datasets containing flow rate and temperature data for regional water bodies. These datasets are essential for preliminary AQE studies and are used to support environmental permitting procedures.

Brussels Environment also launched comprehensive decarbonisation studies in 2025, which concluded that all renewable heat sources, including AQE, will be needed to achieve regional climate objectives. The studies identified district heating networks as competitive and climate-efficient solutions and highlighted key barriers to further deployment, including high costs, skills shortages, technical and regulatory challenges, and the absence of a clear long-term vision which are key elements in shaping related policies. One outcome of this work is the development of a regional heat zoning map, expected to be published in 2026.

Despite these generally supportive policy developments, important regulatory gaps remain. Current AQE-related provisions primarily focus on heating applications, while the CoBrACE framework for cooling remains insufficiently developed, despite the growing need for sustainable cooling solutions. Furthermore, legislation regarding discharges and extractions from surface water for thermal use and its interpretation is not specified in detail. Although recent COBRACE amendments have strengthened support for the renewable energy transition and the regional government continues to pursue decarbonisation objectives, a lack of political momentum, regulatory clarity, and long-term strategic vision continues to limit AQE development.

Brussels provides several funding and financing instruments that can support sustainable energy investments and individual projects. Examples include finance&invest.brussels​ and the ECORENO and ENERGY&RENO loan schemes. However, these instruments are general financing mechanisms and are not specifically targeted at AQE.

The current low price of gas makes alternative technologies, such as AQE, less financially attractive, leading to an unfavourable price ratio for heat pump technologies. Additionally, the significant upfront costs of AQE infrastructure and district heating systems pose a financial barrier. No investment subsidy scheme specifically targeting AQE or heat network infrastructure is available at the level of the Brussels-Capital Region; only general premiums and co-financing are available.

In practice, the permitting process takes up to one and a half years (observedproject experience; statutory decision periods are shorter), but the exact dates are usually unclear, and it is possible that the process will be extended. Costs can amount to several thousand euros and are generally unclear. The large number of different permits and unknown requirements lead to increased complexity, and the interdependencies between the different authorities pose a risk of delay. Individual heating choices that do not align with AQE can hinder the development of district heating networks, as can the lack of clarity surrounding AQE regulations. The environmental administration has so far only developed a limited framework for AQE.

In Brussels, engaged stakeholders are the authorities responsible for water management. Furthermore, Innoviris.Brussels provides subsidies for the implementation of new heat network technologies, and Ecobuild.Brussels is a network of sustainable and circular construction and renovation actors.

The local policy is a barrier to AQE development as it lags behind advancements in AQE regulation. Additionally, public perception remains low, and the potential of AQE is generally unknown and underestimated. Furthermore, many consultancy firms are questioning its financial and technical feasibility due to a lack of practical examples and knowledge. Bruxelles Environnement and the Homegrade platform provide some AQE awareness, but providing more practical applications and information could raise awareness and reduce the risk of public resistance.

In general, there is considerable potential to accelerate AQE deployment in Brussels through clearer regulations on AQE, district heating networks, and permitted infrastructure. A more favourable legal framework for urban planning, environmental permitting, and the installation and operation of heating networks would further support project development. The recent comprehensive heating and cooling assessment conducted in accordance with Article 25 of Directive 2023/1791, together with the decarbonisation study by Bruxelles Environnement, identified AQE as an economically attractive renewable heat source for district heating. The results of these assessments are expected to play an important role in shaping future policies, regulations, and strategic planning documents.

The BCR is targeting climate neutrality by 2050, with district heating recognised as a key component of the transition and AQE identified as a priority renewable heat source. Continued growth of AQE projects is expected along the Brussels Canal and the Zenne. In addition, the phase-out of fossil-fuel heating is progressing. From 2025, new residential buildings can no longer be equipped with gas or oil boilers, and the installation of oil boilers is generally prohibited.

Nevertheless, significant barriers remain. Financial support needs to be expanded and capture fees should be reduced. The price gap between gas and electricity continues to weaken the business case for heat pump-based technologies, making targeted subsidies particularly important. Regulatory uncertainty, fragmented policies, and limited political support also continue to slow development. Furthermore, individual project assessments remain time-consuming; therefore, the development of standardised tools and procedures could simplify applications and help unlock AQE potential. Authorities working on AQE-related policies and integrating them into heat zoning plans will contribute to environmental goals such as the National Energy and Climate Plan (NEKP), which outlines the policy framework for Belgium's contribution to European energy and climate goals.

