ACER is preparing an open-source model to assess electricity flexibility needs across Europe, as a 3 MW demand-response activation in Romania shows how consumers can provide balancing services. The European Union Agency for the Cooperation of Energy Regulators announced on October 21 that it would release a preliminary version of EU-Flex. The model is intended to measure where power systems need additional flexibility, how much they need and where existing resources fall short.
A consultation on EU-Flex will run from November 5 to December 17, 2026, before ACER’s first EU-wide flexibility-needs assessment, planned for July 2027. European regulators are preparing a framework for measuring power-system flexibility requirements that could support commercial markets for industrial consumers, aggregators and distributed energy operators. In those markets, participants could earn revenue by changing when or how they use electricity.
The immediate change is methodological, not commercial: EU-Flex will not establish a trading platform, authorise investments or guarantee payments to flexibility providers. Its value for Southeast European markets could lie in making flexibility a measurable service that can be contracted and potentially financed, rather than treating it solely as an operational requirement.
Consumers as flexibility providers
Electricity markets have traditionally valued industrial consumers for the power they buy and the predictability of their demand. A different source of value is emerging when a consumer can alter consumption in response to a verified request. A factory able to cut demand for a predetermined period may be able to sell that reduction as a service.
Refrigeration facilities, heating systems, water pumping stations and EV charging operators may likewise be able to move some activities to different times without materially disrupting their primary business. Such facilities would remain electricity customers while also becoming potential suppliers of flexibility. Reduced demand is not generation, but it can sometimes give the system a balancing response equivalent to increasing production.
Whether participation is commercially worthwhile depends on payments exceeding the costs of operational disruption, additional equipment, administration and contractual liabilities. Aggregators can combine the flexibility of many consumers into portfolios large enough to meet minimum participation thresholds and provide a more dependable service than individual small sites. Their business model requires digital controls, metering, consumption baselines, dispatch instructions and settlement arrangements.
Romania activates demand-side reserve
Romania has moved from regulatory provision to an operational example. On September 1, 2026, transmission system operator (TSO) Transelectrica activated a balancing reserve group made up entirely of controllable electricity demand. Organised by Romanian aggregator Flexumers, the portfolio delivered a 3 MW demand reduction during a 30-minute activation in the manually activated frequency restoration reserve market.
The reserve came from consumers lowering their electricity use, rather than from a power plant or an electricity-storage installation. Romanian rules set a 1 MW minimum participation threshold for relevant balancing services, enabling smaller consumers to take part collectively through an aggregator. The activation showed that a group of consumption points could meet technical qualification requirements and follow a system-dispatch instruction.
Romania’s regulator, ANRE, separately approved a consumption-flexibility mechanism in August. It allows eligible consumers, suppliers and aggregators to offer voluntary demand reductions. Transelectrica assesses the flexibility needed, participants submit price and quantity offers, and performance is checked against established consumption baselines using measured data.
Together, the mechanism and the activation show how demand-side resources can take a more active role in system operation. They do not establish the eventual size, annual turnover or sustainable profitability of the market. Those outcomes depend on how often resources are activated, the volumes procured, competing resources and remuneration rules.
Common method for assessing needs
EU-Flex follows ACER’s approval in July 2025 of a methodology for national electricity flexibility-needs assessments. Under the EU electricity-market framework, Member States were required to complete national assessments by July 2026. They are expected to set indicative objectives for non-fossil flexibility by January 2027.
The methodology distinguishes flexibility needed across an entire power system from flexibility required to manage network constraints. That distinction matters in Southeast Europe because national systems do not have identical technical or commercial requirements. One country may need resources to handle rapid changes in national demand, while a distribution area may need local demand reductions to prevent infrastructure overloads.
Different needs call for different services, procurement methods and contracts. A national flexibility shortfall does not, by itself, establish demand for a particular privately developed asset. Investors must determine whether the relevant system operator can buy the service, whether a provider can qualify and what revenue is reasonable to expect. An open EU-Flex methodology could let investors and regulators test the assumptions behind those assessments more transparently.
Regional markets develop at different speeds
Romania now has an operating example of aggregated industrial demand providing balancing services. Croatia introduced an upgraded balancing platform in September 2026, changing how reserve capacity and balancing energy are offered and creating conditions for more flexible participation. In Bulgaria, limited demand-response participation and low smart-meter penetration remain barriers.
The European Commission’s 2026 country assessment identified Bulgaria’s underdeveloped demand response as an obstacle to more flexible electricity-market operation. Serbia, meanwhile, has included aggregation and independent aggregators in its energy legislation, with provisions allowing eligible customers to contract with independent aggregators. Its regulator also consulted on procedures for switching suppliers and aggregators in August 2026.
For industrial consumers in Serbia, controllable production schedules, auxiliary processes and other flexible loads could eventually become revenue-generating services. Legislation alone does not make a market operational: participation also requires technical qualification, data exchange, settlement rules and enforceable commercial arrangements. Montenegro and other Western Balkan markets could examine similar structures as their electricity-market rules and digital infrastructure develop.
Aggregation changes the financing model
Aggregation presents investors and lenders with a proposition different from conventional electricity generation. An aggregator may own little physical energy infrastructure, investing instead in software, automation equipment, metering integration, customer acquisition and operating systems. Revenue may come from reserve availability, actual dispatch, customer services or contracts under other authorised flexibility mechanisms.
Such a business more closely resembles a technology-enabled energy-services company than a conventional power-plant operator, but it still presents underwriting challenges. Portfolio revenue depends on retaining customers, delivering verified responses, maintaining regulatory access and the continuation of market procurement. Profitability also requires clearly defined settlement among the aggregator, participating consumers, electricity suppliers and balance-responsible parties.
If a factory cannot reduce demand during a contracted activation, the aggregator may incur penalties or replacement costs. Revenue forecasts therefore need to reflect the reliability of industrial processes, not just their theoretical flexibility. A diversified portfolio can reduce exposure to individual customers, but cannot remove risks that affect several customers at once.
Measurement underpins market participation
Reliable evidence of delivered flexibility is essential to turning a demand reduction into a recognised market service. Metering, secure communications, operational records and independently reviewable consumption baselines determine whether the reduction can be verified. Smart meters and industrial energy-management systems may consequently gain a direct revenue function beyond billing and efficiency monitoring.
The November consultation will allow regulators, system operators and market participants to examine how EU-wide flexibility needs are modelled. Investment implications will depend on the later translation of assessed needs into procurement mechanisms, eligibility rules and revenues. In Southeast Europe, Romania’s activation provides an immediate operational example, while ACER’s model provides a longer-term regulatory framework for making industrial and distributed flexibility a reliable service; doing so before traditional electricity companies establish the emerging customer relationships is part of the commercial opportunity.
