District heating networks are evolving to support the transition towards more sustainable and low-carbon energy systems. However, managing periods of high heat demand remains an important operational challenge. A recent case study by researchers from the Technical University of Denmark (DTU), in collaboration with Danfoss District Energy, explores how smarter control at building level could help address this issue without requiring additional hardware.
The study investigates a physics-based control strategy called Domestic Hot Water Peak Compensation (DHWPC), designed to reduce peak heat demand at district heating substations by coordinating domestic hot water (DHW) charging and space heating (SH).
Understanding the peak demand challenge
In district heating systems, demand is not constant throughout the day. Morning and evening periods often bring simultaneous increases in heating and domestic hot water consumption across buildings.
At building level, the charging of domestic hot water tanks can contribute to short but significant peaks in heat demand. When several buildings experience these peaks at similar times, the combined demand can put additional pressure on district heating networks.
These peaks can create network congestion, increase the need for available heating capacity and contribute to reliance on additional heat production, including fossil-fuel boilers during periods of high demand.
Conventional approaches may involve additional production capacity or thermal storage infrastructure. The study instead explores how existing building substation controls could be used to manage demand more effectively.
How does the DHW Peak Compensation strategy work?
The DHWPC strategy uses the charging of a building’s domestic hot water tank as an automatic trigger to temporarily interrupt the space heating supply.
When the system detects that the DHW tank is charging, the control logic temporarily pauses the space heating loop. Once charging is complete, normal space heating operation resumes.
The approach relies on the thermal inertia of the building and its heating system. Since domestic hot water charging events are generally short, temporarily interrupting space heating is expected to have limited effects on indoor temperatures.
Unlike demand response strategies that depend on external signals, dynamic energy tariffs, forecasting or additional communication infrastructure, DHWPC uses locally available measurements within the substation.
This makes the approach relatively straightforward to integrate into existing substation control platforms, provided the necessary components and signals are available.
Testing the approach in a residential building
The strategy was evaluated through a field experiment in a multi-family residential building comprising 45 flats in Sønderborg, Denmark.
The test ran for 51 days, from February to April 2026, covering 228 analysed peak compensation events. Researchers monitored building heat demand, substation flow and indoor temperatures to assess the strategy’s performance.
The results showed:
- 33% reduction in peak building heat demand.
- 39% reduction in peak substation flow.
- No individual monitored apartment exceeded the ±1°C indoor temperature deviation band during the analysed events.
These findings indicate that coordinating domestic hot water charging with space heating can reduce short-term demand peaks while maintaining indoor thermal comfort within the monitored limits.
An important distinction, however, is that reducing peak demand does not necessarily mean reducing total energy consumption. The study recorded an 8.5% increase in the building’s weather-normalised total heat consumption compared with the reference period. This was mainly associated with the rebound effect, as the heating system compensated for the temporary interruption after each event.
Understanding and managing this rebound is therefore an important part of further developing the strategy.
Exploring the potential at district level
Beyond the individual building test, the researchers used simulation to investigate how the approach could perform across a larger district heating network.
The model represented a district of 50 residential buildings and examined the aggregated impact of applying DHWPC across the buildings.
The simulation indicated:
- 32% reduction in aggregated district peak heat demand.
- 17% reduction in peak network flow.
These results suggest that a control strategy implemented at individual building substations could also contribute to reducing peak demand at network level.
The study further examined different building typologies, showing that the potential for peak reduction depends on factors such as domestic hot water demand, tank size, charging flow rate and the relationship between domestic hot water and space heating consumption.
This highlights the importance of considering building characteristics when assessing where the approach could be most effective.
From research to practical application
One of the main points of interest is the possibility of using existing substation control infrastructure rather than relying on extensive hardware upgrades.
The approach could offer district heating operators another way to manage demand peaks, while potentially helping building owners reduce capacity-related costs where tariffs are linked to peak demand or flow.
However, further work is needed to address the rebound effect and assess the long-term impact of more frequent control actions on substation components, including valves, pumps and heat exchangers.
The findings provide a useful contribution to ongoing research into demand-side flexibility and the optimisation of district heating systems. They also illustrate how relatively simple control strategies can be explored to improve the operation of existing energy infrastructure.
Discover the research
The study, A Scalable Peak Shedding Solution for District Heating: Field Test, Simulation and Building Typology Analysis, was conducted by Reza Mokhtari, Jan Eric Thorsen and Rongling Li.
The manuscript is available as a preprint on SSRN:
The research acknowledges support from the European Commission through the SEEDS project (Grant Agreement No. 101138211), alongside other supporting programmes.
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