Structural constraints must also be considered. Brussels is geographically small and has only a limited number of suitable water bodies, mainly the Brussels Canal and the Zenne. In addition, limited awareness of AQE and of the technology itself remain significant challenges. More example projects, improved knowledge sharing, and broader public engagement would further strengthen acceptance and highlight the environmental benefits of AQE, while supporting a transition towards more collective and sustainable heating solutions.

Flanders has a climate action plan, the Vlaams Energie en Klimaatplan, that aims to mitigate the effects of climate change and accelerate the transition to a low-carbon economy. The Kaderrichtlijn water (water code) provides an overarching legal framework for all water management rules and principles, while the River Basin Management Plans are specific to river basins. The latter's objective is to maintain and improve the quality of surface water and groundwater, prevent flooding and drought, and encourage the sustainable use of water.

Furthermore, Flanders is working on a spatial structure plan for AQE for which the province of East Flanders has served as a pilot region (ruimtelijk beleidsplan). Additionally, local energy and clima​te plans support municipalities and cities in addressing the challenges of climate change at a local level. However, legislation and its interpretation in Flanders relating to the discharge and extraction of surface water for thermal use are not always clear or straightforward. Legislation relevant to AQE was created for use in other sectors, resulting in a framework that is less applicable to AQE. However, the regulatory framework is currently under development.

Spatial and energy policies in Flanders are incoherent with regard to AQE, and testing is absent from the existing energy policy. However, a study examining the potential of AQE and the link between energy and spatial integration is currently being conducted. This will include an analysis of the most suitable locations for AQE, taking into account spatial features such as critical natural zones, types of energy consumers, and areas of high population density.

In Flanders, only general funds and programme support for green innovations are available. The Flemish government provides subsidies for heat pumps in renovations and offers investment support through its "Call for Green Heat" programme for those investing in new green heat, residual heat or energy-efficient district heating projects. Additionally, private companies receive support from the GREEN investeringssteun (Green Investment Fund).

Despite this investment support, the price ratio between natural gas and electricity is high (gas is four times cheaper than electricity per unit), which makes AQE less attractive. However, from 2028 onwards, a planned Flemish energy tax shift will gradually transfer costs from electricity to fossil fuels used for heating, aiming to make electrified heating solutions more financially attractive.

The investment cost of infrastructure and AQE heat networks is high, and there is no financing available for the study costs of AQE developments. Moreover, subsidies for heat networks are limited. Additional investments are required to make a building heat pump-ready, and levies and taxes apply. Finally, the capture fee payable to De Vlaamse Waterweg (Flemish Waterways) makes AQE less financially attractive when extracting water from navigable waterways.

The permitting process takes about half a year, but an extension due to revaluation is possible. Costs can range from a few hundred to a few thousand euros, depending on the size of the project. However, AQE faces a challenge due to inconsistencies and a lack of homogeneity between different watercourse managers. In terms of procedural clarity, the CIW (a Flemish waterway organisation that also works on AQE) operates entirely informally within the current framework. The CIW aims to clarify and improve the practical applicability of the AQE policy. Therefore, the current framework is being updated and will be linked to an AQE potential map, expected by the end of 2026, as well as a local assessment tool for permitting at the Flemish level, expected in 2027. The potential map will help identify areas with AQE potential, while the assessment tool will allow individual projects to check whether they are in line with the blueprint regulatory framework.

Challenges include the distribution of heat from water, uncertainty in urban planning about underground constructions, and the availability of water and potential. There is an information gap, and the potential of AQE is either unknown or underestimated. In the future, issues related to the distribution of heat in public water bodies may arise; at present, the spatial planning study seeks to avoid a 'first come, first served' approach. So far, Flanders has adopted a very individual approach to heating, whereas AQE is more suitable for collective heating.

Cities, municipalities and provinces in Flanders are considering using AQE as a source of clean heat for their heritage sites and territories. Energy brokers (energiemakelaars) and energy cooperatives are communities that share experience and knowledge, and that work together. Additionally, the CIW, organised by the Flemish Waterways, is a specific structure that organisations such as the Environmental Agency and the provinces are part of. However, local AQE policies are lagging behind and failing to keep pace with advancements in the field. Additionally, public perceptionremains low, with the potential of AQE being generally unknown and underestimated. Furthermore, many consultancy firms are questioning their financial and technical feasibility due to a lack of practical examples and knowledge. Providing more practical applications and information could raise awareness and reduce the risk of public resistance.

A study is being conducted to map the potential for AQE across the Flemish region. Governmental authorities, such as De Vlaamse Waterweg and the Vlaamse Milieumaatschappij (Flemish Environmental Agency), are also developing policies related to AQE. Furthermore, AQE has been incorporated into heat zoning plans, with the prospect of it becoming a reliable and accepted technique.

