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Pilot project confirms RTO calculations for Thisted Varmeforsyning 

When Kamstrup presented calculations showing that Return Temperature Optimizer (RTO) can lower the return temperature in the district heating network, Danish district heating utility Thisted Forsyning wanted concrete evidence – and evidence they got. 

When you have ambitions of running a healthy supply for the benefit of the entire municipality, you need to do your homework properly and invest wisely. Thisted Varmeforsyning is a good example of this.

The well-run company focuses on ensuring stable low prices on district heating for its more than 8,000 customers in Thisted Municipality. To do this, you need to investigate new initiatives thoroughly before spending your money, so you can be absolutely sure they actually deliver.

When Kamstrup went to Thisted to present the Return Temperature Optimizer (RTO) solution, which promises significant savings on district heating operations, the utility wanted more knowledge before making their decision. 

Concrete evidence needed  

The Kamstrup salespeople presented an analysis of what the utility stood to achieve. The calculations were based on common physical and mathematical models and drew partly on the utility's own meter figures and partly on Kamstrup's experience from other utilities.

However, Thisted Varmeforsyning immediately took note of one small word: calculations. Before investing in the solution, they required concrete results from their own area confirming Kamstrup's calculations and proving RTO’s worth. 

 

What is RTO? 

 

RTO optimises the district heating network by collecting temperature data from the meters and using them to find installations with high return temperature. The system notifies affected consumers directly via e-Boks, a secure digital mailbox used in Denmark, so that the installation can be adjusted or repaired. The utility doesn’t need to do anything. 

Test project with 200 district heating meters 

To see if the calculations were correct, Thisted Varmeforsyning and Kamstrup agreed to run a pilot project in Hillerslev – a small town with almost 200 district heating meters about 8 km north of Thisted. The project was started at the end of February 2025 and ran for a month.

 

During the test period, the outside temperature remained stable. This made it easier to collect the data that would provide a true picture of RTO, because the plant in Thisted didn’t have to adjust the flow temperature.


Meter data almost identical to calculations 

 

After one month had passed, it became clear that Kamstrup's calculations were spot on. Not only had the return temperature in the main pipe fallen by about two degrees in agreement with Kamstrup’s calculations – the temperature data registered by Thisted Varmeforsyning's SCADA system matched Kamstrup’s calculations so accurately that the two temperature curves were almost identical. ntiske.

The curves for Kamstrup's calculations (orange) and Thisted Varmeforsyning's measurements (blue) during the test period are virtually identical. Kamstrup's figures show higher temperatures because they are based on measurements at each individual house, while the SCADA system registers the temperature in the main pipe, which is lower than at the houses due to the heat loss occurring between each house and the main pipe. 

The large temperature drop in just one month happened because of around 80 consumers in Hillerslev, who were notified by the RTO system during the project and decided to do something about their district heating installations immediately. A few consumers received two or three reminders, but most acted promptly. 

 

 Examples of data from household meters in Hillerslev where the return temperature (blue) dropped significantly after a reminder from the RTO system (vertical dotted line). 

The results are in line with Kamstrup's experience from other utilities: Many consumers are motivated to have their district heating systems optimised because they can save money or contribute to a more efficient heat supply. When plants run badly, it’s rarely out of indifference or ill will – people just don't know if something is wrong. With RTO, they are automatically notified. 

 

Savings and future-proofing

 

The results from Hillerslev mean that consumers save money from avoiding penalty fees. Thisted Varmeforsyning also achieves savings because they utilise their heat efficiently and can reduce the flow temperature. And because the tedious task of monitoring consumers has been placed in Kamstrup's hands, this frees up man-hours for more value-creating tasks – for example, advising plumbers on optimisation and balancing of citizens' district heating installations.

 

By lowering the flow temperature, Thisted Varmeforsyning are readying themselves for a future where district heating will increasingly be produced using low-emission methods, such as heat pumps or geothermal energy. If the flow temperature is too high, it will be very expensive to produce district heating with these methods. RTO helps the utility combine climate-friendly and cost-effective district heating production. 

 

Irrefutable proof 

 

In Hillerslev, Thisted Varmeforsyning and Kamstrup proved together that Kamstrup's calculations of RTO’s effect are to be trusted in a real operating scenario. Thisted Varmeforsyning got the tangible proof they needed, and at the time of writing, RTO is being rolled out in the rest of their network.

 

RTO has also given great results at other Danish utilities. Read more about the experiences from Sæby, Viborg and Solrød.

 

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