Manufacturers of heat pumps and other DERs (Distributed Energy Resources) are increasingly supporting and in some cases leading on trials to prove how assets can participate effectively in demand-side response activities, which is big news for the UK’s energy managers, says Peter Spurway, Head of Key Accounts & Strategic Partnerships at Viessmann Climate Solutions UK.
The electrification of heat is gathering pace across the UK, driven by decarbonisation targets, policy support and growing adoption of heat pump technology. Yet alongside the opportunities presented by this transition comes a significant challenge: how can the electricity grid cope with the additional demand created by millions of electrically powered heating systems?
For several years, demand-side response (DSR) has been touted as part of the answer. Instead of consuming electricity whenever heat is required, it uses smart heating systems to respond to signals from the grid, shifting loads away from peak periods to help balance supply and demand.
Until recently, however, much of the evidence supporting this approach came from modelling exercises and theoretical studies. Questions remained about whether residential heat pumps can reliably provide flexible grid balancing in the real world without compromising household comfort or system performance. These concerns have limited enthusiasm for DSR deployment.
Strong evidence
The recent completion of the three-year ViFlex project by Viessmann Climate Solutions in Germany now offers some compelling answers.
Working with German transmission system operators TenneT Germany and TransnetBW, Viessmann integrated more than 100 homes equipped with heat pumps directly into live network management systems. The aim was to explore whether live flexibility would impair household comfort levels.
Through fully automated controls, the heat pumps were able to respond dynamically to signals from the electricity network, relieving congestion and avoiding curtailment of surplus renewable energy. Over three consecutive winters, the programme delivered flawless grid reliability while maintaining desired service levels for residents throughout.
This represents the first solid, practical evidence that DSR can be delivered through decentralised heating systems without negatively affecting building users, and as such it’s of real relevance to energy managers in the UK.
Why flexibility matters
The challenge facing the country’s energy infrastructure is increasingly one of timing rather than overall generation capacity. As more renewable energy from e.g. wind and solar sources comes onto the network, supply becomes more variable. At the same time, electrification of transport, heating and industry is greatly increasing demand.
Managing these competing pressures requires greater flexibility across the entire energy system. Buildings effectively become thermal batteries, storing heat when electricity is plentiful and reducing consumption when the grid is under pressure.
For organisations with residential portfolios, public sector estates or commercial buildings, this creates opportunities that extend beyond carbon reduction. Flexibility services could potentially reduce exposure to peak electricity costs, improve resilience and create new revenue streams through participation in flexibility markets.
The technology behind ViFlex
A key element of the ViFlex project was interoperability. Historically, participation in flexibility schemes has generally required bespoke integration between individual building systems and energy management platforms. This complexity can limit scalability and increase costs.
ViFlex instead relied on standard application programming interfaces (APIs) that are already built natively into Viessmann products. These interfaces enable communication between the heat pumps and any other Viessmann or third-party technology such as aggregation platforms, battery storage, solar generators, or MHVR systems.
The API approach demonstrates how flexibility can potentially be embedded within heating systems from the outset, using technology that is readily available today. Numerous elements can be conveniently monitored and controlled via a single platform. This opens up the possibility to decarbonise buildings and equipment incrementally as budget and priorities dictate, with no limitations on which vendors’ products can be used.
For energy managers evaluating future heating investments, interoperability and digital connectivity are likely to become increasingly important considerations alongside traditional factors such as efficiency, reliability and capital cost.
Implications for the SSES
The timing of the ViFlex project is particularly relevant given the government’s Smart Secure Electricity System (SSES) initiative which will ensure distributed energy resources, including heat pumps, battery storage and EV chargers, play a growing role in load sharing and balancing the grid.
The SSES framework will govern how these smart domestic energy appliances are built and used, with requirements for intelligent capabilities, consumer-led flexibility (CLF) provisions, and a licensing regime for load controllers – the aggregators responsible for dispatching demand-side flexibility.
The ViFlex model, in which Viessmann acts as aggregator and controller, is precisely the type of architecture the SSES proposals are moving towards. For policymakers, network operators and technology providers, ViFlex offers a practical blueprint for how decentralised heating assets could contribute to future energy system resilience.
Lessons for energy managers
As electricity systems become increasingly dynamic, the ability to respond intelligently to network conditions will grow in importance. Flexibility is becoming a core capability rather than a niche innovation.
Connectivity is key to this. Buildings equipped with smart, interoperable systems will be far better positioned to participate in future flexibility markets than those relying on isolated technologies. Viessmann (part of Carrier) has an enormous installed asset base across Europe and can play a significant role for supporting tranmission networks and reducing green power curtailment – products such as the Vitotron electrode boiler, used predominantly for industrialised processes and heat networks, are available in sizes of up to 60mWth. Those solutions can unlock vast amounts of grid flexibility.
The ViFlex project itself highlights the importance of viewing heating systems as active energy assets rather than passive power consumers. Heat pumps are no longer simply a means of delivering warmth. Increasingly, they are becoming part of a wider energy ecosystem capable of supporting grid stability, reducing costs and contributing to net-zero objectives.
This article appeared in the July/August 2026 issue of Energy Manager magazine. Subscribe here.