In general, there is high potential for improvement if the regulations regarding AQE, district heating networks, and types of permitted infrastructure are clarified, and if a favourable legal framework concerning urban planning and environmental regulations for the installation and operation of heating networks, including AQE, is established. Financial support must be increased and capture fees reduced. Investment in AQE needs to increase, but the price difference between gas and electricity creates a financial obstacle, threatening heat-pump-based technologies. Subsidies would encourage AQE uptake. Furthermore, a lack of political support and incomplete policies hinder the development of AQE. Single case treatment is time-consuming; therefore, a permit assessment framework tool to streamline and clarify application procedures will help realise AQE's potential. Authorities working on AQE-related policies and integrating them into heat zoning plans will contribute to environmental goals such as those outlined in the National Energy and Climate Plan (NEKP), Belgium's framework for achieving European energy and climate goals.

However, lack of awareness, distribution issues, and regulatory uncertainty pose a structural threat to AQE deployment. Therefore, full AQE integration is essential. In general, heating needs to become a more collective effort, rather than being based on individual heating choices. More AQE examples and knowledge would benefit public acceptance and increase awareness of the environmental benefits.

The Covenant of Mayors in Wallonia is part of a broader European initiative, whereby local authorities pledge to reduce CO₂ emissions and address climate change mitigation in accordance with the Walloon Air, Climate and Energy Plan (PACE). The Walloon Environmental Code of 27 May 2004 establishes the framework for Walloon environmental legislation on topics such as water, waste, and environmental permits. Within this framework, the Code de l'Eau (Water Code) regulates water use and management and includes provisions relevant to the use of water bodies for thermal energy extraction. Recent amendments introduced a specific procedure for domain authorisations on watercourses and a new category for surface water abstractions relevant to AQE projects. The Code also recognises the public interest of renewable energy projects and allows certain modifications of water body status where justified.

The Walloon Decree of 15 October 2020 on the Organisation of the Thermal Energy Market and Thermal Energy Networks establishes the legal framework for the thermal energy market and district heating, defining the roles of operators, suppliers, and users, while requiring local authorities to assess opportunities for thermal networks. In addition, the Walloon Decree of 29 April 2024 on Accelerating the Deployment of Renewable Energies introduced renewable energy acceleration zones, simplified environmental assessment procedures, exempted non-geothermal heat pumps below 50 MW from EIA requirements, and recognised renewable energy projects, including AQE, as being of overriding public interest. The General Regulation on Classified Installations of Wallonia includes provisions for classifying and granting permits for installations that may have an environmental impact, including those related to AQE. Furthermore, a significant step forward was taken with the Wallonia Heat Strategy 2024, which includes a dedicated annex on AQE and provides the first regional assessment and mapping of AQE potential.

Nevertheless, important regulatory gaps remain. The Walloon regulatory framework may not always keep pace with technological advancements in AQE, leading to situations where innovative AQE technologies face outdated or opposing regulations between water code and the maximisation of renewable energy hinder deployment. Further challenges include uncertainty regarding domain concession fees on navigable waterways, the continued use of gas in new residential developments, and a lack of coherence in terms of spatial and energy policy. As a result, AQE implementation remains constrained by regulatory uncertainty, insufficient standardisation, and limited planning integration.

Wallonia organises specific calls for green projects. For instance, there is currently an open call for projects that support the development or expansion of thermal energy networks. The region promotes sustainable energy solutions by financing projects that optimise energy distribution and reduce CO₂ emissions. Furthermore, financial support is available for energy efficiency and renewable energy projects.

A barrier to AQE development is the price ratio between natural gas and electricity (gas is priced at four times the rate of electricity). The costs of AQE infrastructure and heat networks are high, and no financing is available to cover the costs of developing AQE. Furthermore, subsidies for heat networks are limited. Additional levies and taxes pose a further barrier to AQE. A capture fee reduces the financial incentive for extracting water from navigable waterways. Ultimately, no specific AQE subsidy scheme exists.

Obtaining permission in Wallonia takes about half a year, but an extension by revaluation is possible. Permission costs can amount to a few thousand euros, with additional unknown costs. The number of authorities involved, as well as the interdependencies and inconsistencies between them, increases the complexity of the process and the risk of delays. The Walloon Decree of 11 March 1999 on the Environment Permit introduced the concept of coordinated permitting and environmental monitoring, and AQE projects based on heat pump technologies may benefit from simplified procedures.

