Lower return temperature and more stability 

Viborg Varme and Kamstrup began a collaboration in June 2024, to optimize the utility company’s return temperature by using a novel service, called Return Temperature Optimizer (RTO). Under the conditions of the service Kamstrup continuously monitors the return temperature in the district heating network and contacts customers that have outstanding consumption.

One year into the project, RTO has reduced the return temperature by 7.2 °C among the contacted consumers. In addition, the collaboration has removed a considerable number of tasks from the employees’ packed to-do lists. This definitely added to the company’s general stability, since its employees could spend more time on the daily operations to deliver greater value.

We interviewed John Vutborg, energy specialist at Viborg Varme, to show their perspective on the service. 

Viborg Varme, for the past 10 years, has proactively worked to lower the return temperature in the district heating network, continuously reaching out to those among their 12,652 active consumers (as of May 2025) who had the poorest heat extraction performance.

“We send emails to the large rental companies, where we paint a picture of their consumption and heat extraction and give them a hint about how they can solve the problem. If there was a particularly poor heat extraction performance or perhaps a bypass, then I either called them or, in worst case scenario, I had to visit them. In that way, I could easily end up with 3–4 visits in a week.”

It was an ambivalent task because, on the one hand, the effort brought great value, while on the other hand, it was a very time-consuming process.

“It definitely makes a big difference to focus on heat extraction, and it creates good value. But it has been a massive workload to maintain and follow up on, and it has taken a lot of time to handle that.” 

The effort to bring down the return temperature took quite some time from John Vutborg, but it was also a difficult task to keep strong focus on it, because unforeseen tasks often showed up our of the blue.

“As a rule of thumb, we dealt with return temperature related tasks on one of the first days of the month. But there was often an issue coming in that did not really go well with this project, and got us a bit off the track.”

At this point John particularly mentioned another project: converting natural gas users to a rented district heating setup. This took a large portion of their total work time and left much less focus on their return temperature efforts.

“We now have over 1,500 consumers with rental units. For customers who have been used to natural gas, district heating is typically a completely new world, and therefore they’re not as easy to help as other customers. So it’s a growing pile of tasks that is requiring more and more attention from us.”

By collaborating with Kamstrup, Viborg Varme has now gained more time to manage their project to convert natural gas users. At the same time, the RTO solution ensures that the return temperature work is carried out continuously.

“Now the effort to lower our return temperature takes up much less time in our own schedule, because with RTO we’ve reduced the workload by about a quarter.” 

RTO typically had the greatest impact among consumers that used an older district heating system. Here something has been always broken, and that caused heat consumption  skyrocketing.  

“It usually creates the biggest value, where something got broken in an older system, and the consumption rised to 10–20 cubic meters per day.”

Yet, RTO has also detected faults in newer systems that were not installed correctly.

“For example, it can happen with new installations in standard houses where the focus on properly adjusting and balancing the system was not quite sufficient. It’s a frustrating situation for a consumer because they just moved into a new house where the system doesn’t work optimally.”

Instead of bearing the responsibility themselves for monitoring their own consumption, customers now receive an email, in their official governmental mailbox, notifying them about any excessive consumption. This way, the customer can get a plumber to fix the issue before the heating bill would hit the sky. 

Throughout the project the communication between Viborg Varme and Kamstrup went really smooth, and in this regard, John Vutborg also shares that the collaboration around the RTO solution has gone exactly as expected.

“We have received exactly what we were promised. I got the help I needed, and I get answers to any questions that come up. I really can’t think of anything negative to say. It’s a great solution.”

John Vutborg also speaks positively about the initial preparations, where there was close cooperation between the two parties to fine tune the solution before it was launched.

“We had a good process at the start, where our ideas were challenged and then plans were adapted along our original ideas and processes. We discussed how it should look like from the customers’ point of view before the project was set in motion.”