The ViFlex project, conducted in partnership with German transmission system operators TenneT Germany and TransnetBW, integrated more than 100 Viessmann heat pumps in private homes into live grid management operations over a period of nearly three years. The result is the first real-world, operationally validated demonstration that domestic heat pumps can contribute to demand-side flexibility – shifting electricity consumption in response to grid signals to relieve congestion and avoid curtailment of surplus renewable energy.

Heat pumps participating in the pilot were aggregated into virtual pools, organised by grid area, via the Viessmann Cloud. Load forecasts and available flexibility were submitted to the transmission system operators through the Equigy Crowd Balancing Platform – a European TSO initiative designed to harmonise the integration of small-scale, decentralised flexibility into system services markets. Activation signals from the TSOs were routed back through the same platform and translated into control commands to individual heat pumps.

Viessmann managed forecasting, aggregation and device control throughout. The result: reliable, automated load shifting that reduced grid bottlenecks without interrupting heat supply to households.

'With ViFlex, we have demonstrated that heat pumps in residential buildings can be controlled flexibly, fully automatically, and without any loss of comfort,' said Janosch Balke, Product Manager Energy Services at Viessmann Climate Solutions. 'This makes it easier for households to contribute to the energy transition while actively stabilising the grid.'

The project partners are now advocating for the regulatory consolidation in Germany of what they term Redispatch 3.0 – moving from the current cost-based framework to a market-based approach in which households can voluntarily participate in congestion management using heat pumps, home battery storage or electric vehicles.

A pilot relevant to the UK

That direction maps directly onto the policy trajectory emerging in the UK. The Smart Secure Electricity Systems (SSES) initiative – a joint programme from DESNZ and Ofgem – is developing the regulatory framework to govern smart domestic energy appliances, including heat pumps and EV chargers, that participate in flexibility services. SSES is expected to introduce requirements for smart capabilities to enable consumer-led flexibility (CLF) and introduces a licensing regime for load controllers – the intermediaries responsible for aggregating and dispatching demand-side flexibility. The ViFlex model, in which Viessmann acts as aggregator and controller within a regulated TSO framework,aligns closely with the type of architecture that SSES proposals are intended to address.

Peter Spurway, head of key accounts & strategic partnerships, at Viessmann Climate Solutions UK, said: 'There are similar concepts being trialled in the UK, but what makes the ViFlex project particularly significant is that it is backed by almost three years of operational data from real homes under real conditions – not modelling, not a short-term test. That is a meaningfully different evidential base.

'Viessmann is well placed for what is coming in the UK market. We have the products – our Vitocal heat pump range is already in UK homes – and critically, we have the APIs that enable the interoperability these systems require. The ability to connect heat pumps into aggregation platforms, respond to grid signals and do so without disrupting the end user is not a future capability for us. ViFlex demonstrates it working,” concluded Peter Spurway.

Viessmann will showcase the integration of heat pumps, battery storage, EV chargers and other assets into end-users’ Home Energy Management System (HEMS) of choice at InstallerSHOW, at the NEC, Birmingham, between June 23rd and 25th (Viessmann stand: 5D20).