There are specific regional regulations and limits on the discharge of non-domestic wastewater, including cooling water. In addition, the introduction of rubric 41.00.05 through the AGW of 23 May 2024 provides a first classification basis for surface water intakes, but sector-specific AQE guidance (comparable to the CIW Blueprint in Flanders) remains absent. As a result, a lack of information and standardised assessment methods can lead to AQE potential being overlooked or underestimated. For the allocation of thermal resources in public water bodies, a “first come, first served” approach is currently applied. So far, Wallonia remains characterised by a predominantly individual heating market, whereas AQE is generally better suited to collective heating systems.

Several authorities provide support and guidance on sustainable energy, including AQE and water management. These authorities include the Walloon Association for Sustainable Energy, the AWAC (Walloon Agency for Air and Climate), the Walloon Energy and Sustainable Building Department and the SPW (Wallonia Public Service).

Barriers to AQE development include local policies that lag behind in terms of AQE regulation, failing to keep pace with advancements in the field. Although local authorities are required to conduct opportunity studies under the thermal energy networks decree, awareness of AQE among both decision-makers and the public remains limited, and its potential is often underestimated. Furthermore, many consultancy firms are questioning its financial and technical feasibility due to a lack of practical examples and knowledge. The absence of dedicated Walloon communication and awareness campaigns further contributes to low visibility and acceptance. Expanding the number of demonstration projects and improving knowledge dissemination could help raise awareness, increase confidence in the technology, and reduce the risk of public resistance.

In general, there is high potential for improvement if the regulations regarding AQE, district network heating, and types of permitted infrastructure are clarified, and if a favourable legal framework concerning urban planning and environmental regulations for the installation and operation of heating networks, including AQE, is established. Additionally, financial support must be increased and capture fees decreased. Investment in AQE needs to increase, but the price difference between gas and electricity creates a financial obstacle, threatening heat-pump-based technologies. Subsidies would encourage the uptake of AQE. Furthermore, a lack of political support and incomplete policies hinder the development of AQE. Single case treatment is time-consuming; therefore, developing a tool to streamline and clarify application procedures would help realise AQE potential. Authorities working on AQE-related policies and integrating them into heat zoning plans will contribute to environmental goals such as the National Energy and Climate Plan (NEKP), which outlines the policy framework for Belgium's contribution to European energy and climate goals. In this context, the designation of renewable energy acceleration zones from 2026 onwards represents an important opportunity to facilitate the deployment of AQE systems and strengthen their role within the future heating mix.

However, ignorance of the technology itself, distribution issues, and regulatory uncertainty pose a structural threat to AQE deployment. Therefore, full AQE integration is essential. In general, heating needs to become a more collective effort, rather than being based on individual heating choices. More AQE examples and knowledge would benefit public acceptance and increase awareness of the environmental benefits.

In France, heat planning is largely voluntary, although some elements are integrated into mandatory local energy and climate action plans of intercommunalities (gatherings of municipalities). Since the adoption of the Energy Transition for Green Growth Act in 2015, intercommunalities with more than 20,000 inhabitants have been required to develop Sustainable Energy and Climate Action Plans (SECAPs) that include measures for the decarbonisation of heating and cooling. In addition, the Plan Climat-Air-Énergie Territorial (PCAET) provides a six-year plan for local climate mitigation and adaptation actions.

Regarding AQE, the Guide PAC eau de mer (seawater heat pump guide) written by ADEME (national agency for ecological transition) outlines the key elements for the development and operation of a seawater heat pump project. ADEME (agency for ecological transition) also provides national funding for AQE projects based on specific eligibility and funding conditions and participates in project steering committees, where it supports knowledge exchange and project evaluation.

Nevertheless, several regulatory inconsistencies remain. One key contradiction is the 5°C temperature delta for water discharge, despite the possible alteration to 20°C for industrial purposes. In addition, many riverside areas are covered by flood risk prevention plans (PPRL), which can prohibit the construction of energy production facilities intended to supply customers outside the designated flood area. However, the EnR'Choix matrix, introduced in 2025, supports decision-making by comparing renewable energy technologies (including biomass, geothermal energy, solar thermal energy, and AQE) based on resource availability, technical feasibility, economic performance, environmental impacts, and governance considerations for a specific site, building, or territory.

The inconsistencies highlight significant gaps in the French regulations, particularly regarding water abstraction and discharge, environmental assessment procedures, multi-energy systems, and viable business models. Ongoing debates concerning water body protection may further affect AQE development. At the same time, recent political developments have negatively impacted the budgets allocated to developing renewable energies. In addition, limited awareness of AQE among policymakers and decision-makers continues to hinder the adoption of this relatively new technology.

The Fonds Chaleur (heat fund) provides grants covering up to 65% of investment and 70% of study costs for renewable heat projects, including geothermal energy, biomass, solar thermal energy and district heating networks. Eligibility is limited to public authorities and private entities with a SIRET registration number. Project owners may apply directly to ADEME or through their local representative, the Territorial Renewable Heat Contract Coordinator (CCRt).

Additionally, there are several citizen-led funding networks (Lumo Investments, Energie Partagée and Taranis) that support public participation in renewable energy projects through both financial investment and involvement in decision-making processes, thereby promoting a more inclusive and sustainable energy transition. These initiatives remain minor, with high borrowing rates thereby restricting access to loans for citizen-led groups.

Nevertheless, financial barriers remain. There is currently no dedicated funding system targeting AQE, as it is mainly designed for geothermal energy systems.

As a result, available funding is fragmented across different permitting frameworks. In addition, the perceived investment risk of AQE technologies is often overestimated, restricting project development largely to major companies with substantial financial resources, such as IDEX, Dalkia, Engie. Furthermore, current electricity prices (based on nuclear energy) and relatively low gas prices continue to reduce the economic competitiveness of renewable heat solutions, leading to huge investments costs for alternative energy sources on DHC and individual systems.

The permitting process for AQE projects in France can take up to two years, with variable processing times depending on the type of authorization; except for archaeological diagnosis whose duration cannot be reliably assessed. The cost of an operating licence ranges from 20,000 to 30,000 euros, while a declaration file costs 15,000 euros. The lack of transparency regarding administrative requirements makes overall project costs difficult to estimate. Moreover, the large number of permits involved, and their interdependencies create significant procedural complexity, leading to extended validation periods and increased project risks.

Although the regulatory framework is broadly aligned with renewable energy development, it is not yet fully adapted to AQE. In practice, thermal design offices tend to focus on geothermal heat solutions, while many technical experts have limited awareness or experience with AQE technologies.

Public authorities such as ADEME, regions, DDT (Direction départementale des territoires), DREAL and cities play a central role in supporting the transition towards sustainable energy systems. Community-led approaches, including AQE projects, have significant potential to accelerate this transition. However, their success depends strongly on social acceptance, making misinformation a substantial risk. Misconceptions about the visual and environmental impact of AQE installations – such as concerns over apparent pipelines on beaches or harbours – have led to public opposition. Raising public awareness and providing reliable information are therefore essential for AQE project development and acceptance.

In the short term, several AQE projects are planned at the local scale. These projects can serve as valuable demonstration cases, paving the way for replication and upscaling. Larger projects are also beginning to emerge, but additional reference projects are still needed to support the evolution of the regulatory framework. Continued research and monitoring of AQE systems at all scales would help provide the evidence needed for environmental authorities and permitting bodies to assess projects more effectively and, where appropriate, adapt existing criteria and requirements.

At present, air heat pumps dominate the individual heating market. By contrast, AQE remains relatively unknown and should increasingly be considered for larger-scale applications, particularly in DHC networks. Although new DHC networks are being developed, especially in southern France, many of these projects place a stronger emphasis on cooling than on heating.

In the long term, structural reforms will be essential if AQE is to play a significant role in the renewable energy transition. The explicit integration of AQE into policy frameworks and support structures would facilitate project implementation. Clearer environmental guidelines and technical standards (e.g., delta T) could streamline environmental impact assessments and improve infrastructure potential. Nevertheless, environmental barriers related to protected areas and biodiversity protection are likely to remain in the future.

In addition, ADEME could consider easing the eligibility criteria for AQE-related grants, which are currently difficult to meet for projects based entirely on heat pump technology. The absence of AQE-specific support mechanisms continues to limit investment and favours a small number of well-resourced actors. Another structural challenge is the limited capacity and awareness of thermal design offices to integrate AQE solutions. However, the national environmental agency has created a matrix to help prioritize renewable energy, including AQE.

Public perception and misinformation also remain a critical factor. Misconceptions about the environmental impacts of AQE can hinder project acceptance and delay implementation. NGOs could therefore play an important role in raising awareness, disseminating reliable information, and encouraging community participation in AQE initiatives. Ultimately, wider deployment of AQE could contribute directly to the objectives of ADEME and DREAL by strengthening climate resilience and supporting the transition to a sustainable, low-carbon energy system.

Germany has adopted a climate protection law (Klimaschutzgesetz), legally committing the country to achieving greenhouse gas neutrality by 2045 through a comprehensive climate strategy. To support this, the Wärmeplanungsgesetz (Heat Planning Act) requires all municipalities to develop comprehensive municipal heat plans (Kommunale Wärmeplanung) by 2026 and 2028, respectively. These plans must include an assessment of existing heat supply structures and the potential for renewable energy sources, including AQE. Furthermore, the law sets national targets for grid-based heat from renewable sources or unavoidable waste heat. Additionally, the Kommunalrichtlinie (a municipal guideline) supports municipalities in reducing their emissions sustainably by providing funding for feasibility studies, consultancy services, municipal networks and energy-saving models. The Gebäudeenergiegesetz (Building Energy Act) actively promotes renewable energy sources, encouraging communities to adopt renewable energy technologies. The amendment of the Water Resources Management Act (Wasserhaushaltsgesetz, WHG) in 2025 explicitly addresses the thermal use of surface water and defines permission rules and processing times for applications. Different maximum processing periods apply depending on whether the temperature reduction of the discharged water is below or above 1K.

However, AQE remains insufficiently defined in existing regulations. There are still no established standards for determining either the share of a water body’s thermal capacity that may be utilised or the minimum distance required between consecutive AQE systems along flowing waters. Additional barriers arise from slow policy standardisation and limited political communication. Due to low public visibility and perceived environmental risks, which are often exaggerated in the absence of reliable data, policymakers tend to underestimate AQE’s potential. At the same time, the current federal government is discussing a relaxation of the planned phase-out of fossil fuels in residential heating, reflecting generally lower ambition regarding Germany’s climate targets. These developments influence the availability and communication of information related to AQE. The political agenda development influences potential information and communication.

The state development bank offers grants and loans for renewable energy and heating systems, but there is no specific funding available for AQE. Although a national grant for efficient heating networks exists and various regional funding schemes are available, access often depends on project-specific evaluations and the decisions of local authorities. Furthermore, the high initial costs of implementation and infrastructure continue to present a significant financial obstacle to the deployment of AQE.

Efforts to harmonise permitting procedures were strengthened through the 2025 amendment of the Water Resources Management Act (WHG), which introduced legally defined processing periods. Authorities must decide on permit applications for heat pumps with a capacity of up to 100 kW that use surface water for thermal purposes and cause a maximum temperature reduction of 1 K within three months. For larger AQE projects, the permitting process must generally be completed within one year, with a possible extension of up to six months in specific cases. In addition, authorities are required to provide procedural guidance for the permitting process.

Despite these improvements, permitting fees remain unclear, and the process is further complicated by uncertainties regarding the responsibilities of the relevant administrative bodies. Standardised procedures are still lacking, as the interpretation and application of regulations vary between local authorities. The law defines a temperature threshold that determines the applicable processing period but does not establish the process itself. Instead, potential impacts on the overall temperature of the water body are assessed as part of the EIA. Although the maximum processing period for a valid application is 18 months, slow procedural adaptation continues to hinder AQE project development. Authorities often lack a consistent framework for decision-making, and permitting practices are not standardised across regions. As a result, applications are more likely to face delays or rejection when regulatory requirements are unclear, extensive, or complex.

An increasing number of research institutions are engaged in AQE projects, including the Technical University of Darmstadt and the Fraunhofer Institute. At the regional level, stakeholders are represented by actors such as energy agencies (Landesenergieagenturen). Although public scepticism remains due to a lack of information, it is reduced through education and demonstration, leading to gradually increasing acceptance. For instance, the Kompetenzzentrum Kommunale Wärmewende (KWW) promotes communication and engages with communities to facilitate the heat transition.

The 2025 amendment of the WHG has partly mitigated a major barrier to AQE by introducing binding timeframes for permit decisions. However, AQE continues to face structural challenges, including unclear administrative responsibilities, fragmented standards, and the absence of nationwide guidelines. Standardised regulations and governance structures could significantly improve deployment and support Germany’s goal of climate neutrality by 2045. In particular, reducing barriers to the construction of new infrastructure and increasing recognition of AQE within the renewable energy mix are essential.

The ongoing development of support structures and decreasing costs for AQE relative to fossil-based systems would further reduce financial barriers, making it a more attractive option. While gas prices are expected to increase in the long term due to rising network charges, declining gas consumption, and the introduction of ETS II carbon pricing, procurement costs on spot markets are projected to decrease.

Nevertheless, progress remains slow. Political priorities strongly influence public communication, often amplifying perceived risks due to a lack of information, which threatens the development of AQE. Increased public education and the availability of information, as well as stronger political will, are crucial to overcome scepticism and prejudices towards environmental impact, and to advance AQE deployment. Recent political debates on weakening or reversing measures aimed at phasing out fossil fuels in domestic heating (e.g. Building Energy Act), have raised concerns about the future implementation of green heating technologies. This creates uncertainty regarding the market demand for community-based and large-scale renewable heating solutions in the next years, including AQE.

Despite these challenges, research institutions, energy authorities, and renewable energy experts recognise the significant technical and environmental potential of AQE, especially given Germany’s abundant water resources. In addition, the municipal heat planning provides a framework for the evaluation of local conditions and requires municipalities to develop heat plans by 2026 for cities with over 100,000 inhabitants and by 2028 for smaller municipalities. These plans are technology-neutral and encourage diverse renewable solutions, including district heating, heat pumps and climate-neutral gases. The law also sets clear targets, namely that by 2030, half of all grid-based heating should be climate-neutral, with renewable or waste heat contributing at least 30% by 2030 and 80% by 2040. While this creates opportunities for AQE integration, the absence of AQE-specific regulations could result in a greater emphasis on more well-established technologies.

Ireland has implemented a Climate Action Plan which sets out the goal of providing 2.7 TWh of district heating per year by 2030, with AQE could being a key source of this. The government additionally aims to enable Ireland to transition to a low-carbon, climate-resilient and environmentally sustainable economy within EU and global frameworks. By 2030, it intends to meet the targets of up to 80% renewable electricity, a 30% reduction in CO₂ emissions and a 32.5% improvement in energy efficiency. While Ireland's policies and frameworks relate to renewable energy, heating and cooling, none of them mention AQE directly. This is expected to cause issues with the rollout of AQE. Furthermore, if policy and financial support for AQE development is too slow and there is a lack of focus on this area, regulations will remain a major barrier to its implementation.

The climate action fund is a general financial support in Ireland. The community climate action fund, launched in late 2024 and early 2025, currently represents one of the most promising funding opportunities for community-based AQE initiatives. In addition, several other grant schemes may be used to support AQE project development. However, there are no dedicated mechanisms to bridge project development costs, nor are there tax incentives.

At present, policy and funding efforts remain focused on individual projects and feasibility studies. As a result, investment readiness remains constrained by the lack of dedicated support structures and long-term funding pathways. Key financial barriers for AQE continue to be limited funding for research, project planning, and capital investment.

Information on permits, their requirements, validation criteria, costs or processing timesfor AQE remains limited. Permits related to water extraction and discharge for cooling have emerged as particularly relevant, and as projects and feasibility studies progress, these are becoming an important basis for permitting and planning permission. There is currently no specific permitting procedure for AQE in Ireland. Other structural barriers include a lack of information, resources, experts, services and developers.

Engaged stakeholders include the authorities responsible for water bodies and water-related management, as well as the local community, who may provide support for energy and sustainability. In addition, the SEAI (Sustainable Energy Authority) has developed a national group charged with the development of district heating in local areas to decarbonise heat.

Public awareness of AQE remains limited and continues to pose a barrier to wider deployment, as knowledge gaps lead to scepticism and resistance. However, understanding of AQE has improved through the work of the AquaCOM project. While public acceptance is gradually increasing, broader awareness and engagement remain important challenges.

The development of regulations, governance structures and policies for AQE could contribute significantly to the achievement of the country's climate protection targets by 2030. Targets relating to district heating already exist within the next 20 years (up to 2.5 TWh/year for residential buildings and up to 0.2 TWh/year for public and commercial buildings), as set out in the Climate Action Plan. Promoting the potential and technology of AQE and including it in policies as a source of district heating would benefit its future development, as well as encouraging a focus on small-scale, local district heating systems. AQE should be used as a heating and cooling source in district heating systems located adjacent to water sources. Case studies and proof of feasibility could encourage further AQE implementation.

However, the current lack of information, resources and experts, services and developers structurally threatens AQE development. AQE potential must also be increased by environmental regulatory policies. Improving financial support structures for AQE is essential, as current barriers include research funding, planning and feasibility funding, and capital investment. A political shift towards environmental targets would increase focus on AQE objectives, and greater awareness of the topic could be raised by providing more information.

The Project Ireland 2040, a national planning framework has been revised in 2025. The Project Ireland 2040 Delivery Board is a non-statutory board which provides strategic direction and leadership to the National Development Plan (NDP) and National Planning Framework (NPF) implementation process, including communication of Project Ireland 2040. There is high potential to reach the district heating targets with AQE, which would contribute to the climate action plan and a transition to a low-carbon, climate-resilient and environmentally sustainable economy.

In the Netherlands, the CO2 reduction goals, including achieving climate neutrality by 2050, are set out in the Klimaatakkoord (climate agreement), which encourages the transition to renewable energy. AQE specific policies currently exist only at a regional level. One example is the Frisian programme of Missy Wetterwaarmte, which is designed to stimulate the adoption of collective AQE systems, providing project development support and enhancing standardisation with the target of 20% of buildings heated collectively in Frysland by 2030. However, there are policy gaps: Low-temperature heat is not considered heat, meaning it has no tariff structure, which hinders the creation of a business case. Furthermore, the depreciation rates for collective systems are limited to 25 years, but a longer timeframe would be required.

AQE also faces political barriers due to limited experience within local governments, national political instability, and changed priorities. The District Heating Law continues to be under discussion and poses a barrier to AQE development. Additionally, the affordability of district heating poses a policy risk. Although gas prices are expected to rise and eventually will be phased out in the long term, it is presently used as a point of comparison with district heating network prices.

A variety of funds and subsidies are available to encourage sustainable development, renewable energy, heating solutions and CO₂ reduction. Some of these are specifically aimed at district heating solutions, such as WIS and Proeftuinen Aardgasvrije Wijken (natural gas-free neighbourhood testbeds). In addition, new financial mechanisms may support AQE deployment, such as the Nationaal Warmtefonds, which provides loans for investments in sustainable heating projects, and the Ontwikkelfonds Warmte, which funds R&D costs for heating projects, especially for cooperatives and communities. Furthermore, financial support is available for the implementation of individual and small heat networks with up to 250 connections.

Despite these funding opportunities, limited development and implementation capacity remains a significant barrier to AQE deployment. This challenge is compounded by the perceived financial risks associated with the development of district heating networks.

Most permits can be obtained within three to six months, except for those required for the heating company, such as the exploitation plan and tariff scheme. Permission costs vary depending on the size of the project and the different permits required and can differ in different areas due to the lack of standards. Authorities' and local governments limited knowledge and experience regarding AQE can be seen as a structural barrier. The requirement to measure water temperatures for a year before a permit can be obtained also hinders development.

Authorities responsible for water bodies, local initiatives, district heating companies, social housing, and energy and heating grid management companies are all active stakeholders. AQE promotion is interlinked with the heat transition on a regional level and local initiatives exist. For instance, the Province of Friesland develops heat grids and organises events through Wetterwaarmte and Friese Energietafel.

However, social acceptance of district heating remains a challenge. Public trust is often limited due to knowledge gaps, affordability concerns, leading to scepticism. Comfort and affordability are key factors influencing public perception, while a lack of experience and a clear long-term vision further slow adoption. Demonstration projects and successful practical examples could help increase confidence and accelerate deployment.

Furthermore, the Omgevingswet (Environment and Planning Act) requires stakeholder participation in projects involving environmental changes. While this supports public engagement, it can also make project development more time-consuming and complex.

District heating networks are expected to expand over the next 5–20 years, especially in Fryslân, where regional goals aim to connect 20% of buildings to collective systems, with significant emphasis on AQE systems. Growth in sustainable collective heating is expected to be driven by the planned introduction of the Collective Heat Act in 2026, the implementation of ETS II, and rising gas prices. AQE has potential to become one of several important heat sources within the Dutch energy transition, alongside industrial waste heat and geothermal energy. At the same time, growing demand for cooling and thermal energy storage creates additional opportunities for AQE. Future systems are expected to become more efficient through continued research and knowledge exchange with European partners, with hybrid heat networks increasingly combining AQE with other heat sources for thermal storage, regeneration, direct heating, and passive cooling. Growth is also expected in individual AQE systems and small-scale heat networks, when local conditions are suitable. To support this development, Fryslân aims to establish a subsidy scheme for individual and small-scale AQE projects.

Several barriers must still be reduced to enable wider deployment by knowledge sharing, clearer regulations, and the implementation of technical standards. The current unclear governance structure for AQE projects, as well as the lack of sufficient AQE specific structural support, poses a barrier to AQE development. In addition, environmental impact assessments (e.g. through filtration systems) need to be facilitated in order to establish standards. From an economic perspective, viable business models remain challenging, while competition with fossil-based heating continues to affect the attractiveness of AQE. Creating favourable economic conditions for sustainable and collective heating systems will therefore be essential. Transparency regarding pricing, governance, profits, planning, and expected levels of comfort, reliability, and cost will also be important for building public trust.

The planned District Heating Law (not yet accepted) could contribute to clearer regulation of tariff structures and governance of collective systems. Additionally, a nationwide stimulation programme for AQE systems, based on the existing regional approach, could support future growth. However, regulatory restrictions relating to dike bodies are unlikely to be relaxed and will probably remain a barrier. While large-scale AQE deployment could contribute significantly to achieving the Netherlands' climate goals, political priorities have recently shifted. The abandonment of the planned obligation for a sustainable solution in 2026 (warmtepomp verplichting) has reduced the sense of urgency among consumers. Combined with limited experience within local governments and recurring political instability at the national level, this creates additional uncertainty for the future development of AQE.